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Posts Tagged ‘R&D’

Mu2e attracts magnet experts

Wednesday, December 18th, 2013

This article appeared in symmetry on Dec. 16, 2013.

By tapping into specialized knowledge around the world, the Mu2e collaboration will undertake a first-of-its-kind experiment. Image courtesy of Lawrence Berkeley National Laboratory

By tapping into specialized knowledge around the world, the Mu2e collaboration will undertake a first-of-its-kind experiment. Image courtesy of Lawrence Berkeley National Laboratory

Fermilab’s Mu2e experiment is unlike anything ever attempted. So when the collaboration needed a first-of-its-kind magnet prototype built, they turned to an institution known for its magnet expertise: the Genoa section of the Italian Institute for Nuclear Physics, or INFN, located in the University of Genoa in Italy.

Earlier this year, INFN-Genoa became the sixth Italian institution to join the Mu2e collaboration, which now sports more than 150 members from 28 labs and universities in the United States, Italy and Russia. The team of magnet experts there has decades of experience working on high-energy physics experiments—they helped design and build magnets for BaBar at SLAC and, more recently, the CMS detector at CERN.

Now they’re putting that knowledge toward building prototypes of the years-in-development magnets that will be used for for Mu2e, an experiment intended to study whether charged particles called leptons can change from one type to another. According to Doug Glenzinzki, the deputy project manager for Mu2e, the experiment’s goal is to narrow down the possibilities for completing physicists’ picture of the universe, by amassing evidence for one theory over others.

“We know the Standard Model is incomplete,” Glenzinski says. “The number one goal of particle physics is to elucidate what a more complete model looks like. There are a lot of theories, and we are looking for data that tells us which is right.”

The Mu2e apparatus includes a detector solenoid, a transport solenoid and a production solenoid. Image courtesy of: Mu2e Collaboration

The Mu2e apparatus includes a detector solenoid, a transport solenoid and a production solenoid. Image courtesy of: Mu2e Collaboration

It turns out, Glenzinski says, “charged lepton flavor violation”—the phenomenon Mu2e is being built to study—is a powerful way of discriminating between possible models. Seeing this violation would also open up new questions about a theory of nature that has stood for 80 years. In short, this experiment could point the way toward the future of particle physics.

Mu2e will use a 92-foot-long detector with a unique design. It will be built in three sections, each its own superconducting solenoid, which is a set of electromagnetic coils that generates the particular magnetic fields required for the experiment. The detector consists of a production solenoid, a detector solenoid and a snake-like transport solenoid connecting them. Fermilab’s accelerators will fire a beam of protons into the production solenoid, where they will strike a target to produce pions. It’s the job of the transport solenoid to winnow down that beam of pions as it moves through, herding negatively charged muons to the detector solenoid and sending other unwanted particles out of the way.

The transport solenoid—a 42-foot-long curved pipe—will use 50 different magnets to accomplish this. The Genoa team will build prototypes of these magnets, working from years of design and engineering by Fermilab’s Technical Division, an effort led by Giorgio Ambrosio, Mike Lamm and Tom Page.

Pasquale Fabbricatore is one of the leaders of the Genoa team—he worked on both the BaBar and CMS magnets. He says that though the Mu2e magnets will use similar technology to large detector magnets, their unusually small size—about 6.5 feet in diameter—makes applying that technology tricky.

This sample holder is used to test the prototype conductor for the Mu2e experiment's transport solenoid. Photo: INFN-Genoa Mu2e Collaboration

This sample holder is used to test the prototype conductor for the Mu2e experiment’s transport solenoid. Photo: INFN-Genoa Mu2e Collaboration

“Superconducting magnets are so particular that each one is a prototype,” Fabbricatore says. “Each unique magnet has unique problems.”

For example, Fabbricatore says, the prototype magnet will consist of a module containing two electromagnetic coils, installed close together through a shrink-fitting operation. While placing the first one should be easy, he says, warming the second coil up to the right temperature to install it without damaging the first could prove to be difficult.

