From Fermi National Accelerator Lab: “Discovery of a new type of particle beam instability”

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From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

November 14, 2019
Alexey Burov

Accelerated, charged particle beams do what light does for microscopes: illuminate matter. The more intense the beams, the more easily scientists can examine the object they are looking at. But intensity comes with a cost: the more intense the beams, the more they become prone to instabilities.

One type of instability occurs when the average energy of accelerated particles traveling through a circular machine reaches its transition value. The transition point occurs when the particles revolve around the ring at the same rate, even though they do not all carry the same energy — in fact, they exhibit a range of energies. The specific motion of the particles near the transition energy makes them extremely prone to collective instabilities.

These particular instabilities were observed for decades, but they were not sufficiently understood. In fact, they were misinterpreted. In a paper published this year, I suggest a new theory about these instabilities. The application of this theory to the Fermilab Booster accelerator predicted the main features of the instability there at the transition crossing, suggesting better ways to suppress the instability. Recent measurements confirmed the predictions, and more detailed experimental beam studies are planned in the near future.

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Recent measurements at the Fermilab Booster accelerator confirmed existence of a certain kind of particle beam instability. More measurements are planned for the near future to examine new methods proposed to mitigate it.

Accelerating high-intensity beams is a crucial part of the Fermilab scientific program. A solid theoretical understanding of particle beam behavior equips experimentalists to better manipulate the accelerator parameters to suppress instability. This leads to the high-intensity beams needed for Fermilab’s experiments in fundamental physics. It is also useful for any experiment or institution operating circular accelerators.

Beam protons talk to each other by electromagnetic fields, which are of two kinds. One is called the Coulomb field. These fields are local and, by themselves, cannot drive instabilities. The second kind is the wake field. Wake fields are radiated by the particles and trail behind them, sometimes far behind.

When a particle strays from the beam path, the wake field translates this departure backward — in the wake left by the particle. Even a small departure from the path may not escape being carried backward by these electromagnetic fields. If the beams are intense enough, their wakes can destabilize them.

In the new theory, I suggested a compact mathematical model that effectively takes both sorts of fields into account, realizing that both of them are important when they are strong enough, as they typically are near transition energy.

This kind of huge amplification happens at CERN’s Proton Synchrotron, for example, as I showed in my more recent paper, submitted to Physical Review Accelerators and Beams. If not suppressed one way or another, this amplification may grow until the beam touches the vacuum chamber wall and becomes lost. Recent measurements at the Fermilab Booster confirmed existence of a similar instability there; more measurements are planned for the near future to examine new methods proposed to mitigate it.

These phenomena are called transverse convective instabilities, and the discoveries of how they arise open new doors to theoretical, numerical and experimental ways to better understanding and better dealing with the intense proton beams.

This work is supported by the DOE Office of Science.

Science paper:
Convective instabilities of bunched beams with space charge
Physical Review Accelerators and Beams

See the full here.


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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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From Symmetry: “How do you make the world’s most powerful neutrino beam?”

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From Symmetry<

11/13/19
Lauren Biron

DUNE will need lots of neutrinos—and to make them, scientists and engineers will use extreme versions of some common sounding ingredients: magnets and pencil lead.

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Photo by Reidar Hahn, Fermilab

What do you need to make the most intense beam of neutrinos in the world? Just a few magnets and some pencil lead. But not your usual household stuff. After all, this is the world’s most intense high-energy neutrino beam, so we’re talking about jumbo-sized parts: magnets the size of park benches and ultrapure rods of graphite as tall as Danny DeVito.

Physics experiments that push the extent of human knowledge tend to work at the extremes: the biggest and smallest scales, the highest intensities. All three are true for the international Deep Underground Neutrino Experiment, hosted by the Department of Energy’s Fermilab.

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

The design of the experiment is elegant—produce neutrinos and measure them at Fermilab, send them straight through 1,300 kilometers of earth, then measure them again in giant liquid-argon detectors at Sanford Lab.
Courtesy of Fermilab

The experiment brings together more than 1000 people from 30-plus countries to tackle questions that have kept many a person awake at night: Why is the universe full of matter and not antimatter, or no matter at all? Do protons, one of the building blocks of atoms (and of us), ever decay? How do black holes form? And did I leave the stove on?

Maybe not the last one.

To tackle the biggest questions, DUNE will look at mysterious subatomic particles called neutrinos: neutral, wispy wraiths that rarely interact with matter. Because neutrinos are so antisocial, scientists will build enormous particle detectors to catch and study them. More matter inside the DUNE detectors means more things for neutrinos to interact with, and these behemoth neutrino traps will contain a total of 70,000 tons of liquid argon. At their home 1.5 kilometers below the rock in the Sanford Underground Research Facility in South Dakota, they’ll be shielded from interfering cosmic rays—though neutrinos will have no trouble passing through that buffer and hitting their mark.

