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  • richardmitnick 10:59 am on August 5, 2021 Permalink | Reply
    Tags: "How particle detectors capture matter’s hidden and beautiful reality", , , , , Fermi National Accelerator Laboratory DUNE/LBNF experiment (US)., FNAL Tevatron, , , , , , , W and Z bosons   

    From “Science News (US) : “How particle detectors capture matter’s hidden and beautiful reality” 

    From “Science News (US)

    Emily Conover

    Subatomic particles become visible as graceful arcs and whorls in bubble chambers (this image from 1978) and other detectors. Credit: DOE (US) Fermi National Accelerator Laboratory.

    At every moment, subatomic particles stream in unfathomable numbers through your body. Each second, about 100 billion neutrinos from the sun pass through your thumbnail, and you’re bathed in a rain of muons, birthed in Earth’s atmosphere. Even humble bananas emit positrons, the electron’s antimatter counterpart. A whole universe of particles exists, and we are mostly oblivious, largely because these particles are invisible.

    When I first learned, as a teenager, that this untold world of particles existed, I couldn’t stop thinking about it. And when I thought about it, I could barely breathe. I was, to steal a metaphor from writer David Foster Wallace, a fish who has only just noticed she’s swimming in water. The revelation that we’re stewing in a particle soup is why I went on to study physics, and eventually, to write about it.

    To truly fathom matter at its most fundamental level, people must be able to visualize this hidden world. That’s where particle detectors come in. They spot traces of the universe’s most minuscule constituents, making these intangible concepts real. What’s more, particle detectors reveal beauty: Particles leave behind graceful spirals of bubbles, flashes of light and crisp lines of sparks.

    Tracks from bubble chambers and cloud chambers typically had to be inspected by eye. In this June 1984 image, Renee Jones, a bubble chamber scanner working at Fermilab, measures the details of the tracks, including length and curvature.Credit: David Parker/Science Source(US).

    As a physics student, I spent hours examining these stunning pictures in my textbooks. I went on to build particle detectors in graduate school, and to make my own images of particles wending their way through our world.

    As a particle moves through a material, it drops bread crumbs that can give away its path. Those bread crumbs come in a variety of forms: light, heat or electric charge. “Basically, every particle detector that exists is looking for one or more of those three things,” says particle physicist Jennifer Raaf of Fermilab in Batavia, Ill. Particle detectors translate the bread crumbs into signals that can be recorded and analyzed. Such signals helped reveal the physics of the standard model, a crowning achievement of science that describes the particles and forces of nature. They’re also likely to be key in the discovery of physics beyond the standard model.

    As time has passed, technologies for detecting particles have vastly improved. Here are a few types of detectors that have made the invisible visible.

    Through a cloud

    One of the first ways scientists visualized particle tracks was with cloud chambers. Developed more than a century ago, cloud chambers are filled with a gas — often a vapor of alcohol — on the verge of condensing into liquid. When a charged particle passes through the chamber, it strips electrons from the air within, creating an electric charge that initiates condensation. A wispy line forms along the particle’s path, like a miniature contrail.

    A particle track in a cloud chamber in the early 1930s was the first evidence of a positron, a positively charged particle with the mass of an electron. In 1928, Paul Dirac published a paper proposing that electrons can have both a positive and negative charge. This paper introduced the Dirac equation. The track is curved due to a magnetic field that surrounded the chamber. Credit: C. D. Anderson, courtesy of Emilio Segrè Visual Archives | American Institute of Physics (US)

    Scientists often surround cloud chambers and other detectors with a strong magnetic field, which bends particles’ paths into curves or spirals. Negatively charged particles curve in one direction, positive particles go the opposite way. Other details further characterize the particle: The amount of curvature indicates a particle’s momentum, for example.

    Cloud chambers revealed a variety of previously unknown particles, including the positron and the muon, a heavy cousin of the electron, in the 1930s. These particles were mostly unexpected. At the time, physicists were barely coming to grips with the fact that particles besides electrons and protons existed.

    In this 1948 image, physicist Clifford Butler (center) is adjusting the instruments on a cloud chamber intended to track particles in cosmic rays. These showers of particles are produced when a high-energy particle from space slams into Earth’s atmosphere. Credit: Picture Post/Hulton Archive/Getty Images

    Bubble trails

    The 1950s were all about bubble chambers.

    When charged particles pass through liquid in a bubble chamber, they leave tiny vapor bubbles, like iridescent orbs trailing a soap bubble wand. Although the chambers are typically filled with liquid hydrogen, a variety of liquids can be used; one early prototype even used beer. Bubble chambers could be made bigger than cloud chambers, and produced sharper tracks, making it possible to observe more particles in more detail.

    A subatomic particle called a kaon decays into other particles that leave distinct spirals in this bubble chamber image from the 1970s. Credit: European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] [Europäische Organisation für Kernforschung](CH) [CERN].

    In the same decade, particle accelerators came to the fore. These accelerators produce energetic beams of particles that scientists can crash into other particles or into targets. Those collisions whip up a flurry of new particles. Scientists sent those beams into bubble chambers to watch what happened.

    The Big European Bubble Chamber, pictured during installation of the vessel, started up at CERN near Geneva in 1973.Credit: CERN.

    The resulting images were not only scientifically illuminating, they were stunning: If Raaf were going to get a tattoo, she says, it might be a bubble chamber image. I’ve so far resisted the temptation to get ink.

    Going digital

    Cloud chambers and bubble chambers had a drawback. Tracks were typically recorded with photographs, and each had to be inspected by eye for anything of interest. That process was too slow; it held physicists back from discovering the particles that might show up in only one or two out of myriad photographs, if that. To find the rarest of particles, “you can’t really be looking at pictures. You want to have that information digitized in a smart way,” says Sam Zeller, a particle physicist at Fermilab.

    In the UA1 detector at CERN near Geneva, high-voltage wires recorded the electric charge produced when incoming particles dislodged electrons from atoms in a gas-filled chamber. In this computer display, a proton and antiproton have collided and annihilated, producing new particles that traced out paths throughout the detector.Credit: Peter I.P. Kalmus, UA1 Experiment/Science Source.

    Enter the multiwire proportional chamber. Invented in 1968, this technology relies on a fine array of high-voltage wires, which record charge produced when incoming particles dislodge electrons from atoms in a gas-filled chamber. This technique could capture millions of particle tracks per second, much more than bubble chambers could achieve. And the data went directly to a computer for analysis. Multiwire proportional chambers and their descendants revolutionized particle physics, and led to discoveries of particles such as the charm quark and the gluon in the 1970s, and the W and Z bosons in the 1980s.

    CERN’s UA1 detector was active from 1981 until 1990; its most notable discoveries were the W and Z bosons, together with the UA2 experiment. This image shows a section of the experiment, strung with many fine wires, on display at the CERN museum. Credit: Mark Williamson/Wikimedia Commons (CC BY-SA 4.0).

    Some of the most advanced modern detectors trace their lineage back to multiwire proportional chambers, such as liquid argon time projection chambers. These detectors are high-resolution, meaning that researchers can zoom in on the details of an interaction and visualize it in 3-D. Liquid argon time projection chambers will be key to one of the biggest upcoming particle physics experiments in the United States, the Fermi National Accelerator Laboratory DUNE/LBNF experiment (US) in South Dakota. Because neutrinos very rarely interact with matter, the experiment demands such advanced detection techniques.

    Shining a light

    Scientists have also devised methods to detect particles via light. When a particle moves above a certain speed limit for a given material, it emits light, known as Čerenkov light. It’s analogous to an airplane passing the sound-speed barrier and creating a sonic boom. Charged particles can also emit light when passing through materials laced with certain chemicals, called scintillators.

    The NOvA experiment at Fermilab (US) uses tubes of liquid scintillator to spot neutrinos interacting inside the detector. In this image of data from the detector, a neutrino, which enters from the left, produces a spurt of charged particles. The neutrino is not visible, due to its lack of electric charge. Credit: NOvA/Fermilab.

    To spot the small amounts of light left behind by individual particles, scientists use photomultiplier tubes, originally invented in the 1930s, which convert light into electrical signals. These tubes could be used to pick up either Čerenkov light or scintillator light.

    Scintillator detectors began to prove their worth in 1956 when a tank of liquid scintillator was used to discover the neutrino — once thought to be entirely undetectable. Liquid scintillator detectors are still common — used in the NOvA neutrino experiment at Fermilab, for example — as are detectors made of solid plastic strips with scintillator mixed in.

    The NOvA neutrino experiment at Fermilab uses two detectors, this one located in Minnesota, made up of hundreds of thousands of PVC tubes filled with liquid scintillator. Credit: Justinvasel/Wikimedia Commons (CC BY-SA 4.0).

    Putting it all together

    The Tevatron was a circular particle accelerator (active until 2011) in the United States, at the Fermi National Accelerator Laboratory (also known as Fermilab), east of Batavia, Illinois, and is the second highest energy particle collider ever built, after the Large Hadron Collider (LHC) of the European Organization for Nuclear Research (CERN) near Geneva, Switzerland. The Tevatron was a synchrotron that accelerated protons and antiprotons in a 6.28 km (3.90 mi) ring to energies of up to 1 TeV, hence its name. The Tevatron was completed in 1983 at a cost of $120 million and significant upgrade investments were made during its active years of 1983–2011.

    The main achievement of the Tevatron was the discovery in 1995 of the top quark—the last fundamental fermion predicted by the Standard Model of particle physics. On July 2, 2012, scientists of the CDF and DØ collider experiment teams at Fermilab announced the findings from the analysis of around 500 trillion collisions produced from the Tevatron collider since 2001, and found that the existence of the suspected Higgs boson was highly likely with a confidence of 99.8%, later improved to over 99.9%.

    The Tevatron ceased operations on 30 September 2011, due to budget cuts and because of the completion of the LHC, which began operations in early 2010 and is far more powerful (planned energies were two 7 TeV beams at the LHC compared to 1 TeV at the Tevatron). The main ring of the Tevatron will probably be reused in future experiments, and its components may be transferred to other particle accelerators.



    Modern detectors at the world’s major particle colliders, like the detectors at the Large Hadron Collider at CERN near Geneva, throw in a bit of everything. “It’s this onion of different types of detectors; every layer is a different thing,” Raaf says.









    Standing multiple stories tall, these massive machines include an assortment of technologies — plastic scintillator detectors, Cherenkov detectors, descendants of multiwire proportional chambers. They also typically include detectors made from silicon that can precisely measure particle tracks based on small electric currents produced when particle pass through. These detectors all work in concert within a very strong magnet. After particles collide at the center of the detector, computers crunch the data from all the parts and reconstruct what happened in the collision, tracing out the paths the particles took.

    No matter the technique, the mesmerizing subatomic hieroglyphs allow physicists to decipher the native language of matter, unveiling its constituents and the forces by which they communicate. “It’s pretty amazing that you can see the invisible,” says Zeller.

    See the full article here .


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  • richardmitnick 8:25 pm on July 18, 2021 Permalink | Reply
    Tags: "Curiosity and technology drive quest to reveal fundamental secrets of the universe", A very specific particle called a J/psi might provide a clearer picture of what’s going on inside a proton’s gluonic field., , Argonne-driven technology is part of a broad initiative to answer fundamental questions about the birth of matter in the universe and the building blocks that hold it all together., , , , , , Computational Science, , , , , , Developing and fabricating detectors that search for signatures from the early universe or enhance our understanding of the most fundamental of particles., , Electron-Ion Collider (EIC) at DOE's Brookhaven National Laboratory (US) to be built inside the tunnel that currently houses the Relativistic Heavy Ion Collider [RHIC]., Exploring the hearts of protons and neutrons, FNAL Tevatron, , Neutrinoless double beta decay can only happen if the neutrino is its own anti-particle., , , , , , , SLAC National Accelerator Laboratory(US), , ,   

    From DOE’s Argonne National Laboratory (US) : “Curiosity and technology drive quest to reveal fundamental secrets of the universe” 

    Argonne Lab

    From DOE’s Argonne National Laboratory (US)

    July 15, 2021
    John Spizzirri

    Argonne-driven technology is part of a broad initiative to answer fundamental questions about the birth of matter in the universe and the building blocks that hold it all together.

    Imagine the first of our species to lie beneath the glow of an evening sky. An enormous sense of awe, perhaps a little fear, fills them as they wonder at those seemingly infinite points of light and what they might mean. As humans, we evolved the capacity to ask big insightful questions about the world around us and worlds beyond us. We dare, even, to question our own origins.

    “The place of humans in the universe is important to understand,” said physicist and computational scientist Salman Habib. ​“Once you realize that there are billions of galaxies we can detect, each with many billions of stars, you understand the insignificance of being human in some sense. But at the same time, you appreciate being human a lot more.”