“This is a problem we have never encountered before,” he says.

INFN-Genoa is just the latest Italian institution to join the Mu2e team. Glenzinski says the experiment has received strong support from Italy since the project’s inception. Italy is now contributing to Mu2e with four INFN groups from Frascati, Pisa, Udine and Lecce. It also leads the building of the calorimeter system, which helps measure the momentum of electrons and identify background signals. Glenzinski says the Genoa group makes a fine addition to a growing collaboration.

“Pasquale and his team are world-class magnet experts,” Lamm says. “They’re a great addition to the Mu2e collaboration and we’re excited to have them join us.”

The work on the new magnet began in September, and Fabbricatore says the prototype will be delivered to the collaboration in July 2014. Glenzinski says that fits the experiment’s timeline nicely. The collaboration will test the prototype, then send it out to a vendor to create the 50 magnets needed for the project. Assembly of the Mu2e detector should begin in 2016, with the experiment ready to take data by the end of 2019.

Andre Salles

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VERTEX 2012

Friday, October 5th, 2012

Seth talking at the VERTEX2012 conferenceNever mind my complaints about travel, VERTEX 2012 was a very nice conference. There were a lot of interesting people there, mostly much more expert than me on the subject of vertex detectors. (I’ve written before about how tracking works and how a pixel detector works. In general, a vertex detector is a high-precision tracker designed to measure exactly where tracks come from; a pixel detector is one type of vertex detector.) My talk was about the current operations of the CMS pixel detector; you can see me giving the talk at right, and the (very technical) slides are here. Other talks were about future development in on-detector chip and sensor technology; this work is likely to affect the next detectors we build, and the upgrades of our current detectors as well.

VERTEX 2012 Conference attendees at Sunrise Peak, JejuThe location of the conference — Jeju, Korea — was also very nice, and we got an afternoon off to see some of the island. The whole island is volcanic. The central mountain dominates the landscape, and there are lots of grass-covered craters. Sunrise peak, at left, erupted as recently as 5,000 years ago, but it seemed pretty quiet when we were there.

Overall, the conference was a great opportunity to meet people from all over the world and learn from them. And that’s really why we have to travel so far for these things, because good people work everywhere.

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From left: Fermilab Deputy Director Young-Kee Kim; Gina Rameika, PPD; Kevin Bomstad and Jason Whittaker, Whittaker Construction and Excavation; Dixon Bogert, Fermilab; Mike Weis, DOE; Fermilab Director Pier Oddone; Erik Gottschalk, PPD. Photo: Reidar Hahn

This article first appeared in Fermilab Today on Jan. 24.

Despite the biting cold and snow, scientists and Fermilab personnel gathered outside to break ground for Fermilab’s new Liquid Argon Test Facility. The facility, expected to be completed spring 2013, will house liquid-argon based experiments.

Scientists have speculated since the 1980s that liquid argon could be used as a crash pad for high-energy neutrinos and have subsequently constructed several liquid-argon neutrino detectors; the largest and most prominent being ICARUS, the Imaging Cosmic And Rare Underground Signals, detector in Italy. The design of the new MicroBooNE experiment improves upon technology developed for ICARUS and will allow scientists to observe neutrinos with greater precision and resolution.

Regina Rameika is the project manager for the construction of the MicroBooNE detector.

“The MicroBooNE detector that will first use this facility is smaller than ICARUS, but incorporates some advanced designs,” Rameika said.

MicroBooNE will use liquid argon as a target for neutrinos generated in the Booster neutrino beam. When the neutrinos hit the argon nuclei, they generate showers of charged particles that then drift to an electrical detector. The purer the argon, the further the particles are able to drift. MicroBooNE will use ultrapure argon to maximize the distance these particles drift. This model is more efficient, cost effective, and has the potential to be scaled-up to a much larger size than previous detectors.

The MicroBooNE experiment will provide another layer of data for using the Booster neutrino beam. Not only will scientists be able to observe particles with the existing MiniBooNE detector, but now they will be able to measure neutrinos from the Booster neutrino beam with a second, higher-resolution detector.

