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  • richardmitnick 10:22 am on October 24, 2017 Permalink | Reply
    Tags: A new chapter in Fermilab’s electron lens legacy, BNL/RHIC, , , , , 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

    BNL RHIC PHENIX

    “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.”

    1
    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.

    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.

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    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.

     
  • richardmitnick 11:35 am on August 4, 2017 Permalink | Reply
    Tags: 'Perfect Liquid' Quark-Gluon Plasma is the Most Vortical Fluid, , , BNL/RHIC, New record for "vorticity", , , STAR detector's Time Project Chamber   

    From BNL: “‘Perfect Liquid’ Quark-Gluon Plasma is the Most Vortical Fluid” 

    Brookhaven Lab

    August 2, 2017
    Karen McNulty Walsh
    kmcnulty@bnl.gov
    (631) 344-8350

    Peter Genzer,
    genzer@bnl.gov
    (631) 344-3174

    Swirling soup of matter’s fundamental building blocks spins ten billion trillion times faster than the most powerful tornado, setting new record for “vorticity”.

    1
    Ohio State University graduate student Isaac Upsal helped lead the analysis of results from the STAR detector that revealed a “vorticity” record for the quark-gluon plasma created in collisions at the Relativistic Heavy Ion Collider (RHIC).

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    Particle collisions recreating the quark-gluon plasma (QGP) that filled the early universe reveal that droplets of this primordial soup swirl far faster than any other fluid. The new analysis of data from the Relativistic Heavy Ion Collider (RHIC) — a U.S. Department of Energy Office of Science User Facility for nuclear physics research at Brookhaven National Laboratory — shows that the “vorticity” of the QGP surpasses the whirling fluid dynamics of super-cell tornado cores and Jupiter’s Great Red Spot by many orders of magnitude, and even beats out the fastest spin record held by nanodroplets of superfluid helium.

    The results, just published in Nature, add a new record to the list of remarkable properties ascribed to the quark-gluon plasma. This soup made of matter’s fundamental building blocks — quarks and gluons — has a temperature hundreds of thousands of times hotter than the center of the sun and an ultralow viscosity, or resistance to flow, leading physicists to describe it as “nearly perfect.” By studying these properties and the factors that control them, scientists hope to unlock the secrets of the strongest and most poorly understood force in nature — the one responsible for binding quarks and gluons into the protons and neutrons that form most of the visible matter in the universe today.

    Specifically, the results on vorticity, or swirling fluid motion, will help scientists sort among different theoretical descriptions of the plasma. And with more data, it may give them a way to measure the strength of the plasma’s magnetic field — an essential variable for exploring other interesting physics phenomena.

    “Up until now, the big story in characterizing the QGP is that it’s a hot fluid that expands explosively and flows easily,” said Michael Lisa, a physicist from Ohio State University (OSU) and a member of RHIC’s STAR collaboration. “But we want to understand this fluid at a much finer level. Does it thermalize, or reach equilibrium, quickly enough to form vortices in the fluid itself? And if so, how does the fluid respond to the extreme vorticity?” The new analysis, which was led by Lisa and OSU graduate student Isaac Upsal, gives STAR a way to get at those finer details.

    3
    Telltale signs of a lambda hyperon (Λ) decaying into a proton (p) and a pion (π-) as tracked by the Time Projection Chamber of the STAR detector. Because the proton comes out nearly aligned with the hyperon’s spin direction, tracking where these “daughter” protons strike the detector can be a stand-in for tracking how the hyperons’ spins are aligned.

    Aligning spins

    “The theory is that if I have a fluid with vorticity — a whirling substructure — it tends to align the spins of the particles it emits in the same direction as the whirls,” Lisa said. And, while there can be many small whirlpools within the QGP all pointing in random directions, on average their spins should align with what’s known as the angular momentum of the system — a rotation of the system generated by the colliding particles as they speed past one another at nearly the speed of light.

    To track the spinning particles and the angular momentum, STAR physicists correlated simultaneous measurements at two different detector components. The first, known as the Beam-Beam Counters, sit at the front and rear ends of the house-size STAR detector, catching subtle deflections in the paths of colliding particles as they pass by one another. The size and direction of the deflection tells the physicists how much angular momentum there is and which way it is pointing for each collision event.