SURF-Sanford Underground Research Facility, Lead, South Dakota, USA

The detectors can pick up neutrinos from exploding stars that might evolve into black holes and capture interactions from a deliberately aimed beam of neutrinos.

Neutrinos (and their antimatter counterparts, antineutrinos) are born as other particles decay, carrying away small amounts of energy to balance the cosmic ledger. You’ll find them coming in droves from stars like our sun, inside Earth, even the potassium in bananas. But if you want to make trillions of high-energy neutrinos every second and send them to a particle detector deep underground, you’d be hard-pressed to do it by throwing fruit toward South Dakota.

That’s where Fermilab’s particle accelerator complex comes in.

Fermilab sends particles through a series of accelerators, each adding a burst of speed and energy. Work has started for an upgrade to the complex that will include a new linear accelerator at the start of the journey: PIP-II. This is the first accelerator project in the United States with major international contributions, and it will propel particles to 84% of the speed of light as they travel about the length of two football fields. Particles then enter the booster for another… well, boost, and finally head to the Main Injector, Fermilab’s most powerful accelerator.

FNAL booster

FNAL Main Injector Accelerator

The twist? Fermilab’s particle accelerators propel protons—useful particles, but not the ones that neutrino scientists want to study.

So how do researchers plan to turn Fermilab’s first megawatt beam of protons into the trillions of high-energy neutrinos they need for DUNE every second? This calls for some extra infrastructure: The Long-Baseline Neutrino Facility, or LBNF. A long baseline means that LBNF will send its neutrinos a long distance—1300 kilometers, from Fermilab to Sanford Lab—and the neutrino facility means … let’s make some neutrinos.

Step 1: Grab some protons

The first step is to siphon off particles from the Main Injector—otherwise, the circular accelerator will act more like a merry-go-round. Engineers will need to build and connect a new beamline. That’s no easy feat, considering all the utilities, other beamlines, and Main Injector magnets around.

“It’s in one of the most congested areas of the Fermilab accelerator complex,” says Elaine McCluskey, the LBNF project manager at Fermilab. Site prep work starting at Fermilab in 2019 will move some of the utilities out of the way. Later, when it’s time for the LBNF beamline construction, the accelerator complex will temporarily power down.

Crews will move some of the Main Injector magnets safely out of the way and punch into the accelerator’s enclosure. They’ll construct a new extraction area and beam enclosure, then reinstall the Main Injector magnets with a new Fermilab-built addition: kicker magnets to change the beam’s course. They’ll also build the new LBNF beamline itself, using 24 dipole and 17 quadrupole magnets, most of them built by the Bhabha Atomic Research Centre in India.

Step 2: Aim

Neutrinos are tricky particles. Because they are neutral, they can’t be steered by magnetic forces in the same way that charged particles (such as protons) are. Once a neutrino is born, it keeps heading in whatever direction it was going, like a kid riding the world’s longest Slip ‘N Slide. This property makes neutrinos great cosmic messengers but means an extra step for Earth-bound engineers: aiming.

As they build the LBNF beamline, crews will drape it along the curve of an 18-meter-tall hill. When the protons descend the hill, they’ll be pointed toward the DUNE detectors in South Dakota. Once the neutrinos are born, they’ll continue in that same direction, no tunnel required.

With all the magnets in place and everything sealed up tight, accelerator operators will be able to direct protons down the new beamline, like switching a train on a track. But instead of pulling into a station, the particles will run full speed into a target.

Step 3: Smash things

The target is a crucial piece of engineering. While still being designed, it’s likely to be a 1.5-meter-long rod of pure graphite—think of your pencil lead on steroids.

Together with some other equipment, it will sit inside the target hall, a sealed room filled with gaseous nitrogen. DUNE will start up with a proton beam that will run at more than 1 megawatt of power, and there are already plans to upgrade the beam to 2.4 megawatts. Almost everything being built for LBNF is designed to withstand that higher beam intensity.

Because of the record-breaking beam power, manipulating anything inside the sealed hall will likely require the help of some robot friends controlled from outside the thick walls. Engineers at KEK, the high-energy accelerator research organization in Japan, are working on prototypes for elements of the sealed LBNF target hall design.

KEK-Accelerator Laboratory, Tsukuba, Japan

The high-power beam of protons will enter the target hall and smash into the graphite like bowling balls hitting pins, depositing their energy and unleashing a spray of new particles—mostly pions and kaons.

“These targets have a very hard life,” says Chris Densham, group leader for high-power targets at STFC’s Rutherford Appleton Laboratory in the UK, which is responsible for the design and production of the target for the one-megawatt beam.

STFC Rutherford Appleton Laboratory at Harwell in Oxfordshire

“Each proton pulse causes the temperature to jump up by a few hundred degrees in a few microseconds.”