“The MicroBooNE experiment will be focused on understanding some anomalies observed in the data from the MiniBooNE experiment,” Rameika said. This project will also provide valuable insight into different designs for liquid-argon detectors that could be located in the LArTF once MicroBooNE is complete.

—Sarah Charley

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This column by Fermilab Director Pier Oddone appeared in Fermilab Today on Jan. 17.

Last week we hosted the US-UK Workshop on Proton Accelerators for Science and Innovation. The workshop brought together scientists from the United States and the United Kingdom who are working on high-intensity proton accelerators across a variety of fronts. The meeting included not only the developers of high-intensity accelerators but also the experimental users and those involved in the applications of such accelerators beyond particle physics.

At the end of the conference, John Womersly, CEO of the UK’s Science and Technology Facilities Council, and I signed a letter of intent specifying the joint goals and activities of our collaboration for the next five years. We plan to have another workshop in about a year to review progress and explore additional areas of collaboration.

Our collaboration with scientists from the United Kingdom in the area of high-intensity proton accelerators is already well established. We have a common interest in muon accelerators, both in connection with neutrino factories and muon colliders. Both of these future projects require multi-megawatt beams of protons to produce the secondary muons that are accelerated. We collaborate on the International Muon Ionization Cooling Experiment at the Rutherford Appleton Laboratory. MICE is the first muon cooling experiment and an essential step in the road to neutrino factories and muon colliders. We also collaborate on the International Scoping Study for neutrino factories.

In our current neutrino program we are very appreciative of this collaboration and U.K. expertise in the difficult mechanical design of high-power targets, in particular for the MINOS, NOvA and LBNE experiments. The design of these targets is quite challenging as the rapid deposition of energy creates shock waves that can destroy them.The Project X experimental program also depends on having appropriate megawatt-class targets relatively close to experimental set-ups.

One of the primary interests in applications outside of particle physics is the development of intense proton accelerators that could be used for the transmutation of waste or even the generation of electrical power in subcritical nuclear reactors. The accelerators necessary for such subcritical reactors could not have been built just a decade ago, but the advent of reliable superconducting linacs changed that. Several programs abroad are developing such accelerators coupled to reactors. While the United States has no explicit program on accelerator-driven subcritical systems, the technologies that we are developing for other applications, such as Project X, place us in a good position should the United States decide to develop such systems.

Overall, the workshop was very productive and the areas of potential collaboration seemed to multiply through the meeting. Each one of the five working groups is preparing a brief summary of the potential areas of collaboration as well as a specific and focused plan for the next year.

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This article first appeared in Fermilab Today on Oct. 7.

A muon collider is closer to reality after a successful high-pressure hydrogen gas-filled RF (HPRF) cavity beam test at Fermilab. The test, conducted in the MuCool Test Area (MTA) at Fermilab by the MuCool collaboration, shows the beginnings of a practical solution to a difficult obstacle.

From left: Ben Freemire, Katsuya Yonehara, Mukti Jana, Moses Chung and Giulia Collura standing behind the HPRF cavity (under the hood) and beam pipe section. Photo: Yagmur Torun, R&D

“This was years in the making,” said MTA coordinator Yagmur Torun. “This idea of using HPRF cavities for muon cooling was first proposed in the early 2000s.”

Muons, a heavier version of electrons, are elementary particles. They cannot break down into smaller components, like protons decaying into gluons and quarks. Muons have nearly 200 times the mass of electrons. Electrons would lose too much energy circling in an accelerator, while muons retain enough energy to reach collision speeds.

The problem is that the muons come into existence as a hot gas, which is much too large to fit through a conventional accelerator without beam cooling.

Muons also do not live long enough to complete the acceleration if standard beam cooling methods are used. With only 2.2 microseconds to accelerate and collide, every instance of muon action must be carefully controlled. Ionization cooling is the only practical method that is fast enough for muons and the MuCool R&D program at Fermilab is aimed at developing components for muon cooling.