    Meanwhile, STAR’s Time Project Chamber, a gas-filled chamber that surrounds the collision zone, tracks the paths of hundreds or even thousands of particles that come out perpendicular to the center of the collisions.

    “We’re specifically looking for signs of Lambda hyperons, spinning particles that decay into a proton and a pion that we measure in the Time Projection Chamber,” said Ernst Sichtermann, a deputy STAR spokesperson and senior scientist at DOE’s Lawrence Berkeley National Laboratory. Because the proton comes out nearly aligned with the hyperon’s spin direction, tracking where these “daughter” protons strike the detector can be a stand-in for tracking how the hyperons’ spins are aligned.

    “We are looking for some systematic preference for the direction of these daughter protons aligned with the angular momentum we measure in the Beam-Beam Counters,” Upsal said. “The magnitude of that preference tells us the degree of vorticity — the average rate of swirling — of the QGP.”

    4
    Tracking particle spins reveals that the quark-gluon plasma created at the Relativistic Heavy Ion Collider is more swirly than the cores of super-cell tornados, Jupiter’s Great Red Spot, or any other fluid!

    Super spin

    The results reveal that RHIC collisions create the most vortical fluid ever, a QGP spinning faster than a speeding tornado, more powerful than the fastest spinning fluid on record. “So the most ideal fluid with the smallest viscosity also has the most vorticity,” Lisa said.

    This kind of makes sense, because low viscosity in the QGP allows the vorticity to persist, Lisa said. “Viscosity destroys whirls. With QGP, if you set it spinning, it tends to keep on spinning.”

    The data are also in the ballpark of what different theories predicted for QGP vorticity. “Different theories predict different amounts, depending on what parameters they include, so our results will help us sort through those theories and determine which factors are most relevant,” said Sergei Voloshin, a STAR collaborator from Wayne State University. “But most of the theoretical predications were too low,” he added. “Our measurements show that the QGP is even more vortical than predicted.”

    This discovery was made during the Beam Energy Scan program, which exploits RHIC’s unique ability to systematically vary the energy of collisions over a range in which other particularly interesting phenomena have been observed. In fact, theories suggest that this may be the optimal range for the discovery and subsequent study of the vorticity-induced spin alignment, since the effect is expected to diminish at higher energy.

    Increasing the numbers of Lambda hyperons tracked in future collisions at RHIC will improve the STAR scientists’ ability to use these measurements to calculate the strength of the magnetic field generated in RHIC collisions. The strength of magnetism influences the movement of charged particles as they are created and emerge from RHIC collisions, so measuring its strength is important to fully characterize the QGP, including how it separates differently charged particles.

    “Theory predicts that the magnetic field created in heavy ion experiments is much higher than any other magnetic field in the universe,” Lisa said. At the very least, being able to measure it accurately may nab another record for QGP.

    Research at RHIC and with the STAR detector is funded primarily by the DOE Office of Science.

    See the full article here .

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 9:17 pm on July 19, 2017 Permalink | Reply
    Tags: , BNL/RHIC, Helen Caines, , ,   

    From Yale: Women in STEM -“Yale’s Helen Caines takes a leadership role in international STAR experiment” 

    Yale University bloc

    Yale University

    July 12, 2017

    Jim Shelton
    james.shelton@yale.edu
    203-361-8332

    1
    The left half of this image shows the Solenoidal Tracker at RHIC. It is a detector that specializes in tracking the thousands of particles produced by each ion collision at RHIC. The right half of the image shows the end view of a collision of two 30-billion electron-volt gold beams in the STAR detector at RHIC. (Image courtesy of STAR)

    BNL RHIC Campus

    BNL/RHIC Star Detector

    BNL RHIC PHENIX

    Helen Caines has spent much of her professional life immersed in cosmic soup.

    While other physicists have chased gravitational waves, cultivated qubits, and mused about dark matter, Caines has focused squarely on the thick glop of particles that transformed into nuclear matter in the first milliseconds after the Big Bang. Through studying these particles, Caines believes, humanity can come to understand the basic processes that formed the early universe at that instant.

    Now Caines is a leading voice in explaining how much we’ve learned so far and what is to come. On July 1, she became co-spokesperson for the STAR experiment, an international collaboration of more than 600 physicists searching for the theorized “critical point” that transformed the universe from a soup of quarks into what we know as matter today.