    The South Pole Telescope is part of a collaboration between Argonne and a number of national labs and universities to measure the CMB, considered the oldest light in the universe.

    The high altitude and extremely dry conditions of the South Pole keep water vapor from absorbing select light wavelengths.

    With no less a sense of wonder than most of us, Habib and colleagues at the U.S. Department of Energy’s (DOE) Argonne National Laboratory are actively researching these questions through an initiative that investigates the fundamental components of both particle physics and astrophysics.

    The breadth of Argonne’s research in these areas is mind-boggling. It takes us back to the very edge of time itself, to some infinitesimally small portion of a second after the Big Bang when random fluctuations in temperature and density arose, eventually forming the breeding grounds of galaxies and planets.

    It explores the heart of protons and neutrons to understand the most fundamental constructs of the visible universe, particles and energy once free in the early post-Big Bang universe, but later confined forever within a basic atomic structure as that universe began to cool.

    And it addresses slightly newer, more controversial questions about the nature of Dark Matter and Dark Energy, both of which play a dominant role in the makeup and dynamics of the universe but are little understood.
    Dark Energy Survey

    Dark Energy Camera [DECam] built at DOE’s Fermi National Accelerator Laboratory(US)

    NOIRLab National Optical Astronomy Observatory(US) Cerro Tololo Inter-American Observatory(CL) Victor M Blanco 4m Telescope which houses the Dark-Energy-Camera – DECam at Cerro Tololo, Chile at an altitude of 7200 feet.

    NOIRLab(US)NSF NOIRLab NOAO (US) Cerro Tololo Inter-American Observatory(CL) approximately 80 km to the East of La Serena, Chile, at an altitude of 2200 meters.

    Timeline of the Inflationary Universe WMAP

    The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

    According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

    DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

    Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.

    “And this world-class research we’re doing could not happen without advances in technology,” said Argonne Associate Laboratory Director Kawtar Hafidi, who helped define and merge the different aspects of the initiative.

    “We are developing and fabricating detectors that search for signatures from the early universe or enhance our understanding of the most fundamental of particles,” she added. ​“And because all of these detectors create big data that have to be analyzed, we are developing, among other things, artificial intelligence techniques to do that as well.”

    Decoding messages from the universe

    Fleshing out a theory of the universe on cosmic or subatomic scales requires a combination of observations, experiments, theories, simulations and analyses, which in turn requires access to the world’s most sophisticated telescopes, particle colliders, detectors and supercomputers.

    Argonne is uniquely suited to this mission, equipped as it is with many of those tools, the ability to manufacture others and collaborative privileges with other federal laboratories and leading research institutions to access other capabilities and expertise.

    As lead of the initiative’s cosmology component, Habib uses many of these tools in his quest to understand the origins of the universe and what makes it tick.

    And what better way to do that than to observe it, he said.

    “If you look at the universe as a laboratory, then obviously we should study it and try to figure out what it is telling us about foundational science,” noted Habib. ​“So, one part of what we are trying to do is build ever more sensitive probes to decipher what the universe is trying to tell us.”

    To date, Argonne is involved in several significant sky surveys, which use an array of observational platforms, like telescopes and satellites, to map different corners of the universe and collect information that furthers or rejects a specific theory.

    For example, the South Pole Telescope survey, a collaboration between Argonne and a number of national labs and universities, is measuring the cosmic microwave background (CMB) [above], considered the oldest light in the universe. Variations in CMB properties, such as temperature, signal the original fluctuations in density that ultimately led to all the visible structure in the universe.

    Additionally, the Dark Energy Spectroscopic Instrument and the forthcoming Vera C. Rubin Observatory are specially outfitted, ground-based telescopes designed to shed light on dark energy and dark matter, as well as the formation of luminous structure in the universe.

    DOE’s Lawrence Berkeley National Laboratory(US) DESI spectroscopic instrument on the Mayall 4-meter telescope at Kitt Peak National Observatory, in the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers 55 mi west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft).

    National Optical Astronomy Observatory (US) Mayall 4 m telescope at NSF NOIRLab NOAO Kitt Peak National Observatory (US) in the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers 55 mi west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft).

    National Science Foundation(US) NSF (US) NOIRLab NOAO Kitt Peak National Observatory on the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers (55 mi) west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft).

    National Science Foundation(US) NOIRLab (US) NOAO Kitt Peak National Observatory (US) on Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers (55 mi) west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft). annotated.

    NSF (US) NOIRLab (US) NOAO (US) Vera C. Rubin Observatory [LSST] Telescope currently under construction on the El Peñón peak at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing NSF (US) NOIRLab (US) NOAO (US) Gemini South Telescope and NSF (US) NOIRLab (US) NOAO (US) Southern Astrophysical Research Telescope.

    Darker matters

    All the data sets derived from these observations are connected to the second component of Argonne’s cosmology push, which revolves around theory and modeling. Cosmologists combine observations, measurements and the prevailing laws of physics to form theories that resolve some of the mysteries of the universe.

    But the universe is complex, and it has an annoying tendency to throw a curve ball just when we thought we had a theory cinched. Discoveries within the past 100 years have revealed that the universe is both expanding and accelerating its expansion — realizations that came as separate but equal surprises.

    Saul Perlmutter (center) [The Supernova Cosmology Project] shared the 2006 Shaw Prize in Astronomy, the 2011 Nobel Prize in Physics, and the 2015 Breakthrough Prize in Fundamental Physics with Brian P. Schmidt (right) and Adam Riess (left) [The High-z Supernova Search Team] for providing evidence that the expansion of the universe is accelerating.

    “To say that we understand the universe would be incorrect. To say that we sort of understand it is fine,” exclaimed Habib. ​“We have a theory that describes what the universe is doing, but each time the universe surprises us, we have to add a new ingredient to that theory.”

    Modeling helps scientists get a clearer picture of whether and how those new ingredients will fit a theory. They make predictions for observations that have not yet been made, telling observers what new measurements to take.

    Habib’s group is applying this same sort of process to gain an ever-so-tentative grasp on the nature of dark energy and dark matter. While scientists can tell us that both exist, that they comprise about 68 and 26% of the universe, respectively, beyond that not much else is known.


    Dark Matter Background
    Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, some 30 years later, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com.

    Coma cluster via NASA/ESA Hubble.

    In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.
    Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.
    Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science).

    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL).

    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970

    Dark Matter Research

    Inside the Axion Dark Matter eXperiment U Washington (US) Credit : Mark Stone U. of Washington. Axion Dark Matter Experiment.

    Observations of cosmological structure — the distribution of galaxies and even of their shapes — provide clues about the nature of dark matter, which in turn feeds simple dark matter models and subsequent predictions. If observations, models and predictions aren’t in agreement, that tells scientists that there may be some missing ingredient in their description of dark matter.

    But there are also experiments that are looking for direct evidence of dark matter particles, which require highly sensitive detectors [above]. Argonne has initiated development of specialized superconducting detector technology for the detection of low-mass dark matter particles.

    This technology requires the ability to control properties of layered materials and adjust the temperature where the material transitions from finite to zero resistance, when it becomes a superconductor. And unlike other applications where scientists would like this temperature to be as high as possible — room temperature, for example — here, the transition needs to be very close to absolute zero.

    Habib refers to these dark matter detectors as traps, like those used for hunting — which, in essence, is what cosmologists are doing. Because it’s possible that dark matter doesn’t come in just one species, they need different types of traps.

    “It’s almost like you’re in a jungle in search of a certain animal, but you don’t quite know what it is — it could be a bird, a snake, a tiger — so you build different kinds of traps,” he said.

    Lab researchers are working on technologies to capture these elusive species through new classes of dark matter searches. Collaborating with other institutions, they are now designing and building a first set of pilot projects aimed at looking for dark matter candidates with low mass.

    Tuning in to the early universe

    Amy Bender is working on a different kind of detector — well, a lot of detectors — which are at the heart of a survey of the cosmic microwave background (CMB).

    “The CMB is radiation that has been around the universe for 13 billion years, and we’re directly measuring that,” said Bender, an assistant physicist at Argonne.

    The Argonne-developed detectors — all 16,000 of them — capture photons, or light particles, from that primordial sky through the aforementioned South Pole Telescope, to help answer questions about the early universe, fundamental physics and the formation of cosmic structures.

    Now, the CMB experimental effort is moving into a new phase, CMB-Stage 4 (CMB-S4).

    CMB-S4 is the next-generation ground-based cosmic microwave background experiment.With 21 telescopes at the South Pole and in the Chilean Atacama desert surveying the sky with 550,000 cryogenically-cooled superconducting detectors for 7 years, CMB-S4 will deliver transformative discoveries in fundamental physics, cosmology, astrophysics, and astronomy. CMB-S4 is supported by the Department of Energy Office of Science and the National Science Foundation.

    This larger project tackles even more complex topics like Inflationary Theory, which suggests that the universe expanded faster than the speed of light for a fraction of a second, shortly after the Big Bang.

    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation
    [caption id="attachment_55311" align="alignnone" width="632"] HPHS Owls

    Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes
    Alex Mittelmann, Coldcreation

    Alan Guth’s notes:

    Alan Guth’s original notes on inflation


    A section of a detector array with architecture suitable for future CMB experiments, such as the upcoming CMB-S4 project. Fabricated at Argonne’s Center for Nanoscale Materials, 16,000 of these detectors currently drive measurements collected from the South Pole Telescope. (Image by Argonne National Laboratory.)

    While the science is amazing, the technology to get us there is just as fascinating.

    Technically called transition edge sensing (TES) bolometers, the detectors on the telescope are made from superconducting materials fabricated at Argonne’s Center for Nanoscale Materials, a DOE Office of Science User Facility.

    Each of the 16,000 detectors acts as a combination of very sensitive thermometer and camera. As incoming radiation is absorbed on the surface of each detector, measurements are made by supercooling them to a fraction of a degree above absolute zero. (That’s over three times as cold as Antarctica’s lowest recorded temperature.)

    Changes in heat are measured and recorded as changes in electrical resistance and will help inform a map of the CMB’s intensity across the sky.

    CMB-S4 will focus on newer technology that will allow researchers to distinguish very specific patterns in light, or polarized light. In this case, they are looking for what Bender calls the Holy Grail of polarization, a pattern called B-modes.

    Capturing this signal from the early universe — one far fainter than the intensity signal — will help to either confirm or disprove a generic prediction of inflation.

    It will also require the addition of 500,000 detectors distributed among 21 telescopes in two distinct regions of the world, the South Pole and the Chilean desert. There, the high altitude and extremely dry conditions keep water vapor in the atmosphere from absorbing millimeter wavelength light, like that of the CMB.

    While previous experiments have touched on this polarization, the large number of new detectors will improve sensitivity to that polarization and grow our ability to capture it.

    “Literally, we have built these cameras completely from the ground up,” said Bender. ​“Our innovation is in how to make these stacks of superconducting materials work together within this detector, where you have to couple many complex factors and then actually read out the results with the TES. And that is where Argonne has contributed, hugely.”

    Down to the basics

    Argonne’s capabilities in detector technology don’t just stop at the edge of time, nor do the initiative’s investigations just look at the big picture.

    Most of the visible universe, including galaxies, stars, planets and people, are made up of protons and neutrons. Understanding the most fundamental components of those building blocks and how they interact to make atoms and molecules and just about everything else is the realm of physicists like Zein-Eddine Meziani.

    “From the perspective of the future of my field, this initiative is extremely important,” said Meziani, who leads Argonne’s Medium Energy Physics group. ​“It has given us the ability to actually explore new concepts, develop better understanding of the science and a pathway to enter into bigger collaborations and take some leadership.”

    Taking the lead of the initiative’s nuclear physics component, Meziani is steering Argonne toward a significant role in the development of the Electron-Ion Collider, a new U.S. Nuclear Physics Program facility slated for construction at DOE’s Brookhaven National Laboratory (US).

    Argonne’s primary interest in the collider is to elucidate the role that quarks, anti-quarks and gluons play in giving mass and a quantum angular momentum, called spin, to protons and neutrons — nucleons — the particles that comprise the nucleus of an atom.

    EIC Electron Animation, Inner Proton Motion.
    Electrons colliding with ions will exchange virtual photons with the nuclear particles to help scientists ​“see” inside the nuclear particles; the collisions will produce precision 3D snapshots of the internal arrangement of quarks and gluons within ordinary nuclear matter; like a combination CT/MRI scanner for atoms. (Image by Brookhaven National Laboratory.)

    While we once thought nucleons were the finite fundamental particles of an atom, the emergence of powerful particle colliders, like the Stanford Linear Accelerator Center at Stanford University and the former Tevatron at DOE’s Fermilab, proved otherwise.