For muon cooling, RF cavities are used to accelerate particles within a strong magnetic field. The magnets help contain and focus the beam of particles. However, there were significant problems with the RF cavities, as scientists found that the cavities did not work well inside the magnets.

“The cavity would break down, or start arcing. It was unusable,” said Torun, assistant professor at Illinois Institute of Technology with a joint appointment at Fermilab’s Accelerator Physics Center (APC). “There were various ways to attack the problem, but then Rolland Johnson suggested we fill the cavities with gas.”

Rolland Johnson, a physicist who worked at Fermilab for 30 years and founded Muons, Inc., introduced the novel concept of filling the RF cavities with hydrogen. The hydrogen gas would suppress the electrons stripped from the cavity surface, which had previously caused the breakdown of the cavity.

The beam pipe leading into the solenoid magnet, with the HPRF cavity installed in the MTA experimental hall. Photo: Yagmur Torun, R&D

Physicists currently use RF cavities to bunch charged particles and move them forward through an accelerator. A standing wave, set at a particular frequency, pushes the beam particles forward to the next cavity.

“In 2005, we tested the hydrogen gas in the RF cavity,” Katsuya Yonehara, Peoples Fellow at the APC and spokesperson for the HPRF beam test, said. “The results were promising. We saw the cavity would work in a magnetic field, but we had a remaining question—could a very intense muon beam cause the field in the cavity to collapse?”

In 2007, a beam line from the Fermilab Linac accelerator was installed in the MTA. It took four years of adjustments and upgrades before the beam line was ready for the test in July of this year.

“It worked,” Torun said. “The cavity didn’t break down. This is a big step in our search for a potential path for muon colliders and accelerators at Fermilab.”

In the next few months, there will be a more detailed study.

“We’re adjusting the cavity, and making improvements for studying its application to muon acceleration,” Yonehara said. “We’re seeing progress.”

—Ashley WennersHerron

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Fermilab issued this press release today.

Alex Romanenko, sitting on the edge of a large cryogenic vessel, holds one of the superconducting RF cavities made of niobium. Photo: Fermilab (Click on image for larger version)

Alex Romanenko, a materials scientist at Fermi National Accelerator Laboratory, will receive $2.5 million from the Department of Energy’s Office of Science to expand his innovative research to develop superconducting accelerator components. These components could be applied in fields such as medicine, energy and discovery science.

Romanenko w as named a recipient of a DOE Early Career Research Program award for his research on the properties of superconducting radio-frequency cavities made of niobium metal. The prestigious award, which is given annually to the most promising researchers in the early stages of their careers, includes a $2.5 million award over five years to continue work in the specified area.

“Dr. Romanenko and his proposed research show great promise,” said Tim Hallman, associate director of the DOE’s Office of Science for Nuclear Physics. “We are pleased that he has been selected to receive an Early Career Research Program award to continue this work.”

Romanenko’s work could explain why some superconducting radio frequency cavities are highly efficient at accelerating charged particles to high speeds while others are not, as well as prescribe new ways to make cavities even more powerful. His research links t he performance of SRF cavities to the quality of the niobium metal used to make them. In particular, he investigates specific defects and impurities in niobium. Although scientists take painstaking measures to ensure that the niobium is completely pure and that the final SRF cavities are free from any contaminants, dust or debris, the cavities do not always perform the way that they should. Romanenko’s research is dedicated to finding out why that happens.

Romanenko began his research on SRF cavities as a graduate student at Cornell University, an institution known for its SRF research. He continued his award-winning work at Fermilab when he joined the laboratory in 2009 as a Peoples Fellow, a prestigious position given to scientists who have the potential to be leaders in their field. (More information at
http://www.fnal.gov/pub/today/archive_2011/today11-03-02.html )

Through his research, Romanenko found that a new, previously unexplored, type of defect near the cavity surface may result in surface differences that are responsible for a cavity’s inferior performance. What he found was surprising: the defect sites often contained niobium-hydrogen compounds, which might form when the cavities are prepared for operation. Specifically, he was able to pinpoint the problematic area to the first 40 nanometers of a cavity’s surface, a thickness equivalent to 120 layers of niobium atoms.  