The LBNF target will operate around 500 degrees Celsius in a sort of Goldilocks scenario. Graphite performs well when it’s hot, but not too hot, so engineers will need to remove excess heat. But they can’t let it get too cool, either. Water, which is used in some current target designs, would provide too much cooling, so specialists at RAL are also developing a new method. The current proposed design circulates gaseous helium, which will be moving about 720 kilometers per hour—the speed of a cruising airliner—by the time it exits the system.

Step 4: Focus the debris

As protons strike the target and produce pions and kaons, devices called focusing horns take over. The pions and kaons are electrically charged, and these giant magnets direct the spray back into a focused beam. A series of three horns that will be designed and built at Fermilab will correct the particle paths and aim them at the detectors at Sanford Lab.

For the design to work, the target—a cylindrical tube—must sit inside the first horn, cantilevered into place from the upstream side. This causes some interesting engineering challenges. It boils down to a balance between what physicists want—a lengthier target that can stay in service for longer—with what engineers can build. The target is only a couple of centimeters in diameter, and every extra centimeter of length makes it more likely to droop under the barrage of protons and the pull of Earth’s gravity.

Much like a game of Operation, physicists don’t want the target to touch the sides of the horn.

To create the focusing field, the metallic horns receive a 300,000-amp electromagnetic pulse about once per second—delivering more charge than a powerful lightning bolt. If you were standing next to it, you’d want to stick your fingers in your ears to block out the noise—and you certainly wouldn’t want anything touching the horns, including graphite. Engineers could support the target from both ends, but that would make the inevitable removal and replacement much more complicated.

“The simpler you can make it, the better,” Densham says. “There’s always a temptation to make something clever and complicated, but we want to make it as dumb as possible, so there’s less to go wrong.”

Step 5: Physics happens

Focused into a beam, the pions and kaons exit the target hall and travel through a 200-meter-long tunnel full of helium. As they do, they decay, giving birth to neutrinos and some particle friends. Researchers can also switch the horns to focus particles with the opposite charge, which will then decay into antineutrinos. Shielding at the end of the tunnel absorbs the extra particles, while the neutrinos or antineutrinos sail on, unperturbed, straight through dirt and rock, toward their South Dakota destiny.

“LBNF is a complex project, with a lot of pieces that have to work together,” says Jonathan Lewis, the LBNF Beamline project manager. “It’s the future of the lab, the future of the field in the United States, and an exciting and challenging project. The prospect of uncovering the properties of neutrinos is exciting science.”

Time to science

DUNE scientists will examine the neutrino beam at Fermilab just after its production using a sophisticated particle detector on site, placed right in the path of the beam. Most neutrinos will pass straight through the detector, like they do with all matter. But a small fraction will collide with atoms inside the DUNE near-site detector, providing valuable information on the composition of the neutrino beam as well as high-energy neutrino interactions with matter.

Then it’s time to wave farewell to the other neutrinos. Be quick—their 1300-kilometer journey at close to the speed of light will take four milliseconds, not even close to how long it takes to blink your eye. But for DUNE scientists, the work will be only beginning.

FNAL Long-Baseline Neutrino Facility – South Dakota Site


DUNE’s far detector will use four modules to capture interactions between argon atoms and the neutrinos sent from the LBNF beamline at Fermilab.

Scientists will measure the neutrinos again with their gigantic particle detectors in South Dakota. Researchers will collect mountains of data, examine how neutrinos change, and try to figure out some of the many neutrino puzzles, including: which of the three types of neutrinos is actually the lightest? Do neutrinos behave the same as their antimatter counterparts? And the biggest question of all, are neutrinos the key to why matter won the battle with antimatter at the dawn of the universe?

They’re lofty topics, and scientists have been preparing for this monumental work. Fermilab has a rich history of neutrino research, including short-distance experiments like MicroBooNE and MINERvA and long-distance projects like NOvA and MINOS.

FNAL/MicrobooNE

Scientists at Fermilab use the MINERvA to make measurements of neutrino interactions that can support the work of other neutrino experiments. Photo Reidar Hahn

NOvA Far Detector Block

FNAL/NOvA experiment map

FNAL/MINOS

DUNE will benefit from the experience gained building and running those experiments, much like LBNF will benefit from the experience of building the NuMI (Neutrinos from the Main Injector) beamline, built to make neutrinos for the MINOS detectors at Fermilab and in Minnesota.

Fermilab NuMI Tunnel

“The NuMI beamline was something we had never made at Fermilab, and it enabled us to learn a lot of things about how to make neutrinos, operate a beamline efficiently, and replace components,” McCluskey says. “We have a lot of people who worked on that beamline who are designing the new one, and incorporating those lessons to make an effective, efficient, and unprecedented beam power for DUNE.”

And that’s how you make the world’s most powerful neutrino beam.

See the full article here .


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Symmetry is a joint Fermilab/SLAC publication.