    It turns out that quarks and gluons were independent of nucleons in the extreme energy densities of the early universe; as the universe expanded and cooled, they transformed into ordinary matter.

    “There was a time when quarks and gluons were free in a big soup, if you will, but we have never seen them free,” explained Meziani. ​“So, we are trying to understand how the universe captured all of this energy that was there and put it into confined systems, like these droplets we call protons and neutrons.”

    Some of that energy is tied up in gluons, which, despite the fact that they have no mass, confer the majority of mass to a proton. So, Meziani is hoping that the Electron-Ion Collider will allow science to explore — among other properties — the origins of mass in the universe through a detailed exploration of gluons.

    And just as Amy Bender is looking for the B-modes polarization in the CMB, Meziani and other researchers are hoping to use a very specific particle called a J/psi to provide a clearer picture of what’s going on inside a proton’s gluonic field.

    But producing and detecting the J/psi particle within the collider — while ensuring that the proton target doesn’t break apart — is a tricky enterprise, which requires new technologies. Again, Argonne is positioning itself at the forefront of this endeavor.

    “We are working on the conceptual designs of technologies that will be extremely important for the detection of these types of particles, as well as for testing concepts for other science that will be conducted at the Electron-Ion Collider,” said Meziani.

    Argonne also is producing detector and related technologies in its quest for a phenomenon called neutrinoless double beta decay. A neutrino is one of the particles emitted during the process of neutron radioactive beta decay and serves as a small but mighty connection between particle physics and astrophysics.

    “Neutrinoless double beta decay can only happen if the neutrino is its own anti-particle,” said Hafidi. ​“If the existence of these very rare decays is confirmed, it would have important consequences in understanding why there is more matter than antimatter in the universe.”

    Argonne scientists from different areas of the lab are working on the Neutrino Experiment with Xenon Time Projection Chamber (NEXT) collaboration to design and prototype key systems for the collaborative’s next big experiment. This includes developing a one-of-a-kind test facility and an R&D program for new, specialized detector systems.

    “We are really working on dramatic new ideas,” said Meziani. ​“We are investing in certain technologies to produce some proof of principle that they will be the ones to pursue later, that the technology breakthroughs that will take us to the highest sensitivity detection of this process will be driven by Argonne.”

    The tools of detection

    Ultimately, fundamental science is science derived from human curiosity. And while we may not always see the reason for pursuing it, more often than not, fundamental science produces results that benefit all of us. Sometimes it’s a gratifying answer to an age-old question, other times it’s a technological breakthrough intended for one science that proves useful in a host of other applications.

    Through their various efforts, Argonne scientists are aiming for both outcomes. But it will take more than curiosity and brain power to solve the questions they are asking. It will take our skills at toolmaking, like the telescopes that peer deep into the heavens and the detectors that capture hints of the earliest light or the most elusive of particles.

    We will need to employ the ultrafast computing power of new supercomputers. Argonne’s forthcoming Aurora exascale machine will analyze mountains of data for help in creating massive models that simulate the dynamics of the universe or subatomic world, which, in turn, might guide new experiments — or introduce new questions.

    Depiction of ANL ALCF Cray Intel SC18 Shasta Aurora exascale supercomputer, to be built at DOE’s Argonne National Laboratory.

    And we will apply artificial intelligence to recognize patterns in complex observations — on the subatomic and cosmic scales — far more quickly than the human eye can, or use it to optimize machinery and experiments for greater efficiency and faster results.

    “I think we have been given the flexibility to explore new technologies that will allow us to answer the big questions,” said Bender. ​“What we’re developing is so cutting edge, you never know where it will show up in everyday life.”

    Funding for research mentioned in this article was provided by Argonne Laboratory Directed Research and Development; Argonne program development; DOE Office of High Energy Physics: Cosmic Frontier, South Pole Telescope-3G project, Detector R&D; and DOE Office of Nuclear Physics.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    DOE’s Argonne National Laboratory (US) seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their is a science and engineering research national laboratory operated by UChicago Argonne LLC for the United States Department of Energy. The facility is located in Lemont, Illinois, outside of Chicago, and is the largest national laboratory by size and scope in the Midwest.

    Argonne had its beginnings in the Metallurgical Laboratory of the University of Chicago, formed in part to carry out Enrico Fermi’s work on nuclear reactors for the Manhattan Project during World War II. After the war, it was designated as the first national laboratory in the United States on July 1, 1946. In the post-war era the lab focused primarily on non-weapon related nuclear physics, designing and building the first power-producing nuclear reactors, helping design the reactors used by the United States’ nuclear navy, and a wide variety of similar projects. In 1994, the lab’s nuclear mission ended, and today it maintains a broad portfolio in basic science research, energy storage and renewable energy, environmental sustainability, supercomputing, and national security.

    UChicago Argonne, LLC, the operator of the laboratory, “brings together the expertise of the University of Chicago (the sole member of the LLC) with Jacobs Engineering Group Inc.” Argonne is a part of the expanding Illinois Technology and Research Corridor. Argonne formerly ran a smaller facility called Argonne National Laboratory-West (or simply Argonne-West) in Idaho next to the Idaho National Engineering and Environmental Laboratory. In 2005, the two Idaho-based laboratories merged to become the DOE’s Idaho National Laboratory.
    What would become Argonne began in 1942 as the Metallurgical Laboratory at the University of Chicago, which had become part of the Manhattan Project. The Met Lab built Chicago Pile-1, the world’s first nuclear reactor, under the stands of the University of Chicago sports stadium. Considered unsafe, in 1943, CP-1 was reconstructed as CP-2, in what is today known as Red Gate Woods but was then the Argonne Forest of the Cook County Forest Preserve District near Palos Hills. The lab was named after the surrounding forest, which in turn was named after the Forest of Argonne in France where U.S. troops fought in World War I. Fermi’s pile was originally going to be constructed in the Argonne forest, and construction plans were set in motion, but a labor dispute brought the project to a halt. Since speed was paramount, the project was moved to the squash court under Stagg Field, the football stadium on the campus of the University of Chicago. Fermi told them that he was sure of his calculations, which said that it would not lead to a runaway reaction, which would have contaminated the city.

    Other activities were added to Argonne over the next five years. On July 1, 1946, the “Metallurgical Laboratory” was formally re-chartered as Argonne National Laboratory for “cooperative research in nucleonics.” At the request of the U.S. Atomic Energy Commission, it began developing nuclear reactors for the nation’s peaceful nuclear energy program. In the late 1940s and early 1950s, the laboratory moved to a larger location in unincorporated DuPage County, Illinois and established a remote location in Idaho, called “Argonne-West,” to conduct further nuclear research.

    In quick succession, the laboratory designed and built Chicago Pile 3 (1944), the world’s first heavy-water moderated reactor, and the Experimental Breeder Reactor I (Chicago Pile 4), built-in Idaho, which lit a string of four light bulbs with the world’s first nuclear-generated electricity in 1951. A complete list of the reactors designed and, in most cases, built and operated by Argonne can be viewed in the, Reactors Designed by Argonne page. The knowledge gained from the Argonne experiments conducted with these reactors 1) formed the foundation for the designs of most of the commercial reactors currently used throughout the world for electric power generation and 2) inform the current evolving designs of liquid-metal reactors for future commercial power stations.

    Conducting classified research, the laboratory was heavily secured; all employees and visitors needed badges to pass a checkpoint, many of the buildings were classified, and the laboratory itself was fenced and guarded. Such alluring secrecy drew visitors both authorized—including King Leopold III of Belgium and Queen Frederica of Greece—and unauthorized. Shortly past 1 a.m. on February 6, 1951, Argonne guards discovered reporter Paul Harvey near the 10-foot (3.0 m) perimeter fence, his coat tangled in the barbed wire. Searching his car, guards found a previously prepared four-page broadcast detailing the saga of his unauthorized entrance into a classified “hot zone”. He was brought before a federal grand jury on charges of conspiracy to obtain information on national security and transmit it to the public, but was not indicted.

    Not all nuclear technology went into developing reactors, however. While designing a scanner for reactor fuel elements in 1957, Argonne physicist William Nelson Beck put his own arm inside the scanner and obtained one of the first ultrasound images of the human body. Remote manipulators designed to handle radioactive materials laid the groundwork for more complex machines used to clean up contaminated areas, sealed laboratories or caves. In 1964, the “Janus” reactor opened to study the effects of neutron radiation on biological life, providing research for guidelines on safe exposure levels for workers at power plants, laboratories and hospitals. Scientists at Argonne pioneered a technique to analyze the moon’s surface using alpha radiation, which launched aboard the Surveyor 5 in 1967 and later analyzed lunar samples from the Apollo 11 mission.

    In addition to nuclear work, the laboratory maintained a strong presence in the basic research of physics and chemistry. In 1955, Argonne chemists co-discovered the elements einsteinium and fermium, elements 99 and 100 in the periodic table. In 1962, laboratory chemists produced the first compound of the inert noble gas xenon, opening up a new field of chemical bonding research. In 1963, they discovered the hydrated electron.

    High-energy physics made a leap forward when Argonne was chosen as the site of the 12.5 GeV Zero Gradient Synchrotron, a proton accelerator that opened in 1963. A bubble chamber allowed scientists to track the motions of subatomic particles as they zipped through the chamber; in 1970, they observed the neutrino in a hydrogen bubble chamber for the first time.

    Meanwhile, the laboratory was also helping to design the reactor for the world’s first nuclear-powered submarine, the U.S.S. Nautilus, which steamed for more than 513,550 nautical miles (951,090 km). The next nuclear reactor model was Experimental Boiling Water Reactor, the forerunner of many modern nuclear plants, and Experimental Breeder Reactor II (EBR-II), which was sodium-cooled, and included a fuel recycling facility. EBR-II was later modified to test other reactor designs, including a fast-neutron reactor and, in 1982, the Integral Fast Reactor concept—a revolutionary design that reprocessed its own fuel, reduced its atomic waste and withstood safety tests of the same failures that triggered the Chernobyl and Three Mile Island disasters. In 1994, however, the U.S. Congress terminated funding for the bulk of Argonne’s nuclear programs.

    Argonne moved to specialize in other areas, while capitalizing on its experience in physics, chemical sciences and metallurgy. In 1987, the laboratory was the first to successfully demonstrate a pioneering technique called plasma wakefield acceleration, which accelerates particles in much shorter distances than conventional accelerators. It also cultivated a strong battery research program.

    Following a major push by then-director Alan Schriesheim, the laboratory was chosen as the site of the Advanced Photon Source, a major X-ray facility which was completed in 1995 and produced the brightest X-rays in the world at the time of its construction.

    On 19 March 2019, it was reported in the Chicago Tribune that the laboratory was constructing the world’s most powerful supercomputer. Costing $500 million it will have the processing power of 1 quintillion flops. Applications will include the analysis of stars and improvements in the power grid.

    With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

    About the Advanced Photon Source

    The U. S. Department of Energy Office of Science’s Advanced Photon Source (APS) at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. The APS provides high-brightness X-ray beams to a diverse community of researchers in materials science, chemistry, condensed matter physics, the life and environmental sciences, and applied research. These X-rays are ideally suited for explorations of materials and biological structures; elemental distribution; chemical, magnetic, electronic states; and a wide range of technologically important engineering systems from batteries to fuel injector sprays, all of which are the foundations of our nation’s economic, technological, and physical well-being. Each year, more than 5,000 researchers use the APS to produce over 2,000 publications detailing impactful discoveries, and solve more vital biological protein structures than users of any other X-ray light source research facility. APS scientists and engineers innovate technology that is at the heart of advancing accelerator and light-source operations. This includes the insertion devices that produce extreme-brightness X-rays prized by researchers, lenses that focus the X-rays down to a few nanometers, instrumentation that maximizes the way the X-rays interact with samples being studied, and software that gathers and manages the massive quantity of data resulting from discovery research at the APS.

    With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

    About the Advanced Photon Source

    The U. S. Department of Energy Office of Science’s Advanced Photon Source (APS) at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. The APS provides high-brightness X-ray beams to a diverse community of researchers in materials science, chemistry, condensed matter physics, the life and environmental sciences, and applied research. These X-rays are ideally suited for explorations of materials and biological structures; elemental distribution; chemical, magnetic, electronic states; and a wide range of technologically important engineering systems from batteries to fuel injector sprays, all of which are the foundations of our nation’s economic, technological, and physical well-being. Each year, more than 5,000 researchers use the APS to produce over 2,000 publications detailing impactful discoveries, and solve more vital biological protein structures than users of any other X-ray light source research facility. APS scientists and engineers innovate technology that is at the heart of advancing accelerator and light-source operations. This includes the insertion devices that produce extreme-brightness X-rays prized by researchers, lenses that focus the X-rays down to a few nanometers, instrumentation that maximizes the way the X-rays interact with samples being studied, and software that gathers and manages the massive quantity of data resulting from discovery research at the APS.