“The technology of these cavities has developed so fast recently that it is ahead of the corresponding science,” Romanenko explained. “We know how to make them work to a certain level of performanc e, but do not necessarily understand the full physics behind why they do so. I hope to understand why cavities behave in certain ways first, improve on this and then apply what I learn to other materials.”

If Romanenko can isolate the specific nanostructural effects that cause problems in cavities, then Lance Cooley, Romanenko’s supervisor and head of the new Superconducting Materials Department in Fermilab’s Technical Division, is prepared to direct other scientists to develop ways to prevent or control them and transfer that knowledge to industry. This could someday make it possible to mass-produce nearly perfect niobium cavities as well as lay the groundwork for cavities made from other superconducting materials that can perform at higher temperatures and accelerating fields. Such high-performance cavities—strung together to create powerful, intense particle beams—would lead to accelerators that can be used in indust ry, in hospitals and at research institutions. These accelerators are needed, for example, to produce a range of radioisotopes for medical diagnostics and have the potential to treat nuclear waste, among other applications. (More information at http://www.acceleratorsamerica.org/applications/index.html)

Strung together like the pearls of a necklace and cooled to ultralow temperatures, SRF cavities can accelerate particles with high efficiency. Photo: Fermilab (Click on image for larger version)

“This award recognizes the high caliber of research that takes place at Fermilab,” Cooley said. “It is because of the laboratory’s existing world-class research program that Alex’s research is likely to succeed.”

The monetary award will cover part of Romanenko’s research efforts, fund a postdoctoral associate and a part-time technician, and pay for advanced analysis techniques used to examine surfaces in the next five years.

Fermilab is a national laboratory supported by the Office of Science of the U.S. Department of Energy, operated under contract by Fermi Research Alliance, LLC.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov

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This article appeared in ILC Newsline July 28.

Editor’s note: Fermilab has been working with national and international institutions to develop superconducting radio-frequency cavities and their encapsulating cryomodules for next-generation accelerators, including the proposed International Linear Collider and the proposed Project X.

CM1 with its recently installed RF distribution system ready for testing. Image: Jerry Leibfritz

SRF technology enables the acceleration of intense beams of particles to high energies more efficiently and at lower costs than other technologies. SRF technology could also be applied in the areas of clean nuclear energy and transmutation of radioactive waste.

Cryomodule 1 is now firing on all eight cavities.

Cryomodule 1, Fermilab’s test cryomodule for ILC-type accelerating cavities and superconducting radiofrequency (SRF) technology, was powered up as a complete, multi-cavity instrument earlier this month. Previously, researchers had delivered power only to the individual cavities inside it.

“We’ve operated superconducting cavities before, but this is the next step in scale,” said Sergei Nagaitsev of Fermilab’s Accelerator Division. “Operating a single cavity in its own cryostat is comparable, but with a full cryomodule, the complexity goes up by an order of magnitude.”

Since the cool-down of CM1 last November, scientists and engineers have been busy installing the plumbing for power distribution, called waveguides; upgrading the water skid, which helps with the cooling of the high-power RF equipment; and taking data on each cavity’s accelerating gradient and quality factor, or Q. Researchers completed the cavity tests in June.

“The big question now is how this module performs compared to when the cavities were at DESY,” said Fermilab’s Elvin Harms. The German physics lab DESY provided all eight CM1 cavities, which were tested before they came across the Atlantic. Over the coming weeks, researchers will continue to feed power into cryomodule to gather data on how cavities perform as a single unit rather than as individual elements. The hope is that their gradients and Q will be in reasonable agreement with DESY’s numbers.

To make sure the data that comes through is reliable, the CM1 team will work on calibrations, test RF power operation, and work the kinks out of the system. Then comes a multi-week programme where scientists will perform stability tests and beam studies for the ILC beam current programme, which includes tests that can be conducted without the presence of beam. Researchers will also use CM1 for tests for Project X, Fermilab’s proposed proton accelerator programme.