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From Fermi National Accelerator Lab: “DOE awards Fermilab and partners $3.2 million for Illinois quantum network”

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FNAL Art Image by Angela Gonzales

From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

November 13, 2019
edited by Leah Hesla

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The proposed Illinois Express Quantum Network is a metropolitan-scale, quantum-classical hybrid design combining quantum technologies with existing classical networks to create a multinode system for multiple users.

The Department of Energy has announced that it will grant Fermilab and partner institutions $3.2 million to develop designs for transparent optical quantum networks and demonstrate their operation in the greater Chicago area.

The proposed Illinois-Express Quantum Network, or IEQNET, connects nodes at Fermilab and proposed nodes at Northwestern University’s Chicago and Evanston campuses. The metropolitan-scale network uses a combination of cutting-edge quantum and classical technologies to transmit quantum information and will be designed to coexist with classical networks.

“Our team brings together researchers who are leading the way in quantum communications, classical networking, quantum devices and fast-timing electronics,” said scientist Panagiotis Spentzouris, head of quantum science at Fermilab and the project’s principal investigator. “That marriage of world-class expertise enables us to develop the new network.”

Fermilab is the lead institution for the IEQNET collaboration, which includes the Department of Energy’s Argonne National Laboratory, Caltech and Northwestern University.

“We have leading quantum technology capabilities at our respective institutions,” said Northwestern University’s Prem Kumar, one of the researchers on the project. “Now we’re combining them to create new opportunities for distributed quantum communications.”

Scientists have previously demonstrated point-to-point quantum communications over short distances — on the order of 10 miles — in fiber-optic cables. IEQNET’s goal is to demonstrate a multinode fiber-optic quantum network that supports multiple users.

“We will be using state-of-the-art sources and photodetectors in nodes we have built already at Fermilab to co-distribute classical and quantum information across Chicagoland,” said Caltech scientist Maria Spiropulu, another IEQNET researcher. “We want to identify and address the challenges toward nontrivial, long-distance multilayered architectures that support multiple end-users and test various protocols.”

IEQNET’s objective supports the United States in meeting the goals of its National Quantum Initiative, a coordinated multiagency program to support research and training in quantum information science. It also positions Chicago as one of the few places in the nation advancing quantum communications. The proposed network stretches between the Chicago area institutions using existing fiber-optic cables.

“We want to utilize existing links because we have significant infrastructure that has already been laid for classical communications,” said Rajkumar Kettimuthu, an Argonne scientist affiliated with IEQNET. “One of the challenges will be to achieve classical and quantum co-existence in the same fibers.”

IEQNET leverages existing conventional infrastructure and experience from ESnet, a high-speed computer network serving DOE scientists and their collaborators worldwide. ESnet is managed by Lawrence Berkeley National Laboratory, also a DOE national laboratory.

The project also brings together small quantum tech industry partners, including businesses such as NuCrypt and HyperLight, and the Intelligent Quantum Networks and Technologies, or INQNET, program, which was developed through a Caltech and AT&T partnership and is a member of the Quantum Economic Development Consortium of the National Institute of Standards and Technology.

By connecting business with academia, IEQNET has the potential to generate new technologies that have wider application in industry, helping elevate the Chicago area as a hot spot for technology transfer in quantum science.

IEQNET is one of the recently announced five four-year projects aimed at developing wide-area quantum networks funded by the DOE Office of Science.

“We are on the threshold of a new era in quantum information science and quantum computing and networking, with potentially great promise for science and society,” said DOE Under Secretary for Science Paul Dabbar in an announcement from DOE. “These projects will help ensure U.S. leadership in these important new areas of science and technology.”

See the full here.


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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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From Fermi National Accelerator Lab: “Gotta catch ’em all: new NOvA results with neutrinos and antineutrinos”

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FNAL Art Image by Angela Gonzales

From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

November 7, 2019
Steven Calvez
Erika Catano Mur

The latest results from the Fermilab NOvA experiment are taking us closer to describing the most basic properties of the mysterious neutrino — the most abundant particle of matter in the universe.

Neutrinos appear in a variety of natural processes, from formidable supernova explosions and nuclear reactions in the sun to radioactive decays in your banana. They are also produced in abundance in nuclear reactors and particle accelerators. Yet neutrinos barely interact with matter: a light-year of lead would hardly stop your average neutrino. Their elusive nature makes them extremely challenging to study, which explains both why we still know very little about their properties and why many scientists and experiments around the world have so much fun hunting them down.

The observation that neutrinos are able to change type — a behavior called oscillation — proved that neutrinos have masses, albeit very small. This phenomenon explains how neutrinos that are produced in one of the three “flavor” states (electron neutrino, muon neutrino or tau neutrino) transition in and out of these types as they travel a certain distance and may be detected as a different type. The probability of these transitions depends on a number of factors: the energy of the neutrino, the distance between the particle beam source and the detector, the differences in neutrino masses, the amount of blending between neutrino types, which scientists describe with three “mixing” angles, and additional complex phases.