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    Argonne Lab Campus

  • richardmitnick 12:54 pm on July 13, 2021 Permalink | Reply
    Tags: "Plasma Particle Accelerators Could Find New Physics", , Accelerators come in two shapes: circular (synchrotron) or linear (linac)., At the start of the 20th century scientists had little knowledge of the building blocks that form our physical world., , By the end of the century they had discovered not just all the elements that are the basis of all observed matter but a slew of even more fundamental particles that make up our cosmos., CERN CLIC collider, CERN is proposing a 100-kilometer-circumference electron-positron and proton-proton collider called the Future Circular Collider., , FNAL Tevatron, , , International Linear Collider (ILC), , , , Plasma is often called the fourth state of matter., , ,   

    From Scientific American (US) : “Plasma Particle Accelerators Could Find New Physics” 

    From Scientific American (US)

    July 2021
    Chandrashekhar Joshi

    Credit: Peter and Maria Hoey.

    At the start of the 20th century scientists had little knowledge of the building blocks that form our physical world. By the end of the century they had discovered not just all the elements that are the basis of all observed matter but a slew of even more fundamental particles that make up our cosmos, our planet and ourselves. The tool responsible for this revolution was the particle accelerator.

    The pinnacle achievement of particle accelerators came in 2012, when the Large Hadron Collider (LHC) uncovered the long-sought Higgs boson particle.

    The LHC is a 27-kilometer accelerating ring that collides two beams of protons with seven trillion electron volts (TeV) of energy each at CERN near Geneva.

    It is the biggest, most complex and arguably the most expensive scientific device ever built. The Higgs boson was the latest piece in the reigning theory of particle physics called the Standard Model. Yet in the almost 10 years since that discovery, no additional particles have emerged from this machine or any other accelerator.

    Have we found all the particles there are to find? Doubtful. The Standard Model of particle physics does not account for dark matter—particles that are plentiful yet invisible in the universe. A popular extension of the Standard Model called supersymmetry predicts many more particles out there than the ones we know about.

    And physicists have other profound unanswered questions such as: Are there extra dimensions of space? And why is there a great matter-antimatter imbalance in the observable universe? To solve these riddles, we will likely need a particle collider more powerful than those we have today.

    Many scientists support a plan to build the International Linear Collider (ILC), a straight-line-shaped accelerator that will produce collision energies of 250 billion (giga) electron volts (GeV).

    Though not as powerful as the LHC, the ILC would collide electrons with their antimatter counterparts, positrons—both fundamental particles that are expected to produce much cleaner data than the proton-proton collisions in the LHC. Unfortunately, the design of the ILC calls for a facility about 20 kilometers long and is expected to cost more than $10 billion—a price so high that no country has so far committed to host it.

    In the meantime, there are plans to upgrade the energy of the LHC to 27 TeV in the existing tunnel by increasing the strength of the superconducting magnets used to bend the protons. Beyond that, CERN is proposing a 100-kilometer-circumference electron-positron and proton-proton collider called the Future Circular Collider.

    Such a machine could reach the unprecedented energy of 100 TeV in proton-proton collisions. Yet the cost of this project will likely match or surpass the ILC. Even if it is built, work on it cannot begin until the LHC stops operation after 2035.

    But these gargantuan and costly machines are not the only options. Since the 1980s physicists have been developing alternative concepts for colliders. Among them is one known as a plasma-based accelerator, which shows great promise for delivering a TeV-scale collider that may be more compact and much cheaper than machines based on the present technology.

    The Particle Zoo

    The story of particle accelerators began in 1897 at the Cavendish physics laboratory at the University of Cambridge (UK).

    There J. J. Thomson created the earliest version of a particle accelerator using a tabletop cathode-ray tube like the ones used in most television sets before flat screens. He discovered a negatively charged particle—the electron.

    Soon physicists identified the other two atomic ingredients—protons and neutrons—using radioactive particles as projectiles to bombard atoms. And in the 1930s came the first circular particle accelerator—a palm-size device invented by Ernest Lawrence called the cyclotron, which could accelerate protons to about 80 kilovolts.

    Ernest Lawrence’s First Cyclotron, 1930 Stock Photo – Alamy.

    Thereafter accelerator technology evolved rapidly, and scientists were able to increase the energy of accelerated charged particles to probe the atomic nucleus. These advances led to the discovery of a zoo of hundreds of subnuclear particles, launching the era of accelerator-based high-energy physics. As the energy of accelerator beams rapidly increased in the final quarter of the past century, the zoo particles were shown to be built from just 17 fundamental particles predicted by the Standard Model [above]. All of these, except the Higgs boson, had been discovered in accelerator experiments by the late 1990s. The Higgs’s eventual appearance [above] at the LHC made the Standard Model the crowning achievement of modern particle physics.

    Aside from being some of the most successful instruments of scientific discovery in history, accelerators have found a multitude of applications in medicine and in our daily lives. They are used in CT scanners, for x-rays of bones and for radiotherapy of malignant tumors. They are vital in food sterilization and for generating radioactive isotopes for myriad medical tests and treatments. They are the basis of x-ray free-electron lasers, which are being used by thousands of scientists and engineers to do cutting-edge research in physical, life and biological sciences.

    Scientist tests a prototype plasma accelerator at the Facility for Advanced Accelerator Experimental Tests (FACET) at the DOE’s SLAC National Accelerator Laboratory (US) in California. Credit: Brad Plummer and SLAC National Accelerator Laboratory.

    Accelerator Basics

    Accelerators come in two shapes: circular (synchrotron) or linear (linac). All are powered by radio waves or microwaves that can accelerate particles to near light speed. At the LHC, for instance, two proton beams running in opposite directions repeatedly pass through sections of so-called radio-frequency cavities spaced along the ring.

    Radio waves inside these cavities create electric fields that oscillate between positive and negative to ensure that the positively charged protons always feel a pull forward. This pull speeds up the protons and transfers energy to them. Once the particles have gained enough energy, magnetic lenses focus the proton beams to several very precise collision points along the ring. When they crash, they produce extremely high energy densities, leading to the birth of new, higher-mass particles.

    When charged particles are bent in a circle, however, they emit “synchrotron radiation.” For any given radius of the ring, this energy loss is far less for heavier particles such as protons, which is why the LHC is a proton collider. But for electrons the loss is too great, particularly as their energy increases, so future accelerators that aim to collide electrons and positrons must either be linear colliders or have very large radii that minimize the curvature and thus the radiation the electrons emit.

    The size of an accelerator complex for a given beam energy ultimately depends on how much radio-frequency power can be pumped into the accelerating structure before the structure suffers electrical breakdown. Traditional accelerators have used copper to build this accelerating structure, and the breakdown threshold has meant that the maximum energy that can be added per meter is between 20 million and 50 million electron volts (MeV). Accelerator scientists have experimented with new types of accelerating structures that work at higher frequencies, thereby increasing the electrical breakdown threshold. They have also been working on improving the strength of the accelerating fields within superconducting cavities that are now routinely used in both synchrotrons and linacs. These advances are important and will almost certainly be implemented before any paradigm-changing concepts disrupt the highly successful conventional accelerator technologies.

    Eventually other strategies may be necessary. In 1982 the U.S. Department of Energy’s program on high-energy physics started a modest initiative to investigate entirely new ways to accelerate charged particles. This program generated many ideas; three among them look particularly promising.

    The first is called two-beam acceleration. This scheme uses a relatively cheap but very high-charge electron pulse to create high-frequency radiation in a cavity and then transfers this radiation to a second cavity to accelerate a secondary electron pulse. This concept is being tested at CERN on a machine called the Compact Linear Collider (CLIC).

    Another idea is to collide muons, which are much heavier cousins to electrons. Their larger mass means they can be accelerated in a circle without losing as much energy to synchrotron radiation as electrons do. The downside is that muons are unstable particles, with a lifetime of two millionths of a second. They are produced during the decay of particles called pions, which themselves must be produced by colliding an intense proton beam with a special target. No one has ever built a muon accelerator, but there are die-hard proponents of the idea among accelerator scientists.

    Finally, there is plasma-based acceleration. The notion originated in the 1970s with John M. Dawson of the University of California-Los Angeles (US), who proposed using a plasma wake produced by an intense laser pulse or a bunch of electrons to accelerate a second bunch of particles 1,000 or even 10,000 times faster than conventional accelerators can. This concept came to be known as the plasma wakefield accelerator.


    It generated a lot of excitement by raising the prospect of miniaturizing these gigantic machines, much like the integrated circuit miniaturized electronics starting in the 1960s.

    The Fourth State of Matter

    Most people are familiar with three states of matter: solid, liquid and gas. Plasma is often called the fourth state of matter. Though relatively uncommon in our everyday experience, it is the most common state of matter in our universe. By some estimates more than 99 percent of all visible matter in the cosmos is in the plasma state—stars, for instance, are made of plasma. A plasma is basically an ionized gas with equal densities of electrons and ions. Scientists can easily form plasma in laboratories by passing electricity through a gas as in a common fluorescent tube.

    A plasma wakefield accelerator takes advantage of the kind of wake you can find trailing a motorboat or a jet plane. As a boat moves forward, it displaces water, which moves out behind the boat to form a wake. Similarly, a tightly focused but ultraintense laser pulse moving through a plasma at the speed of light can generate a relativistic wake (that is, a wake also propagating nearly at light speed) by exerting radiation pressure and displacing the plasma electrons out of its way. If, instead of a laser pulse, a high-energy, high-current electron bunch is sent through the plasma, the negative charge of these electrons can expel all the plasma electrons, which feel a repulsive force. The heavier plasma ions, which are positively charged, remain stationary. After the pulse passes by, the expelled electrons are attracted back toward the ions by the force between their negative and positive charges. The electrons move so quickly they overshoot the ions and then again feel a backward pull, setting up an oscillating wake. Because of the separation of the plasma electrons from the plasma ions, there is an electric field inside this wake.

    If a second “trailing” electron bunch follows the first “drive” pulse, the electrons in this trailing bunch can gain energy from the wake much in the same way an electron bunch is accelerated by the radio-frequency wave in a conventional accelerator. If there are enough electrons in the trailing bunch, they can absorb sufficient energy from the wake so as to dampen the electric field. Now all the electrons in the trailing bunch see a constant accelerating field and gain energy at the same rate, thereby reducing the energy spread of the beam.

    The main advantage of a plasma accelerator over other schemes is that electric fields in a plasma wake can easily be 1,000 times stronger than those in traditional radio-frequency cavities. Plus, a very significant fraction of the energy that the driver beam transfers to the wake can be extracted by the trailing bunch. These effects make a plasma wakefield-based collider potentially both more compact and cheaper than conventional colliders.

    The Future of Plasma

    Both laser- and electron-driven plasma wakefield accelerators have made tremendous progress in the past two decades. My own team at U.C.L.A. has carried out prototype experiments with SLAC National Accelerator Laboratory physicists at their Facility for Advanced Accelerator Experimental Tests (FACET) in Menlo Park, Calif.

    We injected both drive and trailing electron bunches with an initial energy of 20 GeV and found that the trailing electrons gained up to 9 GeV after traveling through a 1.3-meter-long plasma. We also achieved a gain of 4 GeV in a positron bunch using just a one-meter-long plasma in a proof-of-concept experiment. Several other labs around the world have used laser-driven wakes to produce multi-GeV energy gains in electron bunches.

    Plasma accelerator scientists’ ultimate goal is to realize a linear accelerator that collides tightly focused electron and positron, or electron and electron, beams with a total energy exceeding 1 TeV. To accomplish this feat, we would likely need to connect around 50 individual plasma accelerator stages in series, with each stage adding an energy of 10 GeV.

    Yet aligning and synchronizing the drive and the trailing beams through so many plasma accelerator stages to collide with the desired accuracy presents a huge challenge. The typical radius of the wake is less than one millimeter, and scientists must inject the trailing electron bunch with submicron accuracy. They must synchronize timing between the drive pulse and the trailing beam to less than a hundredth of a trillionth of one second. Any misalignment would lead to a degradation of the beam quality and a loss of energy as well as charge caused by oscillation of the electrons about the plasma wake axis. This loss shows up in the form of hard x-ray emission, known as betatron emission, and places a finite limit on how much energy we can obtain from a plasma accelerator.