Not all sailing was smooth in the time since the November cool-down. Some cavities still have wrinkles that need to be ironed out.

“Nevertheless, the fact that the integration of it all into a single system worked is a tremendous boost for the Accelerator Division, the Technical Division and our collaborators,” Nagaitsev said.

Collaborators on CM1 include researchers from DESY, INFN in Italy and KEK in Japan.

“Many people have invested a lot of time in CM1,” Harms said. “They’ve been eagerly waiting to get this to this day.”

– Leah Hesla

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This story appeared in Fermilab Today July 29.
PHENIX, one of two major experiments located at the Relativistic Heavy Ion Collider (RHIC) based at Brookhaven National Laboratory, is upgrading again with help from Fermilab’s Slicon Detector Facility (SiDet). Fermilab technicians finished assembling hundreds of forward silicon vertex tracker (FVTX) detector components in early July.

One of the hundreds of forward silicon vertex tracker (FVTX) components assembled at Fermilab's Silicon Detector Facility. Photo: Vassili Papavassiliou, New Mexico State University

The wedge-shaped components will be installed in PHENIX to help scientists study the properties of quark gluon plasma (QGP), which theorists believe made up the universe moments after the Big Bang.

Eric Mannel, a physicist from Columbia University and one of about 450 PHENIX contributors, worked as an electronics project engineer overseeing the final stages of assembly at Fermilab.

“We want to understand how the universe evolved the way it did from the very beginning,” Mannel said. “The FVTX detector will provide a higher resolution for tracking of particles which will allow us to study the properties of QGP.”

QGP is a near-perfect liquid composed of disassociated quarks and gluons suspended in plasma. It is said to be nearly perfect because it contains almost no internal friction—if you were to stir the plasma, it would continue to swirl forever. Physicists create QGP by smashing heavy ions and protons together. SiDet personnel provided a technical capabilities unique to Fermilab, to construct detectors that will allow physicists to study those collisions in more detail than ever before.

“We anticipate that we’ll be able to reconstruct secondary vertices from the decay of charm and beauty quarks with a resolution of 70 microns. The typical decay lengths for those particles are several hundred microns in heavy-ion collisions at RHIC,” Mannel said. The average human hair is about 100 microns thick.

The SiDet team completed the microassembly of FVTX components in mid-July. From left to right: Tammy Hawke, Michelle Jonas, Nina Ronzhina, Bert Gonzalez and Mike Herron. Also part of the group is Hogan Nguyen, not pictured. The FVTX group of PHENIX collaborators are also not pictured: Eric Mannel, Vassili Papavassiliou, Elaine Tennant, AAron Veicht and Dave Winter. Photo: Reidar Hahn.

AAron Veicht, a Ph.D. student at Columbia University, spent nearly 10 months working with the technicians at SiDet and will be part of the team installing the detector in PHENIX this fall.

“I’ll get to see the project from the very early stages all the way through to analyzing the data, so it’s very exciting,” Veicht said. “I gained a lot of experience while working with the technicians at Fermilab. It was a vital part of my education.”

Bert Gonzalez was the Fermilab technical supervisor on the design project. “The process went quite well, as this was the first endeavor where we worked with program collaborators,” Gonzalez said. Gonzalez and his Fermilab team spoke with PHENIX collaborators via conference calls for most of the design and development of the components.

“It was a good run,” Gonzalez said. “The project will be missed at SiDet, because it was a concrete job; you could dig your hands into it.”

Veicht felt that the people at SiDet were helpful and knowledgeable.

“It was my first time at Fermilab, and it was absolutely fantastic,” Veicht said.

PHENIX detector. Photo: Brookhaven National Laboratory

PHENIX collaborators plan to commission the detector in October and begin data collection this January.

- Ashley WennersHerron

Related information:

*PHENIX website

*RHIClets: A collection of Java applet games about the RHIC collider and RHIC physics.