    “We’re doing very exciting physics, things we never dreamed we’d be able to do when we started,” said Caines, an associate professor of physics and member of Yale’s Wright Lab. “STAR is a testament to how innovative a collaboration can be. We have the whole range of experience, from undergraduates to emeritus professors working with us.”

    The STAR experiment is focused on the dense, hot soup of quarks and gluons — known as the quark-gluon plasma — that is believed to have existed ten millionths of a second after the Big Bang. These conditions can be recreated in the laboratory by colliding heavy ions and studying the reactions — an endeavor that still amazes Caines even after more than 20 years of research.

    “It’s just so intriguing that you can smash heavy ions together and actually learn something about the early universe from it,” she said. “It’s like smashing two automobiles together and then trying to determine the make and model of each one.”

    2
    Helen Caines will co-lead the STAR experiment’s investigation of what happened ten millionths of a second after the Big Bang. (Photo by Michael Marsland)

    STAR launched in 1991 and is based at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory.


    The experiment began collecting data in 2000. More than 60 institutions in 13 countries are part of STAR.

    Yale’s involvement in the STAR experiment runs deep. Zhangbu Xu, co-spokesperson with Caines, has a Yale Ph.D., and Yale physics professor John Harris was the founding spokesperson, serving from 1991 until 2002. Current Yale collaborators, along with Caines and Harris, are emeritus professor Jack Sandweiss; adjunct professor Thomas Ullrich; graduate students Stephen Horvat, Daniel Nemes, and David Stewart; senior research scientist Richard Majka; research scientist Nikolai Smirnov; and postdoctoral associates Saehanseul Oh and Li Yi.

    “Yale has been committed to heavy ion physics research since the founding by professor D. Allan Bromley of the original Wright Nuclear Structure Laboratory in 1966 and its various upgrades of its tandem van de Graaff accelerators,” Harris said. Yale became a member institution of the STAR experiment in 1996, when Harris arrived on campus.

    Caines joined the experiment in 1996 as well. Her work involves measuring the high-momentum particles that are produced when ultra-relativistic heavy ions are collided. Specifically, she focuses on the particles’ movement through the surrounding soup. The work is helping scientists start to understand the properties and characteristics of a new state of matter in transition.

    This is where the so-called “critical point” becomes essential to physicists. Caines has been a major proponent for a program at RHIC called Beam Energy Scan, which has successfully concluded its first phase of experiments and is in the middle of its analysis.

    “BES covers the full range of collision energies at RHIC with the primary goal of potentially discovering a critical point that is predicted to exist in the phase diagram of nuclear matter,” Harris said. “At this critical point nuclear matter transforms into a plasma of quarks and gluons in a first order phase transition, where nuclear particles as we know them coexist for an instant with quarks and gluons in a very hot phase, about 100,000 times hotter than our Sun.”

    Caines will co-lead STAR in its continuing investigation of this nuclear phase and help lead a second phase of experiments over the next few years. She and Yale graduate student Horvat have identified an approximate region in collision energy and temperature where researchers may find the critical point — a region where the hotter phase of quarks and gluons gives way to the cooler nuclear phase.

    Caines’ colleagues say she is well suited to her new role.

    “These large collaborations require a lot from a spokesperson,” said Sarah Demers, the Horace Taft Associate Professor of Physics at Yale and a member of the ATLAS experiment at CERN’s Large Hadron Collider in Geneva, Switzerland. “You need to be a physics detector expert, a physics analysis expert, and you need to be able to keep your colleagues inspired and behind a common plan. Helen is an excellent physicist, and she knows how to lead a team.”

    Caines received her Ph.D. from the University of Birmingham, U.K., in 1996. She was appointed assistant professor at Yale in 2004 and promoted to associate professor in 2010. She is a faculty member of Yale’s Wright Lab.

    Part of the satisfaction of her job, she said, is the opportunity to be surprised even after decades of research. The STAR experiment exemplifies this, she explained.

    “We’re at a very interesting stage,” Caines said. “We think we may find a place in nuclear matter, where things go wild.”

    See the full article here .

    Please help promote STEM in your local schools.

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    Yale University comprises three major academic components: Yale College (the undergraduate program), the Graduate School of Arts and Sciences, and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

     
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