    Other technical hurdles also stand in the way of immediately turning this idea into a collider. For instance, the primary figure of merit for a particle collider is the luminosity—basically a measure of how many particles you can squeeze through a given space in a given time. The luminosity multiplied by the cross section—or the chances that two particles will collide— tells you how many collisions of a particular kind per second you are likely to observe at a given energy. The desired luminosity for a 1-TeV electron-positron linear collider is 10^34 cm^–2s^–1. Achieving this luminosity would require the colliding beams to have an average power of 20 megawatts each—10^10 particles per bunch at a repetition rate of 10 kilohertz and a beam size at the collision point of tens of a billionth of a meter. To illustrate how difficult this is, let us focus on the average power requirement. Even if you could transfer energy from the drive beam to the accelerating beam with 50 percent efficiency, 20 megawatts of power will be left behind in the two thin plasma columns. Ideally we could partially recover this power, but it is far from a straightforward task.

    And although scientists have made substantial progress on the technology needed for the electron arm of a plasma-based linear collider, positron acceleration is still in its infancy. A decade of concerted basic science research will most likely be needed to bring positrons to the same point we have reached with electrons. Alternatively, we could collide electrons with electrons or even with protons, where one or both electron arms are based on a plasma wakefield accelerator. Another concept that scientists are exploring at CERN is modulating a many-centimeters-long proton bunch by sending it through a plasma column and using the accompanying plasma wake to accelerate an electron bunch.

    The future for plasma-based accelerators is uncertain but exciting. It seems possible that within a decade we could build 10-GeV plasma accelerators on a large tabletop for various scientific and commercial applications using existing laser and electron beam facilities. But this achievement would still put us a long way from realizing a plasma-based linear collider for new physics discoveries. Even though we have made spectacular experimental progress in plasma accelerator research, the beam parameters achieved to date are not yet what we would need for just the electron arm of a future electron-positron collider that operates at the energy frontier. Yet with the prospects for the International Linear Collider and the Future Circular Collider uncertain, our best bet may be to persist with perfecting an exotic technology that offers size and cost savings. Developing plasma technology is a scientific and engineering grand challenge for this century, and it offers researchers wonderful opportunities for taking risks, being creative, solving fascinating problems—and the tantalizing possibility of discovering new fundamental pieces of nature.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Scientific American (US) , the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.

  • richardmitnick 11:40 am on July 6, 2021 Permalink | Reply
    Tags: "The odd(eron) couple", , , , , FNAL Tevatron, FNAL Tevatron DØ detector, , , , ,   

    From Symmetry: “The odd(eron) couple” 

    Symmetry Mag

    From Symmetry

    Sarah Charley

    Scientists discovered a new particle by comparing data recorded at the LHC and the Tevatron.

    In 2018, physicist Carlos Avila received a thrilling request from an old colleague.

    “It was the type of call that every scientist wants to have,” says Avila, who is a professor at the University of The Andes [Universidad de los Andes] (COL).

    The TOTEM experiment at CERN near Geneva, Switzerland, had recently announced evidence for an elusive quasi-particle that had been a missing link in physicists’ understanding of protons.

    But according to physicist Christophe Royon, the “TOTEM data alone was not enough.” To get the complete picture, Royon, who is a physicist at the University of Kansas (US), wanted to revisit data from the DØ experiment at the Tevatron, a particle accelerator that operated between 1987 and 2011 at the DOE’s Fermi National Accelerator Laboratory (US).

    “It was very exciting that these old measurements we had published in 2012 were still very important and could still play a role in this ongoing research,” Avila says.

    Conducting a joint analysis with two experiments from different generations wasn’t easy. It required rewriting decades-old software and inventing a new way to compare different types of data. In the end, the collaboration led to the discovery of a new particle: the odderon.

    Past-generation accelerator

    The Tevatron and its two experiments—DØ and CDF—rose to fame in 1995 with the discovery of the top quark, the heaviest known fundamental particle.

    “It was really a high point,” says DØ co-spokesperson Paul Grannis. “Everybody was walking on air.”

    At the time of the top quark discovery, CERN was constructing a new particle accelerator, the Large Hadron Collider [above], designed to reach energies an order of magnitude greater than the Tevatron. As the name suggests, the LHC collides a type of subatomic particle called hadrons, usually protons. The Tevatron also used protons, but collided them with their antimatter equivalents, antiprotons.

    The LHC started colliding protons in March 2010. A year and a half later, operators at Fermilab threw a big red switch and reverentially ended operations at the Tevatron. Over the next few years, Grannis watched the DØ collaboration shrink from several hundred scientists to just a handful of active researchers.

    “The people move on,” Grannis says. “There is less and less memory of the details of the experiment.”

    Avila and Royon were among the physicists that transitioned from DØ at the Tevatron to experiments at the LHC. Before bidding adieu, Avila worked on one last paper that compared DØ’s results with the first data from the LHC’s TOTEM experiment. Even though the energies of the two accelerators were different, many theorists expected DØ and TOTEM’s results to look similar. But they didn’t.

    “The DØ paper said that—despite all possible interpretation—they did not have the same pattern as seen at the LHC,” says TOTEM spokesperson Simone Giani. “That paper was the spark that triggered us to see the possibility of working together.”

    When protons don’t collide

    DØ and TOTEM were both looking at patterns from a type of interaction called elastic scattering, in which fast-moving hadrons meet and exchange particles without breaking apart. Grannis likens it to two hockey players passing a heavy puck.

    “If Sam slides a big hockey puck to Flo, Sam is going to recoil when he throws it, and Flo will recoil when she catches it,” he says.

    Like the hockey players, the hadrons drift off course after passing the “puck.” Both DØ and TOTEM have specialized detectors a few hundred meters from the interaction points to capture the deflected “Sams” and “Flos.” By measuring their momenta and how much their trajectories changed, physicists can deduce the properties of the puck that passed between them.

    Gluons à la carte

    In the elastic scattering that DØ and TOTEM study, these subatomic pucks are almost exclusively gluons: force-carrying subatomic particles that live inside hadrons. Because of quantum mechanical conservation laws, the exchanged gluons must always clump with other gluons. Scientists study these gluon-clump exchanges to learn about the structure of matter.

    “Every time we turn on a new accelerator, we hope to reach a high enough energy to see the internal workings of protons,” Giani says. “There is this ambition to purely distill the effect of the gluons and not that of the quarks.”

    Scattering data had already revealed that gluons can clump in even numbers and move between passing hadrons. But scientists were unsure if this same principle would apply to clumps consisting of an odd number of gluons. Theorists predicted the existence of these odd-numbered clumps, which they called odderons, 50 years ago. But odderons had never been observed experimentally.

    An emerging puzzle

    When physicists build a new flagship accelerator, they almost always make a major leap in energy. But they also make other changes, such as what kinds of particles to use in the collider. Because of this, comparing scattering data from different generations of accelerators—such as the Tevatron and LHC—has been difficult.

    “It has been impossible to disentangle if the scattering discrepancies are because of the intrinsic differences between protons and antiprotons, or because the energy of the accelerator is different every time,” Giani says.

    But physicists realized that these discrepancies between the Tevatron and LHC might be a blessing and not a curse. In fact, they thought they could be essential for uncovering the odderon.

    The matter or antimatter nature of the colliding hadrons would be unimportant if odderons didn’t exist and all the gluon “pucks” contained an even number of gluons. But the identities of these hadronic “Sams” and “Flos” (and specifically, whether Sam and Flo are both made from matter, or whether one of them is made from antimatter) should influence how easily they can exchange odderons.

    “The cleanest way to observe the odderon would be to look for differences between proton-proton and proton-antiproton interactions,” says Royon. “And what is the only recently available data for proton-antiproton interactions? This is the Tevatron.”

    Blast from the past

    The plan for TOTEM to work with DØ solidified in 2018 over drinks at CERN’s Restaurant 1.

    “When we did a rough comparison [between the Tevatron and LHC results] on a piece of paper, we already saw some differences,” Royon says. “This was the starting point.”

    A few months later, Avila was remotely logging into his old Fermilab account and trying to access the approximately 20 gigabytes of Tevatron data that he and his colleagues had analyzed years earlier.

    “The first time we tried to look at the data, none of the codes that we were using 10 years ago were working,” Avila says. “The software was already obsolete. We had to restore all the software and put it together with newer versions.”

    Another big challenge was comparing the Tevatron data with the LHC data and compensating for the different energies of the two accelerators. “That was the tricky part,” Grannis says.

    The DØ and TOTEM researchers regularly met over Zoom to check in on their progress and discuss ideas for how they could compare their data in the same energy regime.

    “The DØ people were concentrating on extracting the best possible information from DØ data, and the TOTEM people were doing the same for TOTEM,” Royon says. “My job was to unify the two communities.”

    If the odderon didn’t exist, then DØ and TOTEM should have seen the same scattering patterns in their data after adjusting for the energy differences between the Tevatron and LHC. But no matter how they processed the data, the scattering patterns remained distinct.

    “We did many cross checks,” Royon says. “It took one year to make sure we were correct.”

    The discrepancy between the proton-proton and proton-antiproton data showed that these hadrons were passing a new kind of subatomic puck. When combined with the 2018 TOTEM analysis, they had a high enough statistical significance to claim a discovery: They had finally found the odderon.

    An international team of scientists worked on the research. The US contribution was funded by the Department of Energy (US) and the National Science Foundation (US). “This is definitely the result of hard work from hundreds of people originating from everywhere in the world,” Royon says.

    For Avila, the discovery was just one of the many bonuses associated with teaming up with his old DØ colleagues on this new project. “You build strong friendships while doing research,” he says. “Even if you don’t stay in touch closely, you know these people and you know that working with them is really exciting.”

    Avila also says this discovery shows the value of keeping the legacy of older experiments alive.

    “We shouldn’t forget about this old data,” Avila says. “It can still bring new details about how nature behaves. It has a good scientific value no matter how many years have passed.”

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 12:38 am on March 10, 2021 Permalink | Reply
    Tags: "Odderon discovered", , , , FNAL Tevatron, FNAL Tevatron DØ collaboration, , , ,   

    From CERN(CH) Courier and DOE’s Fermi National Accelerator Laboratory(US): “Odderon discovered” 

    From CERN(CH) Courier


    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    From DOE’s Fermi National Accelerator Laboratory(US) , an enduring source of strength for the US contribution to scientific research world wide.

    9 March 2021
    Matthew Chalmers

    Excavating odderons Part of the TOTEM installation in the LHC tunnel 220m downstream from the CMS experiment. Credit: M. Brice/CERN.


    The TOTEM collaboration at the LHC, in collaboration with the DØ collaboration at the former Tevatron collider at Fermilab, have announced the discovery of the odderon — an elusive three-gluon state predicted almost 50 years ago. The result was presented in a “discovery talk” on Friday 5 March during the LHC Forward Physics meeting at CERN, and follows the joint publication of a CERN/Fermilab science paper by TOTEM and DØ reporting the observation in December 2020.

    FNAL/Tevatron DØ detector

    “This result probes the deepest features of Quantum Chromodynamics, notably that gluons interact between themselves and that an odd number of gluons are able to be ‘colourless’, thus shielding the strong interaction,” says TOTEM spokesperson Simone Giani of CERN. “A notable feature of this work is that the results are produced by joining the LHC and Tevatron data at different energies.”

    States comprising two, three or more gluons are usually called “glueballs”, and are peculiar objects made only of the carriers of the strong force. The advent of quantum chromodynamics (QCD) led theorists to predict the existence of the odderon in 1973. Proving its existence has been a major experimental challenge, however, requiring detailed measurements of protons as they glance off one another in high-energy collisions.

    While most high-energy collisions cause protons to break into their constituent quarks and gluons, roughly 25% are elastic collisions where the protons remain intact but emerge on slightly different paths (deviating by around a millimetre over a distance of 200 m at the LHC). TOTEM measures these small deviations in proton-proton (pp) scattering using two detectors located 220 m on either side of the CMS experiment, while DØ employed a similar setup at the Tevatron proton-antiproton (pp̄) collider.

    Pomerons and odderons

    At low energies, differences in pp vs pp̄ scattering are due to the exchange of different virtual mesons. At multi-TeV energies, on the other hand, proton interactions are expected to be mediated purely by gluons. In particular, elastic scattering at low-momentum transfer and high energies has long been explained by the exchange of a pomeron — a colour-neutral virtual glueball made up of an even number of gluons.

    However, in 2018 TOTEM reported measurements at high energies that could not easily be explained by this traditional picture. Instead, a further QCD object seemed to be at play, supporting models in which a three-gluon compound, or one containing higher odd numbers of gluons, was being exchanged. The discrepancy came to light via measurements of a parameter called ρ, which represents the ratio of the real and imaginary parts of the forward elastic-scattering amplitude when there is minimal gluon exchange between the colliding protons and thus almost no deviation in their trajectories. The results were sufficient to claim evidence for the odderon, although not yet its definitive observation.