*PHENIX cartoons

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This article first appeared in Fermilab Today July 20.

During the last week of June, roughly 100 physicists met in the thin air of Telluride, Colo., to contemplate the construction and physics goals of a muon collider. This new type of particle collider would be one of the most complex devices ever created by humans. It would employ a short-lived particle, the muon, which disintegrates in a mere 2 millionths of a second. That’s just long enough to use the particle as a probe to unveil the secrets of nature.

The muon collider plans and designs are still conceptual, and we won’t be building such a machine for at least 20 years. Undaunted, the scientists at Telluride trekked on to identify and solve the multifarious issues that revolve around three topics:

*creating a large number of muons and antimuons for the collider using the proposed Project X accelerator

*cooling these particles to form small packets that can be accelerated to an energy of up to 2 TeV

*making the muons and antimuons collide head on at 4 TeV in a complex and robust particle detector

For the detector design, the challenge is to differentiate between the particles coming from actual muon-antimuon collisions and the enormous background created by particles coming from muon decays. At the Telluride meeting, scientists reported a feasible solution: a detector that utilizes fast timing and clever geometry to deal with the ferocious backgrounds. Major, more detailed, studies need to be done before this type of detector becomes a reality.

Theorists provided a list of the “top six” key physics questions to explore 20 years from now, when a muon collider exists. The list includes:

*studying a very heavy, beyond-the-Standard Model Higgs boson, via WW scattering, which would be difficult to detect at the LHC

*probing in depth the collider production of dark matter particles

*studying a Z’-boson, should the LHC find evidence of such a particle. If it exists, a Z’ boson will act as an amplifier for new physics, and this would reduce the stringent technological requirements for muon cooling and background reduction.

The muon collider complex would fit on the Fermilab site and could be built in functional stages, beginning with the Project X proton accelerator. The next stage would be the construction of a large muon storage ring, or neutrino factory, followed by the construction of the muon collider itself. Staging distributes the costs over many years and many sub-projects and might be the way for the United States to once more host experiments at the Energy Frontier.

– Fermilab theorist Chris Hill

Related information:

Muon collider website

Muon collider program website

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Project X chopper challenge

Thursday, May 5th, 2011

This story appeared in Fermilab Today May 5.

Two Fermilab deflector prototypes being considered for the Project X chopper. In both cases, each rectangular copper plate sets up an electrostatic pulse that kicks the bunch farther and farther away from the beamline, chopping it out.

At the recent Project X collaboration meeting, attendees confronted the proposed accelerator’s wide-band chopper, a system that would allow scientists to cherry-pick particle bunches from beams to be routed to multiple experiments.

Though its design is a formidable challenge, researchers now believe it’s a workable problem.

“The meeting was the first time we were confident there’s a solution,” said Steve Holmes, Project X project manager. “There are options that look like they’ll work.”

The chopper would lend the proposed Project X a kind of maneuverability not seen in other accelerators.

Different particle physics experiments call for different bunch patterns. A chopper helps create the required pattern by using electric fields to selectively pick off bunches from a steady stream of particles. Bunches in the beam that are left alone accelerate toward an experiment’s target.

With only one target, the chopper’s job can be straightforward: leave every nth bunch alone.

With more than one target, as in the case of Project X, the chopper has to send a far more complicated bunch pattern down the particle conveyor belt. It must also work in concert with a splitter, or router, to direct the right bunches to the different experiments.

“A chopper combined with a splitter is a new twist on the idea,” said Sergei Nagaitsev of Fermilab’s Accelerator Division. This new twist will give scientists the freedom to put in any pattern they like while efficiently serving up bunches for multiple experiments.

“We wanted the project to be as flexible as possible,” Nagaitsev said. “So this chopper is one of the strongest selling points for Project X.”

Collaborators from Fermilab, Lawrence Berkeley National Laboratory and SLAC are pursuing various technical options for the system.

“Nobody’s done anything like this before, but it’s the key to making the whole thing work,” Holmes said.

— Leah Hesla

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