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Fermilab’s NOvA neutrino experiment studies neutrino oscillations using a powerful neutrino beam produced by the lab’s accelerator complex. The beam, made of muon neutrinos, is sent to NOvA’s two detectors — one located at Fermilab and one located about 800 kilometers away in Minnesota, pictured here.

Fermilab’s NOvA neutrino experiment studies neutrino oscillations using the powerful NuMI neutrino beam produced by the lab’s accelerator complex. The beam, made of muon neutrinos, is sent to NOvA’s two detectors — one located at Fermilab and one located about 800 kilometers away in Minnesota. The NOvA far detector looks to identify the fraction of muon neutrinos in the NuMI beam that oscillated into electron neutrinos (called electron neutrino appearance) and the fraction of muon neutrinos that oscillated to a different flavor (called muon neutrino disappearance).

The NuMI beam is generally described as a muon neutrino beam, but it can also be made of muon antineutrinos. The antineutrino is the antiparticle of the neutrino. Just as muon neutrinos can oscillate into electron neutrinos, muon antineutrinos can oscillate into electron antineutrinos.

Experimentalists can use information from the combination of the measurements of electron and muon neutrinos, as well as their antiparticle equivalents, to draw their conclusions. For example, if the oscillation rates of antineutrinos compared to those of neutrinos are different, the implication could be a violation of a symmetry called charge parity, commonly called CP. The existence of this type of CP violation is one of the great unknowns in particle physics that NOvA is investigating.

NOvA’s latest measurements of neutrino oscillation parameters have been published in Physical Review Letters. The data were recorded between 2014 and 2019 and correspond to 8.85 x 1020 protons-on-target of neutrino beam and 12.33 x 1020 protons-on-target of antineutrino beam. This represents a 78% increase in the amount of antineutrino data compared to NOvA’s previous results, presented at the Neutrino 2018 conference.

NOvA identified 27 electron antineutrino candidate events in the NOvA far detector, compared to the 10.3 events expected if muon antineutrinos did not oscillate into electron antineutrinos. This remains the strongest evidence (4.4 sigma) of electron antineutrino appearance in a muon antineutrino beam for a long-baseline experiment. (In particle physics, 3 sigma is usually considered “strong evidence” that the conclusions of the data analysis are unlikely to be a fluke, while 5 sigma means that the experimental results qualify as a discovery.)

In addition to those 27 electron antineutrino events, 102 surviving muon antineutrino candidates were detected in the far detector, where 476 events would have been expected if muon antineutrinos did not oscillate at all. NOvA scientists combined these new events with previously recorded neutrino data and analyzed them jointly. Pictures of such neutrino and antineutrino events as recorded by the NOvA far detector are shown below.

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Four events observed in the NOvA far detector, classified as muon (left) or electron (right) neutrino interactions, with the beam in neutrino (top) or antineutrino (bottom) mode. Each panel shows two views of the same event, and the color represents the energy deposited by particles that emerged from the interaction. The latest NOvA results comprise four data samples with 113 muon neutrino to muon neutrino, 58 muon neutrino to electron neutrino, 102 muon antineutrino to muon antineutrino and 27 muon antineutrino to electron antineutrino candidates.

The results help scientists chip away another problem in neutrino physics: the ordering of the three neutrino masses — which of the three is the lightest? NOvA’s combined neutrino-antineutrino appearance and disappearance fit shows a preference (1.9 sigma) for what is called normal mass ordering: The three neutrino mass states are ordered m1 ≤ m2 ≤ m3.

NOvA is also working to measure one of the least known oscillation parameters, θ23, that governs the degree of flavor mixing in the third mass state. The fit shows a slight preference (1.6 sigma) for the value of this angle to be in the upper octant (θ23 > 45 degrees) and therefore points towards an absence of symmetry in the way muon and tau neutrino flavors contribute to the third neutrino mass state. The data recorded thus far does not allow us to draw conclusions about CP violation in neutrino interactions.

The experiment is scheduled to collect new data until 2025. NOvA collaborators are continually working to improve the experiment and analysis techniques to potentially provide a definitive statement about the neutrino mass ordering, the value of θ23, and strong constraints on the CP-violating phase. These measurements are paramount if we want to understand the neutrino properties and the role they played in the formation of the universe as we know it.

This work is supported in part by the DOE Office of Science and the National Science Foundation.

See the full here.


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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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From Fermi National Accelerator Lab: “Department of Energy awards Fermilab funding for next-generation dark matter research”

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FNAL Art Image by Angela Gonzales

From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

October 18, 2019
Leah Hesla

Earlier this month, the Department of Energy announced that it has awarded scientists at its Fermi National Accelerator Laboratory funding to boost research on dark matter, the mysterious substance that makes up an astounding 85% of the matter in the universe.