    The new work is based on a model-independent analysis of data at medium-range momenta transfer. The TOTEM and DØ teams compared LHC pp data (recorded at collision energies of 2.76, 7, 8 and 13 TeV and extrapolated to 1.96 TeV), with Tevatron pp̄ data measured at 1.96 TeV. The odderon would be expected to contribute with different signs to pp and pp̄ scattering. Supporting this picture, the two data sets disagree at the 3.4σ level, providing evidence for the t-channel exchange of a colourless, C-odd gluonic compound.

    “When combined with the ρ and total cross-section result at 13 TeV, the significance is in the range 5.2-5.7σ and thus constitutes the first experimental observation of the odderon,” said Christophe Royon of University of Kansas, who presented the results on behalf of DØ and TOTEM last week. “This is a major discovery by CERN/Fermilab.”

    In addition to the new TOTEM-DØ model-independent study, several theoretical papers based on data from the ISR, SPS, Tevatron and LHC, and model-dependent inputs, provide additional evidence supporting the conclusion that the odderon exists.

    The new work is based on a model-independent analysis of data at medium-range momenta transfer. The TOTEM and DØ teams compared LHC pp data (recorded at collision energies of 2.76, 7, 8 and 13 TeV and extrapolated to 1.96 TeV), with Tevatron pp̄ data measured at 1.96 TeV. The odderon would be expected to contribute with different signs to pp and pp̄ scattering. Supporting this picture, the two data sets disagree at the 3.4σ level, providing evidence for the t-channel exchange of a colourless, C-odd gluonic compound.

    “When combined with the ρ and total cross-section result at 13 TeV, the significance is in the range 5.2-5.7σ and thus constitutes the first experimental observation of the odderon,” said Christophe Royon of University of Kansas, who presented the results on behalf of DØ and TOTEM last week. “This is a major discovery by CERN/Fermilab.”

    In addition to the new TOTEM-DØ model-independent study, several theoretical papers based on data from the ISR, SPS, Tevatron and LHC, and model-dependent inputs, provide additional evidence supporting the conclusion that the odderon exists.

    See the full article here .

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    CERN/ATLAS detector


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  • richardmitnick 8:35 pm on August 29, 2019 Permalink | Reply
    Tags: "Forget About Electrons And Protons; The Unstable Muon Could Be The Future Of Particle Physics", , , , FNAL Tevatron, , MICE collaboration — which stands for Muon Ionization Cooling Experiment — continues to push this technology to new heights and may make a muon collider a real possibility for the future.,   

    From Ethan Siegel: “Forget About Electrons And Protons; The Unstable Muon Could Be The Future Of Particle Physics” 

    From Ethan Siegel
    Aug 29, 2019

    The particle tracks emanating from a high energy collision at the LHC in 2014 show the creation of many new particles. It’s only because of the high-energy nature of this collision that new masses can be created. (WIKIMEDIA COMMONS USER PCHARITO)

    Electron-positron or proton-proton colliders are all the rage. But the unstable muon might be the key to unlocking the next frontier.

    If you want to probe the frontiers of fundamental physics, you have to collide particles at very high energies: with enough energy that you can create the unstable particles and states that don’t exist in our everyday, low-energy Universe. So long as you obey the Universe’s conservation laws and have enough free energy at your disposal, you can create any massive particle (and/or its antiparticle) from that energy via Einstein’s E = mc².

    Traditionally, there have been two strategies to do this.

    Collide electrons moving in one direction with positrons moving in the opposite direction, tuning your beams to whatever energy corresponds to the mass of particles you wish to produce.
    Collide protons in one direction with either other protons or anti-protons in the other, reaching higher energies but creating a much messier, less controllable signal to extract.

    One Nobel Laureate, Carlo Rubbia, has called for physicists to build something entirely novel: a muon collider.

    Carlo Rubbia at the 62nd Lindau Nobel Laureate Meeting on July 4, 2012. Markus Pössel (user name: Mapos)

    It’s ambitious and presently impractical, but it just might be the future of particle physics.

    The particles and antiparticles of the Standard Model have now all been directly detected, with the last holdout, the Higgs Boson, falling at the LHC earlier this decade.

    Standard Model of Particle Physics

    CERN CMS Higgs Event

    CERN ATLAS Higgs Event

    All of these particles can be created at LHC energies, and the masses of the particles lead to fundamental constants that are absolutely necessary to describe them fully. These particles can be well-described by the physics of the quantum field theories underlying the Standard Model, but they do not describe everything, like dark matter. (E. SIEGEL / BEYOND THE GALAXY)

    Above, you can see the particles and antiparticles of the Standard Model, which have now all been discovered. The Large Hadron Collider (LHC) at CERN discovered the Higgs boson, the long-sought-after last holdout, earlier this decade.

    While there’s still much science left to be done at the LHC — it’s only taken 2% of all the data it will acquire by the end of the 2030s — particle physicists are already looking ahead to the next generation of future colliders.

    A hypothetical new accelerator, either a long linear one or one inhabiting a large tunnel beneath the Earth, could dwarf the sensitivity to new particles that prior and current colliders can achieve. Even at that, there’s no guarantee we’ll find anything new, but we’re certain to find nothing new if we fail to try. ILC collaboration

    All of the plans put forth involve scaled-up version of existing technologies that have been used in past and/or current accelerators. We know how to accelerate electrons, positrons, and protons in a straight line. We know how to bend them into a circle, and maximize both the energy of the collisions and the number of particles colliding per second. Larger, more energetic versions of existing technologies are the simplest approach.

    FNAL/Tevatron map

    CERN map

    Future Circular Collider (FCC) Larger LHC

    CERN FCC Future Circular Collider map

    CERN Future Circular Collider

    The scale of the proposed Future Circular Collider (FCC), compared with the LHC presently at CERN and the Tevatron, formerly operational at Fermilab. The Future Circular Collider is perhaps the most ambitious proposal for a next-generation collider to date, including both lepton and proton options as various phases of its proposed scientific programme. (PCHARITO / WIKIMEDIA COMMONS)

    Of course, there are both benefits and drawbacks to each method we could use. You can build a linear collider, but the energy you can reach is going to be limited by how powerfully you can impart energy to these particles per-unit-distance as well as how long you build your accelerator. The drawback is that, without a continuous injection of circulating particles, linear colliders have lower collision rates and take longer amounts of time to collect the same amount of data.

    The other main style of collider is the style currently used at CERN: circular colliders. Instead of only getting one continuous shot to accelerate your particles before giving them the opportunity to collide, you speed them up while bending them in a circle, adding more and more particles to each clockwise and counterclockwise beam with every revolution. You set up your detectors at designated collision points, and measure what comes out.

    A candidate Higgs event in the ATLAS detector. Note how even with the clear signatures and transverse tracks, there is a shower of other particles; this is due to the fact that protons are composite particles. This is only the case because the Higgs gives mass to the fundamental constituents that compose these particles. At high enough energies, the currently most-fundamental particles known may yet split apart themselves. (THE ATLAS COLLABORATION / CERN)

    CERN ATLAS Image Claudia Marcelloni

    This is the preferred method, so long as your tunnel is long enough and your magnets are strong enough, for both electron/positron and proton/proton colliders. Compared to linear colliders, with a circular collider, you get

    greater numbers of particles inside the beam at any one time,
    second and third and thousandth chances for particles that missed one another on the prior pass through,
    and much greater collision rates overall, particularly for lower-energy heavy particles like the Z-boson.

    In general, electron/positron colliders are better for precision studies of known particles, while proton/proton colliders are better for probing the energy frontier.

    A four-muon candidate event in the ATLAS detector at the Large Hadron Collider. The muon/anti-muon tracks are highlighted in red, as the long-lived muons travel farther than any other unstable particle. The energies achieved by the LHC are sufficient for creating Higgs bosons; previous electron-positron colliders could not achieve the necessary energies. (ATLAS COLLABORATION/CERN)

    In fact, if you compare the LHC — which collides protons with protons — with the previous collider in the same tunnel (LEP, which collided electrons with positrons), you’d find something that surprises most people: the particles inside LEP went much, much faster than the ones inside the LHC!

    CERN LEP Collider

    CERN LEP Collider

    Everything in this Universe is limited by the speed of light in a vacuum: 299,792,458 m/s. It’s impossible to accelerate any massive particle to that speed, much less past it. At the LHC, particles get accelerated up to extremely high energies of 7 TeV per particle. Considering that a proton’s rest energy is only 938 MeV (or 0.000938 TeV), it’s easy to see how it reaches a speed of 299,792,455 m/s.

    But the electrons and positrons at LEP went even faster: 299,792,457.9964 m/s. Yet despite these enormous speeds, they only reached energies of ~110 GeV, or 1.6% the energies achieved at the LHC.

    Let’s understand how colliding particles create new ones. First, the energy available for creating new particles — the “E” in E = mc² — comes from the center-of-mass energy of the two colliding particles. In a proton-proton collision, it’s the internal structures that collide: quarks and gluons. The energy of each proton is divided up among many constituent particles, and these particles zip around inside the proton as well. When two of them collide, the energy available for creating new particles might still be large (up to 2 or 3 TeV), but isn’t the full-on 14 TeV.

    But the electron-positron idea is a lot cleaner: they’re not composite particles, and they don’t have internal structure or energy divided among constituents. Accelerate an electron and positron to the same speed in opposite directions, and 100% of that energy goes into creating new particles. But it won’t be anywhere near 14 TeV.

    A number of the various lepton colliders, with their luminosity (a measure of the collision rate and the number of detections one can make) as a function of center-of-mass collision energy. Note that the red line, which is a circular collider option, offers many more collisions than the linear version, but gets less superior as energy increases. Beyond about 380 GeV, circular colliders cannot achieve those energies, and a linear collider like CLIC is the far superior option. (GRANADA STRATEGY MEETING SUMMARY SLIDES / LUCIE LINSSEN (PRIVATE COMMUNICATION))

    Even though electrons and positrons go much faster than protons do, the total amount of energy a particle possesses is determined by its speed and also its original mass. Even though the electrons and positrons are much closer to the speed of light, it takes nearly 2,000 of them to make up as much rest mass as a proton. They have a greater speed but a much lower rest mass, and hence, a lower energy overall.

    There’s a good physics reasons why, even with the same radius ring and the same strong magnetic fields to bend them into a circle, electrons won’t reach the same energy as protons: synchrotron radiation. When you accelerate a charged particle with a magnetic field, it gives off radiation, which means it carries energy away.

    Relativistic electrons and positrons can be accelerated to very high speeds, but will emit synchrotron radiation (blue) at high enough energies, preventing them from moving faster. This synchrotron radiation is the relativistic analog of the radiation predicted by Rutherford so many years ago, and has a gravitational analogy if you replace the electromagnetic fields and charges with gravitational ones. (CHUNG-LI DONG, JINGHUA GUO, YANG-YUAN CHEN, AND CHANG CHING-LIN, ‘SOFT-X-RAY SPECTROSCOPY PROBES NANOMATERIAL-BASED DEVICES’)

    The amount of energy radiated away is dependent on the field strength (squared), the energy of the particle (squared), but also on the inherent charge-to-mass ratio of the particle (to the fourth power). Since electrons and positrons have the same charge as the proton, but just 1/1836th of a proton’s mass, that synchrotron radiation is the limiting factor for electron-positron systems in a circular collider. You’d need a circular collider 100 km around just to be able to create a pair of top-antitop quarks in a next-generation particle accelerator using electrons and positrons.

    This is where the big idea of using muons comes in. Muons (and anti-muons) are the cousins of electrons (and positrons), being:

    fundamental (and not composite) particles,
    being 206 times as massive as an electron (with a much smaller charge-to-mass ratio and much less synchrotron radiation),
    and also, unlike electrons or positrons, being fundamentally unstable.

    That last difference is the present dealbreaker: muons have a mean lifetime of just 2.2 microseconds before decaying away.

    An earlier design plan (now defunct) for a full-scale muon-antimuon collider at Fermilab, the source of the world’s second-most powerful particle accelerator behind the LHC at CERN. (FERMILAB)

    In the future, however, we might be able to work around that anyway. You see, Einstein’s special relativity tells us that as particles move closer and closer to the speed of light, time dilates for that particle in the observer’s reference frame. In other words, if we make this muon move fast enough, we can dramatically increase the time it lives before decaying; this is the same physics behind why cosmic ray muons pass through us all the time!

    If we could accelerate a muon up to the same 6.5 TeV in energy that LHC protons achieved during their prior data-taking run, that muon would live for 135,000 microseconds instead of 2.2 microseconds: enough time to circle the LHC some 1,500 times before decaying away. If you could collide a muon/anti-muon pair at those speeds, you’d have 100% of that energy — all 13 TeV of it — available for particle creation.

    The prototype MICE 201-megahertz RF module, with the copper cavity mounted, is shown during assembly at Fermilab. This apparatus could focus and collimate a muon beam, enabling the muons to be accelerated and survive for much longer than 2.2 microseconds. (Y. TORUN / IIT / FERMILAB TODAY)

    Humanity can always choose to build a bigger ring or invest in producing stronger-field magnets; those are easy ways to go to higher energies in particle physics. But there’s no cure for synchrotron radiation with electrons and positrons; you’d have to use heavier particles instead. There’s no cure for energy being distributed among multiple constituent particles inside a proton; you’d have to use fundamental particles instead.

    The muon is the one particle that could solve both of these issues. The only drawback is that they’re unstable, and difficult to keep alive for a long time. However, they’re easy to make: smash a proton beam into a piece of acrylic and you’ll produce pions, which will decay into both muons and anti-muons. Accelerate those muons to high energy and collimate them into beams, and you can put them in a circular collider.

    While many unstable particles, both fundamental and composite, can be produced in particle physics, only protons, neutrons (bound in nuclei) and the electron are stable, along with their antimatter counterparts and the photon. Everything else is short-lived, but if muons can be kept at high enough speeds, they might live long enough to forge a next-generation particle collider out of. (CONTEMPORARY PHYSICS EDUCATION PROJECT (CPEP), U.S. DEPARTMENT OF ENERGY / NSF / LBNL)

    The MICE collaboration — which stands for Muon Ionization Cooling Experiment — continues to push this technology to new heights, and may make a muon collider a real possibility for the future. The goal is to reveal whatever secrets nature might have waiting in store for us, and these are secrets we cannot predict. As Carlo Rubbia himself said,

    “…these fundamental choices are coming from nature, not from individuals. Theorists can do what they like, but nature is the one deciding in the end….”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

  • richardmitnick 3:00 pm on September 4, 2018 Permalink | Reply
    Tags: , , , , FNAL Tevatron, , , , , ,   

    From University at Buffalo: “UB physicists awarded $1.45 million to study inner workings of the universe” 

    U Buffalo bloc.

    From University at Buffalo

    September 4, 2018
    Charlotte Hsu

    Photo illustration: Left to right: University at Buffalo physicists Avto Kharchilava, Ia Iashvili and Salvatore Rappoccio. Credit: Douglas Levere / University at Buffalo / CERN

    Funding comes as the field marks its latest big discovery — the observation of the Higgs boson’s most common mode of decay.

    University at Buffalo scientists have received $1.45 million from the National Science Foundation (NSF) for research in high-energy physics, a field that uses particle accelerators to smash beams of protons into one another at near-light speeds, generating data that illuminates the fundamental laws of nature.

    The grant was awarded to Salvatore Rappoccio, PhD, associate professor of physics in the UB College of Arts and Sciences, and UB physics professors Ia Iashvili, PhD, and Avto Kharchilava, PhD.

    The funding began Sept. 1, just days after the latest big discovery in high-energy physics.

    On Aug. 28, an international team of thousands of researchers — including Iashvili, Kharchilava and Rappoccio — announced that they had observed the Higgs boson, a subatomic particle, decaying into a pair of lighter particles called a bottom quark and antibottom quark.

    The sighting took place at the world’s most powerful particle accelerator, the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN).


    CERN map

    CERN LHC Tunnel

    CERN LHC particles

    The finding deepens our understanding of why objects have mass. It also validates the Standard Model, a set of equations that physicists use to describe elementary particles and the way they behave (in essence, the way the universe works).

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Standard Model of Particle Physics from Symmetry Magazine

    For Kharchilava, the discovery was over a decade in the making. He and his UB students had been searching for evidence of the Higgs boson transforming into bottom quarks since around 2005.

    “I was looking for this decay for almost 15 years, when we began the search at Fermilab, which operated the Tevatron collider,” he says. “We did not succeed back then because we did not have enough data and precision, so now we have more data and better precision and we have finally made the discovery.”

    FNAL/Tevatron map

    FNAL/Tevatron CDF detector

    FNAL/Tevatron DZero detector

    The new NSF funding will enable the UB scientists to continue their work on the Higgs boson, the Standard Model and the hunt for new phenomena in physics.

    The finding deepens our understanding of why objects have mass. It also validates the Standard Model, a set of equations that physicists use to describe elementary particles and the way they behave (in essence, the way the universe works).

    For Kharchilava, the discovery was over a decade in the making. He and his UB students had been searching for evidence of the Higgs boson transforming into bottom quarks since around 2005.

    “I was looking for this decay for almost 15 years, when we began the search at Fermilab, which operated the Tevatron collider,” he says. “We did not succeed back then because we did not have enough data and precision, so now we have more data and better precision and we have finally made the discovery.”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    U Buffalo Campus

    UB is a premier, research-intensive public university and a member of the Association of American Universities. As the largest, most comprehensive institution in the 64-campus State University of New York system, our research, creative activity and people positively impact the world.

  • richardmitnick 9:54 am on February 12, 2018 Permalink | Reply
    Tags: , , , First high-precision measurement of the mass of the W boson at the LHC, FNAL Tevatron, , , ,   

    From CERN ATLAS : “First high-precision measurement of the mass of the W boson at the LHC” 

    CERN ATLAS Higgs Event


    12th February 2018

    Display of a candidate event for a W boson decaying into one muon and one neutrino from proton-proton collisions recorded by ATLAS with LHC stable beams at a collision energy of 7 TeV. (Image: ATLAS Collaboration/CERN).

    In a paper published today in the European Physical Journal C, the ATLAS Collaboration reports the first high-precision measurement at the Large Hadron Collider (LHC) of the mass of the W boson. This is one of two elementary particles that mediate the weak interaction – one of the forces that govern the behaviour of matter in our universe. The reported result gives a value of 80370±19 MeV for the W mass, which is consistent with the expectation from the Standard Model of Particle Physics, the theory that describes known particles and their interactions.

    The measurement is based on around 14 million W bosons recorded in a single year (2011), when the LHC was running at the energy of 7 TeV. It matches previous measurements obtained at Large Electron-Positron Collider[LEP] , the ancestor of the LHC at CERN, and at the Tevatron , a former accelerator at Fermilab [FNAL] in the United States, whose data made it possible to continuously refine this measurement over the last 20 years.


    FNAL Tevatron


    The W boson is one of the heaviest known particles in the universe. Its discovery in 1983 crowned the success of CERN’s Super Proton Synchrotron , leading to the Nobel Prize in physics in 1984. Although the properties of the W boson have been studied for more than 30 years, measuring its mass to high precision remains a major challenge.

    Super Proton Synchrotron

    “Achieving such a precise measurement despite the demanding conditions present in a hadron collider such as the LHC is a great challenge,” said the physics coordinator of the ATLAS Collaboration, Tancredi Carli. “Reaching similar precision, as previously obtained at other colliders, with only one year of Run 1 data is remarkable. It is an extremely promising indication of our ability to improve our knowledge of the Standard Model and look for signs of new physics through highly accurate measurements.”

    The Standard Model is very powerful in predicting the behaviour and certain characteristics of the elementary particles and makes it possible to deduce certain parameters from other well-known quantities. The masses of the W boson, the top quark and the Higgs boson for example, are linked by quantum physics relations. It is therefore very important to improve the precision of the W boson mass measurements to better understand the Higgs boson, refine the Standard Model and test its overall consistency.

    Remarkably, the mass of the W boson can be predicted today with a precision exceeding that of direct measurements. This is why it is a key ingredient in the search for new physics, as any deviation of the measured mass from the prediction could reveal new phenomena conflicting with the Standard Model.

    The measurement relies on a thorough calibration of the detector and of the theoretical modelling of the W boson production. These were achieved through the study of Z boson events and several other ancillary measurements. The complexity of the analysis meant it took almost five years for the ATLAS team to achieve this new result. Further analysis with the huge sample of now-available LHC data, will allow even greater accuracy in the near future.

    See the full article here .

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

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    Quantum Diaries

  • richardmitnick 4:30 pm on December 19, 2017 Permalink | Reply
    Tags: , , , , FNAL Tevatron, , , Large Electron-Positron Collider, , , , , ,   

    From Symmetry: “Machine evolution” 

    Symmetry Mag

    Amanda Solliday

    Courtesy of SLAC

    Planning the next big science machine requires consideration of both the current landscape and the distant future.

    Around the world, there’s an ecosystem of large particle accelerators where physicists gather to study the most intricate details of matter.

    These accelerators are engineering marvels. From planning to construction to operation to retirement, their lifespans stretch across decades.

    But to get the most out of their investments of talent and funding, laboratories planning such huge projects have to think even longer-term: What could these projects become in their next lives?

    The following examples show how some of the world’s big physics machines have evolved to stay at the forefront of science and technology.

    Same tunnel, new collisions

    Before CERN research center in Geneva, Switzerland, had its Large Hadron Collider, it had the Large Electron-Positron Collider. LEP was the largest electron-positron collider ever built, occupying a nearly 17-mile circular tunnel dug beneath the border of Switzerland and France. The tunnel took three years to completely excavate and build.

    The first particle beam traveled around the LEP circular collider in 1989. Long before then, the international group of CERN physicists and engineers were already thinking about what CERN’s next machine could be.

    “People were saying, ‘Well, if we do build LEP, then we should make it compatible with the [then-proposed] Large Hadron Collider,’” says James Gillies, a senior communications advisor and member of the strategic planning and evaluation unit at CERN. “If you want to have a future facility, you often have to engage the people who just finished designing one machine to start thinking about the next one.”

    LEP’s designers chose an energy for the collider that would mass-produce Z bosons, fundamental particles discovered by earlier experiments at CERN. The LHC would be a step up from LEP, reaching higher energies that scientists hoped could produce the Higgs boson. In the 1960s, theorists proposed the Higgs as a way to explain the origin of the mass of elementary particles. And the new machine to look for it could be built in the same 17-mile tunnel excavated for LEP.

    Engineers began working on the LHC while LEP was still running. The new machine required enlargements to underground areas—it needed bigger detectors and new experimental halls.

    “That was challenging because these caverns are huge. As they were being excavated, the pressure on the LEP tunnel was reduced and the LEP beamline needed realignment,” Gillies says. “So you constantly had to realign the collider for experiments as you were digging.”

    After LEP reached its highest energy in 2000, it was switched off. The tunnel remained the same, says Gillies, but there were many other changes. Only one of the LEP detectors, DELPHI, remains underground at CERN as a visitors’ point.

    In 2012, LHC scientists announced the discovery of the long-sought Higgs boson. The LHC is planned to continue running until at least 2035, gradually increasing the intensity of its particle collisions. The research and development into the accelerator’s successor is already happening. The possibilities include a higher energy LHC, a compact linear collider or an even larger circular collider.


    Large Electron-Positron Collider
    Location: CERN—Geneva, Switzerland
    First beam: 1989
    Link to LEP Timeline: Timeline
    Courtesy of CERN


    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    Large Hadron Collider
    Location: CERN—Geneva, Switzerland
    First beam: 2008
    Link to LHC Timeline: Timeline
    Courtesy of CERN

    High-powered science
    Decades before the LHC came into existence, a suburb of Chicago was home to the most powerful collider in the world: the Tevatron. A series of accelerators at Fermi National Accelerator Laboratory boosted protons and antiprotons to nearly the speed of light. In the final, 4-mile Tevatron ring, the particles reached record energy levels, and more than 1000 superconducting magnets steered them into collisions. Physicists used the Tevatron to make the first direct measurement of the tau neutrino and to discover the top quark, the last observed lepton and quark, respectively, in the Standard Model.

    The Tevatron shut down in 2011 after the LHC came up to speed, but the rest of Fermilab’s accelerator infrastructure was still hard at work powering research in particle physics—particularly on the abundant, mysterious and difficult-to-detect neutrino.

    Starting in 1999, a brand-new, 2-mile circular accelerator called the Main Injector was added to the Fermilab complex to increase the number of Tevatron particle collisions tenfold. It was joined in its tunnel by the Recycler, a permanent magnet ring that stored and cooled antiprotons.

    But before the Main Injector was even completed, scientists had identified a second purpose: producing powerful beams of neutrinos for experiments in Illinois and 500 miles away in Minnesota.

    FNAL/NOvA experiment map

    By 2005, the proton beam circulating in the Main Injector was doing double duty: sending ever-more-intense beams to the Tevatron collider and smashing into a target to produce neutrinos. Following the shutdown of the Tevatron, the Recycler itself was recycled to increase the proton beam power for neutrino research.

    “I’m still amazed at how we are able to use the Recycler. It can be difficult to transition if a machine wasn’t originally built for that purpose,” says Ioanis Kourbanis, the head of the Main Injector department at Fermilab.

    Fermilab’s high-energy neutrino beam is already the most intense in the world, but the laboratory plans to enhance it with future improvements to the Main Injector and the Recycler, and to build a brand-new neutrino beamline.