The award will fund two Fermilab projects focused on searching for dark matter particles of low mass — less than the mass of a proton.

Over the past 90 years, scientists have found increasing evidence for dark matter, first in the motion of stars and galaxies and more recently in the pattern of temperature fluctuations from the universe’s earliest moments, still seen today. While evidence for dark matter is strong, the nature of dark matter has remained a mystery.

DOE’s Basic Research Needs for Dark Matter New Initiatives program aims to bolster the search for dark matter particles in the range from as heavy as a proton to the lightest mass consistent with the evidence, a million trillion trillion times lighter. It leverages existing and planned large-scale investments and expertise in accelerators, underground laboratories, detector R&D, novel sensing and theoretical physics.

“The mystery of the nature of dark matter is one of the most persistent in particle physics, and it’s only through smart, steady searching that we’ll get to the bottom of it,” said Josh Frieman, head of the Fermilab Particle Physics Division. “Our scientists have been on the cutting edge in the search for low-mass dark matter. The infusion of funding from this award will enable us to advance new approaches that can bring us that much closer to bringing dark matter to light.”

The Fermilab-led initiatives funded through the DOE Basic Research Needs for Dark Matter New Initiatives grants are:

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ADMX, based at the University of Washington, will search for hypothesized dark matter particles called axions. Photo: Mark Stone/University of Washington

1. Extending the search for axions with ADMX

Principal investigator: Andrew Sonnenschein

One theory suggests that dark matter is made of axions, very light, invisible particles streaming through the cosmos. Scientists working on the ADMX experiment have been searching for these hypothesized particles using a haloscope, an instrument that uses a magnet to convert axion dark matter particles into ordinary microwaves. By building the world’s most sensitive superconducting radio receiver, ADMX researchers hope to discover axions at frequencies between 2 and 4 gigahertz.

Collaborating institutions: Lawrence Livermore National Laboratory, Pacific Northwest National Laboratory, Los Alamos National Laboratory, University of Florida, University of Washington, Washington University, St. Louis, University of California, Berkeley and University of Western Australia

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Engineers work on highly sensitive skipper CCDs. Researchers will use these sensors to search for low-mass dark matter particles. Photo: Reidar Hahn

2. Toward unprecedented sensitivity with skipper CCDs

Principal investigator: Juan Estrada

One way to hunt for dark matter is to catch it in the act of bumping into a particle of ordinary matter, such as an electron. A sensitive enough detector could pick up on the transfer of energy between the two. Scientists at Fermilab and partnering institutions have been using high-sensitivity devices called skipper CCDs to catch those energy-transfer signals. Under the new DOE initiative, they’re setting their sights on the even harder-to-detect, lower-energy transfers that would arise from a low-mass dark matter particle. They plan to take the skipper CCD technology to its full potential by developing the design and construction plan for a 10-kilogram experiment with skipper CCDs, building on the developments from the ongoing pathfinder experiments SENSEI and DAMIC.

Collaborating institutions: Pacific Northwest National Laboratory, Stony Brook University, University of Chicago, University of Washington

See the full here.


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Please help promote STEM in your local schools.

Stem Education Coalition

FNAL Icon

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.

#department-of-energy-awards-fermilab-funding-for-next-generation-dark-matter-research, #extending-the-search-for-axions-with-admx-u-washington, #fnal, #toward-unprecedented-sensitivity-with-skipper-ccds

From Stanford University: “Stanford experiment harnesses atoms to detect gravitational waves”

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From Stanford University

September 25, 2019
Erin I. Garcia De Jesus

Hidden deep in a basement at Stanford stands a 10-meter-tall tube, wrapped in a metal cage and draped in wires. A barrier separates it from the main room, beyond which the cylinder spans three stories to an apparatus holding ultra-cold atoms ready to shoot upward. Tables stocked with lasers to fire at the atoms – and analyze how they respond to forces such as gravity – fill the rest of the laboratory.

The tube is an atom interferometer, a custom-built device designed to study the wave nature of atoms. According to quantum mechanics, atoms exist simultaneously as particles and waves. The Stanford instrument represents a model for an ambitious new instrument ten times its size that could be deployed to detect gravitational waves – minute ripples in spacetime created by energy dissipating from moving astronomical objects. The instrument also could shed light on another mystery of the universe: dark matter.

Stanford experimental physicists Jason Hogan and Mark Kasevich never intended for their device to be implemented this way. When Hogan began his graduate studies in Kasevich’s lab, he focused instead on testing gravity’s effects on atoms. But conversations with theoretical physicist Savas Dimopoulos, a professor of physics, and his graduate students – often lured downstairs by an espresso machine housed directly across the hall from Kasevich’s office – led them to start thinking about its utility as a highly sensitive detector.

“We were just talking physics, as physicists often do,” says Kasevich, a professor of physics and applied physics at Stanford’s School of Humanities and Sciences. One thing led to another and the group landed on a bold plan for creating an atom interferometer capable of detecting gravitational waves that no one has seen before.

Their idea fits into another wave sweeping through physics, one that involves co-opting exquisitely sensitive instruments developed for other purposes to answer fundamental questions about nature.

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Physicists Jason Hogan and Mark Kasevich are developing a smaller-scale technique for measuring gravitational waves. (Image credit: L.A. Cicero)

A new detection method

In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected a brief signal from a 1.3 billion-year-old collision between two supermassive black holes. Since then, LIGO has catalogued more gravitational waves passing through Earth, providing astronomers with a powerful new lens with which to study the universe.

MIT /Caltech Advanced aLigo


VIRGO Gravitational Wave interferometer, near Pisa, Italy

Gravitational waves are ripples in space-time, much like ocean waves – except they distort space, not water. In theory, any accelerating mass, whether a waving hand or an orbiting planet, produces gravitational waves. These movements, however, occur at levels far below our ability to detect them. Only gravitational waves from immense astronomical phenomena cause large enough shifts in space-time that they can be recognized by sensors on Earth.

Just as different frequencies make up the electromagnetic spectrum, gravitational waves also vary. LIGO and other current gravitational wave detectors sense a very narrow range – high-frequency waves such as those from the moment two black holes collide – but other parts of the gravitational wave spectrum remain unexplored. And just as astronomers can learn new things about a star by studying its ultraviolet light versus its visible light, analyzing data from other gravitational wave frequencies could help solve mysteries of space that are currently out of reach, including those about the early universe.

“We identified a region of the spectrum that wasn’t well-covered by any other detector, and it happened to be a match for the methods that we were already developing,” said Hogan, an assistant professor of physics in the School of Humanities and Sciences.

During Hogan’s graduate studies, he and his colleagues constructed the 10-meter-tall atom interferometer to test some of their ideas. However, in order to increase the sensitivity of the device – necessary to detect space-time wiggles smaller than the width of a proton – they need a bigger detector. And thus the 100-meter Matter-wave Atomic Gradiometer Interferometric Sensor, or MAGIS-100, experiment was born.

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With help from a $9.8 million grant from the Gordon and Betty Moore Foundation, scientists plan to make an existing underground shaft at Fermilab, a Department of Energy National Laboratory in Illinois, MAGIS-100’s new home.

“You can find holes in the ground, but it’s kind of hard to find a hole in the ground with a lab attached to it,” said Rob Plunkett, a senior scientist at Fermilab involved with the project.

Conceptually, MAGIS-100 will work similar to LIGO. Both experiments harness light to measure the distance between two test masses, much like radar ranging. But while LIGO has mirrors, MAGIS-100 favors atoms.

“The atom turns out to be an amazing test mass for these purposes,” said Hogan. “We have very powerful techniques for manipulating it and allowing it to be insensitive to all the background sources of noise.”

LIGO’s mirrors hang on glass threads, meaning that an earthquake could set off its sensors. MAGIS-100, on the other hand, has measures in places to prevent such sources of extraneous noise from affecting its data.

After being cooled to a fraction of a degree above absolute zero, the atoms are dropped vertically into the shaft like dripping water droplets from a faucet. The frigid temperature puts the atoms into a state of rest, so they remain still as they fall, and because the shaft is a vacuum, the atoms plummet without risk of veering off course. The shaft’s vertical orientation also ensures that a shaking Earth won’t affect the measurements.

Lasers then manipulate the falling atoms and the team can measure how long they are in an excited state. Hogan and Kasevich hope to employ strontium as their test mass – the same element used in atomic clocks – to determine whether there are any time delays when light excites atoms. A delay would suggest a gravitational wave passed through.

In addition, MAGIS-100 scientists can use the atomic data to test predictions made by dark matter models. According to some models, the presence of dark matter could lead to variations in atomic energy levels. The supersensitive laser technology allows Plunkett and collaborators to look for these variations.

Looking toward space

MAGIS-100 is a prototype, another step toward building an even larger device that would be many times more sensitive. Hogan and Kasevich said they envision one day building something on the scale of LIGO, which is 4-kilometers long.

Because a future full-scale MAGIS-100 should detect low-frequency gravitational waves around 1 Hertz, such as those emitting from two black holes orbiting around each other, it could identify the same events that LIGO has already seen, but before the masses actually collide. The two experiments could thus complement one another.

“We could make a detector that could see the same system, but much, much younger,” said Hogan.

Advanced MAGIS-style detectors might also find sources of gravitational waves that fly under LIGO’s radar. Primordial gravitational waves, for example, produced moments after the Big Bang.

“Detecting gravitational waves that originated from the early universe can shed light on what actually happened,” said Kasevich.