    Neutrinos almost never interact with matter, so they can pass straight through the Earth on their way to detectors onsite and others several hundred miles away. Scientists hope to learn more about neutrinos and their possible role in shaping our early universe.

    The new beamline will be part of the Long-Baseline Neutrino Facility, which will send neutrinos 800 miles underground to the massive, mile-deep detectors of the Deep Underground Neutrino Experiment.

    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

    FNAL DUNE Argon tank at SURF

    Surf-Dune/LBNF Caverns at Sanford

    SURF building in Lead SD USA

    Scientists from around the world will use the DUNE data to answer questions about neutrinos, thanks to the repurposed pieces of the Fermilab accelerator complex.


    FNAL Tevatron

    FNAL/Tevatron map

    FNAL/Tevatron DZero detector

    FNAL/Tevatron CDF detector

    Location: Fermilab—Batavia, Illinois
    First beam: 1983
    Link to Tevatron Timeline: Timeline
    Courtesy of Fermilab


    Neutrinos at the Main Injector (NuMI) beam
    Location: Fermilab—Batavia, Illinois
    First beam: 2004
    Link to Fermilab Timeline: Timeline
    Courtesy of Fermilab

    A monster accelerator

    When physicists first came up with the idea to build a two-mile linear accelerator at what is now called SLAC National Accelerator Laboratory, managed by Stanford University, they called it “Project M” for “Monster.” Engineers began building it from hand-drawn designs. Once completed, the machine was able to accelerate electrons to near the speed of light, producing its first particle beam in May 1966.

    SLAC Campus

    The accelerator’s scientific purpose has gone through several iterations of particle physics experiments over the decades, from fixed-target experiments to the Stanford Linear Collider (the only electron-positron linear collider ever built) to an injector for a circular collider, the Positron-Electron Project.

    These experiments led to the discovery that protons are made of quarks, the first evidence that the charm quark existed (through observations of the J/psi particle, co-discovered with researchers at MIT) and the discovery of the tau lepton.

    In 2009, the lab used the accelerator as the backbone for a different type of science machine—an X-ray free-electron laser, the Linac Coherent Light Source.

    “Looking around, SLAC was the only place in the world with a linear accelerator capable of driving a free-electron laser,” says Claudio Pellegrini, a distinguished professor emeritus of physics at the University of California, Los Angeles and a visiting scientist and consulting professor at SLAC. Pellegrini first proposed the idea to transform SLAC’s linear accelerator.

    The new machine, a DOE Office of Science user facility, would be the world’s first laser of its kind that could produce extremely bright hard X-rays, the high-energy X-rays that let scientists take snapshots of atoms and molecules.

    “Much of the physics and many of the tools learned and developed during the operation of the Stanford Linear Collider were directly applicable to the free electron laser,” says Lia Merminga, head of the accelerator directorate at SLAC. “This was a big factor in the LCLS being commissioned in record time. Without the Stanford Linear Collider experience, this significant body of work would have to be reinvented and reproduced almost from scratch.”

    Little about the accelerator itself needed to change. But to create a free-electron laser, scientists needed to design a new part: an electron gun, a device that generates electrons to be injected into the accelerator. A collaboration of several national labs and UCLA created a new type of electron gun for LCLS, while other national labs helped build undulators, a series of magnets that would wiggle the electrons to create X-rays.

    LCLS used only the last third of SLAC’s original linear accelerator. In part of the remaining section, scientists are developing plasma wakefield and other new particle acceleration techniques.

    For the X-ray laser’s next iteration, LCLS-II, scientists are aiming for an even brighter laser that will fire 1 million pulses per second, allowing them to observe rare and exceptionally transient events.


    To do this, they will need to replace the original copper structures with superconducting technology. The technology is derived from designs for a large International Linear Collider [ILC] proposed to be built in Japan.

    ILC schematic

    “I’m in awe of the foresight of the original builders of SLAC’s linear accelerator,” Merminga adds. “We’ve been able to do so much with this machine, and the end is not yet in sight.”


    Fixed target and collider experiments

    Location: SLAC—Menlo Park, California
    First beam: 1966
    Link to SLAC Timeline: Timeline
    Courtesy of SLAC


    Linac Coherent Light Source
    Location: SLAC—Menlo Park, California
    First beam: 2009
    Link to SLAC Timeline: Timeline
    Courtesy of SLAC

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 10:22 am on October 24, 2017 Permalink | Reply
    Tags: A new chapter in Fermilab’s electron lens legacy, , , , , FNAL Tevatron, Scientists at Fermilab invented and developed one novel collider component 20 years ago: the electron lens   

    From FNAL: “A new chapter in Fermilab’s electron lens legacy” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    October 18, 2017
    Leah Poffenberger

    Sending bunches of protons speeding around a circular particle collider to meet at one specific point is no easy feat. Many different collider components work keep proton beams on course — and to keep them from becoming unruly.

    Scientists at Fermilab invented and developed one novel collider component 20 years ago: the electron lens. Electron lenses are beams of electrons formed into specific shapes that modify the motion of other particles — usually protons — that pass through them.

    The now retired Tevatron, a circular collider at Fermilab, and the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory have both benefited from electron lenses, a concept originally developed at Fermilab.

    FNAL Tevatron

    FNAL/Tevatron map

    FNAL/Tevatron DZero detector

    FNAL/Tevatron CDF detector

    BNL RHIC Campus

    BNL/RHIC Star Detector


    “Electron lenses are like a Swiss Army knife for accelerators: They’re relatively simple and inexpensive, but they can be applied in a wide variety of ways,” said Alexander Valishev, a Fermilab scientist who co-authored a recent study for a new electron lens application, which could be crucial to forthcoming colliders.

    The innovation is detailed in an article published on Sept. 27 in Physical Review Letters. (The article was also recently selected for presentation in the Physics Central’s Physics Buzz Blog.)

    “This little breakthrough in the physics of beams and accelerators is kind of a beginning of a bigger invention — it’s a new thing,” said Fermilab’s Vladimir Shiltsev, an author of the published paper. Shiltsev also played a major role in the origination of electron lenses in 1997. “Fermilab is known for inventions and developments that are, first, exciting, and then, functional. That’s what national labs are built for, and that’s what we’ve achieved.”

    An electron lens introduces differences in the movement of particles that constitute a particle bunch. In the illustration, the perspective is looking down the beam pipe — down the path of the particle bunch. The bunch is seen as approaching the viewer (as the circle increases in size). Left: the particle bunch, represented as a uniformly blue circle, contains particles that all behave in the same way. Because the constituent particles follow the exact same trajectory, the bunch is more susceptible to wild deviations from its path, resulting from electromagnetic wake-fields. Right: Treated by an electron lens, the particle bunch, represented by red and blue, contains particles that move slightly differently from one another. For example, particles closer to the interior of the bunch move differently from those closer to the outside. This variegation helps confine the particle bunch to the more desirable straightforward path. Illustration: Diana Brandonisio

    A lens into the future

    This new type of electron lens, called the Landau damping lens, will be a critical part of a huge, prospective project in particle physics research: the Future Circular Collider at CERN.

    CERN Future Circular Collider

    The FCC would push the boundaries of traditional collider design to further study the particle physics beyond the Higgs boson, a fundamental particle discovered only five years ago.

    The proposed FCC has to be a high-luminosity machine: Its particle beams will need to be compact and densely packed. Compared with CERN’s Large Hadron Collider, the beams will also have a dramatic increase in energy — 50 trillion electronvolts, compared with the LHC’s beam energy of 7 trillion electronvolts. That involves an equally dramatic increase in the size of the accelerator. With a planned circumference of 100 kilometers, the FCC would dwarf the 27-kilometer LHC.


    CERN/LHC Map

    CERN LHC Tunnel

    CERN LHC particles

    These high-energy, high-luminosity supercolliders all experience a problem, regardless of size: An intense beam of protons packed into the width of human hair traveling over a long distance can become unstable, especially if all the protons travel in exactly the same way.

    In a collider, particles arrive in packets called bunches — roughly foot-long streams packed with hundreds of billions of particles. A particle beam is formed of dozens, hundreds or thousands of these bunches.

    Imagine a circular collider as a narrow racetrack, with protons in a bunch as a tight pack of racecars. A piece of debris suddenly appears in the middle of the track, disrupting the flow of traffic. If every car reacts in the same way, say, by veering sharply to the left, it could lead to a major pileup.

    Inside the collider, it’s not a matter of avoiding just one bump on the track, but adjusting to numerous dynamic obstacles, causing the protons to change their course many times over. If an anomaly, such as a kink in the collider’s magnetic field, occurs unexpectedly, and if the protons in the beam all react to it in the same way at the same time, even a slight change of course could quickly go berserk.

    One could avoid the problem by thinning the particle beam from the get-go. By using lower-density proton beams, you provide less opportunity for protons to go off course. But that would mean removing protons and so missing out on potential for scientific discovery.

    Another, better way to address the problem is to introduce differences into the beam so that not all the protons in the bunches behave the same way.

    To return to the racetrack: If the drivers all react to the piece of debris different ways —some moving slightly to the right, others slightly to the left, one brave driver just skips over the top — the cars can all merge back together and continue the race, no accidents.

    Creating differentiations within a proton bunch would do essentially the same thing. Each proton follows its own, ever-so-slightly different course around the collider. This way, any departure from the course is isolated, rather than compounded by protons all misbehaving in concert, minimizing harmful beam oscillations.

    “Particles at the center of the bunch will move differently than particles around the outside,” Shiltsev said. “The protons will all be kind of messed up, but that’s what we want. If they all move together, they become unstable.”

    These differences are usually created with a special type of magnet called octupoles. The Tevatron, before its decommissioning in 2011, had 35 octupole magnets, and the LHC now has 336.

    But as colliders get larger and achieve greater energies, they need exponentially higher numbers of magnets: The FCC will require more than 10,000 octupole magnets, each a meter long, to achieve the same beam-stabilizing results as previous colliders.

    That many magnets take up a lot of space: as much as 10 of the FCC’s 100 kilometers.

    “That seems ridiculous,” Shiltsev said. “We’re looking for a way to avoid that.”

    The scientific community recognizes the Landau damping nonlinear lens as a likely solution to this problem: A single one-meter-long electron lens could replace all 10,000 octupole magnets and possibly do a better job keeping beams stable as they speed toward collision, without introducing any new problems.

    “At CERN they’ve embraced the idea of this new electron lens type, and people there will be studying them in further detail for the FCC,” Valishev said. “Given what we know so far about the issues that the future colliders will face, this would be a device of extremely high criticality. This is why we’re excited.”

    Electron Legos

    The Landau damping lens will join two other electron lens types in the repertoire of tools physicists have to modify or control beams inside a collider.

    “After many years of use, people are very happy with electron lenses: It’s one of the instruments used for modern accelerators, like magnets or superconducting cavities,” Shiltsev said. “Electron lenses are just one of the building blocks or Lego pieces.”

    Electron lenses are a lot like Legos: Lego pieces are made of the same material and can be the same color, but a different shape determines how they can be used. Electron lenses are all made of clouds of electrons, shaped by magnetic fields. The shape of the lens dictates how the lens influences a beam of protons.

    Scientists developed the first electron lens at Fermilab in 1997 for use to compensate for so-called beam-beam effects in the Tevatron, and a similar type of electron lens is still in use at the Brookhaven’s RHIC.

    In circular colliders, particle beams pass by each other, going in opposing directions inside the collider until they are steered into a collision at specific points. As the beams buzz by one another, they exert a small force on each other, which causes the proton bunches to expand slightly, decreasing their luminosity.

    That first electron lens, called the beam-beam compensation lens, was created to combat the interaction between the beams by squeezing them back to their original, compact state.

    After the success of this electron lens type in the Tevatron, scientists realized that electron beams could be shaped a second way to create another type of electron lens.

    Scientists designed the second lens to be shaped like a straw, allowing the proton beam to pass through the inside unaffected. The occasional proton might try to leave its group and stray from the center of the beam. In the LHC, losing even one-thousandth of the total number of protons in an uncontrolled way could be dangerous. The electron lens acts as a scraper, removing these rogue particles before they could damage the collider.

    “It’s extremely important to have the ability to scrape these particles because their energy is enormous,” Shiltsev said. “Uncontrolled, they can drill holes, break magnets or produce radiation.”

    Both types of electron lens have made their mark in collider design as part of the success of the Tevatron, RHIC and the LHC. The new Landau damping lens may help usher in the next generation of colliders.

    “The electron lens is an example of something that was invented here at Fermilab 20 years ago,” Shiltsev said. “This is a one of the rare technologies that wasn’t just brought to perfection at Fermilab: It was invented, developed and perfected and still continues to shine.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    FNAL Icon
    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

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