No one knows the frequencies of these primordial gravitational waves or whether the future large-scale detector can pick them up. Hogan said that he believes as many detectors as possible should be built in order to cover a broad range of frequencies and simply see what is out there.

“The known sources that are exciting are these LIGO-like sources,” said Hogan. “Then there are the unknown, which we should be open to as well.”

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From Fermi National Accelerator Lab: “Cool and dry: a revolutionary method for cooling a superconducting accelerator cavity”

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From Fermi National Accelerator Lab , an enduring source of strength for the US contribution to scientific research world wide.

September 24, 2019
Charles Thangaraj

Fermilab scientists and engineers have achieved a landmark result in an ongoing effort to design and build compact, portable particle accelerators. Our group successfully demonstrated a new, efficient way to cool superconducting accelerator components, cutting down on the bulk of the traditional cooling infrastructure needed for this technology.

The importance of this advance is apparent if you happen to walk around the Fermilab site. You really can’t miss it: Particle accelerators built for discovery are big machines. They stretch for hundreds of meters, even kilometers. They also require large and complex infrastructure, which restricts their use primarily to science research laboratories.

And yet, particle accelerators are very useful tools outside science research labs. They have applications in security, medicine, manufacturing, and roadways. And their impact might be even greater if we could make these traditionally giant machines compact. Miniaturize them. Design high-power accelerators that could fit, literally, inside the back of a truck.

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For the first time, a team at Fermilab has cooled and operated a superconducting radio-frequency cavity — a crucial component of superconducting particle accelerators using cryogenic refrigerators, breaking the tradition of cooling cavities by immersing them in a bath of liquid helium. It achieved an accelerating gradient of 6.6 million volts per meter. Photo: Marty Murphy

At Fermilab, we relish such practical physics challenges. And last month, our team rose to the challenge, achieving a major milestone in our quest to realize powerful, compact accelerators that have an impact on our everyday lives. The core team included Ram Dhuley, Michael Geelhoed, Sam Posen and Charles Thangaraj.

Combining a verve for practicality with cutting-edge science, our team successfully demonstrated a new, revolutionary method for cooling a superconducting accelerator cavity without using liquid helium — counterintuitive for most in accelerator science.

This new method — based on a Fermilab idea patented five years ago — uses cryogenic refrigerators, or cryocoolers, for removing the heat dissipated by a superconducting accelerator cavity. By compressing and expanding helium gas across a regenerative heat exchanger in a “closed” cycle, the cryocoolers produce cooling without letting the helium out. This closed-cycle operation of cryocoolers makes our system very compact — more so than the standard liquid helium cooling equipment used by traditional accelerator cavities.

Superconducting cavities are crucial components in particle accelerators, propelling the particle beam to higher energies by giving it an electromagnetic push. We used a 650-megahertz niobium cavity, and we all watched with pride the first successful results delivered by our new method: an accelerator gradient of 6.6 million volts per meter. That is already sufficient for the applications we have in mind, and still, we know we can do better.

Superconducting cavities used in large accelerators are usually cooled to around 2 kelvins, colder than the 2.7 kelvins (minus 455 degrees Fahrenheit) of outer space. The typical way to achieve this is by immersing the cavities in liquid helium and pumping on the helium to lower its pressure, and therefore its temperature. All of this requires large and complex cryogenic systems – a factor that severely limits the portability and therefore the potential applications of superconducting accelerators in industrial and other environments.

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Celebrating the success of the first results from the conduction-cooling project are, from left: Michael Geelhoed, Ram Dhuley, Sam Posen and Charles Thangaraj. Photo: Laura Rogas

Our team broke this barrier by successfully realizing a technique conceptualized by Fermilab physicist Bob Kephart, now retired. The technique proposed to make superconducting accelerators practical by 1) coating a thin layer of a material called niobium-tin to the inside of the niobium cavities, and 2) cooling the coated cavities using cryocoolers via conduction links connecting the two. The cryocooler-cavity setup dispenses with a bath of cryogenic liquid and any need for a cryogenic plant to achieve superconductivity.

The demonstration also shows how this method could simplify superconducting accelerators and make them accessible for broader needs beyond basic science – better pavements, wastewater treatment, medical device sterilization, and advanced manufacturing.

Applying the scientific breakthroughs at Fermilab and transforming them to solve challenges outside fundamental science involves systematic entrepreneurial thinking – identifying an opportunity and asking and answering a whole host of questions to validate the opportunity. A great value in all of this is converting DOE’s investment in science and technology into innovation that could allow new industries to emerge.
At Fermilab, we will continue to apply our frontier technologies for novel applications beyond discovery science. This major breakthrough is an exciting step in that direction, and we will continue to push the envelope.

This project is supported by the Laboratory Directed Research and Development Program at Fermilab. The work is also supported by the DOE Office of Science.

Charles Thangaraj is the science and technology manager at Fermilab’s Illinois Accelerator Research Center.

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