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Posts Tagged ‘Mu2e’

Prototype of Mu2e solenoid passes tests with flying colors

Tuesday, August 11th, 2015

This article appeared in Fermilab Today on Aug. 11, 2015.

This prototype represents one of 27 modules that will make up a critical section of the Mu2e experiment, the transport solenoid. Photo: Reidar Hahn

If you’ve ever looked at a graphic of Fermilab’s future Mu2e experiment, you’ve likely noticed its distinctive, center s-shaped section. Tall and wide enough for a person to fit inside it, this large, curving series of magnets, called the transport solenoid, is perhaps the experiment’s most technologically demanding piece to build.

Last month a group in the Fermilab Technical Division aced three tests — for alignment, current and temperature — of a prototype transport solenoid module built by magnet experts at Fermilab’s Technical Division and INFN-Genoa in Italy.

The triple milestone means that Fermilab can now order the full set for production — 27 modules.

“The results were excellent,” said Magnet Systems Department scientist Mau Lopes, who is leading the effort.

There’s not much wiggle room when it comes to the transport solenoid, a crucial component for the ultrasensitive Mu2e experiment. Mu2e will look for a predicted but never observed phenomenon, the conversion of a muon into its much lighter, more familiar cousin, the electron, without the usual accompanying neutrinos. To do this, it will send muons into a detector where scientists will look for particular signatures of the rare process.

The transport solenoid generates a magnetic field that deftly separates muons based on their momentum and charge and directs slow muons to the center of the Mu2e detector. The maneuver requires some fairly precisely designed details, not the least of which is a good fit.

When put together, the 27 wedge-shaped modules will form a tube with the snake-like profile. Muons will travel down this vacuum tube. To guide them along the right path to the detector, the solenoid units must align with each other to within 0.2 degrees. The Magnet Systems team exceeded expectation: The prototype was aligned with 100 times greater precision.

The team achieved not just the right shape, but the right current. The electrical current running through the solenoid coil creates the magnetic field. The Mu2e team exceeded the nominal current of 1,730 amps, reaching 2,200 amps. As a bonus, while that amount of current has the potential to create a slight deformation in the module’s shape, the Mu2e team measured no change in the structure.

Nor was there much change in the model’s temperature, which must be very low. The team delivered 2.5 watts of power to the coil — well above what the coils will see when running. The module proved robust: The temperature changed by a mere whisker — 150 millikelvin, or 0.27 degrees Fahrenheit. The coils will be at 5 Kelvin when operating. The prototype sustained the nominal current at up to 8 Kelvin.

Fermilab has selected a vendor to produce the modules. Lopes expects that it will be two and a half years until all modules are complete.

“We thank all the smart people at INFN Genoa, the Fermilab Test and Instrumentation Department, the Magnet Systems Department and the Accelerator Division Cryogenics Department for this achievement,” Lopes said. “These seven months of hard work have paid off tremendously. Our project continues at full steam ahead.”

—Leah Hesla

Tags: Fermilab, magnets, Mu2e, R&D
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Mu2e breaks ground on experiment seeking new physics

Tuesday, April 21st, 2015

Fermilab

This article appeared in Fermilab Today on April 21, 2015.

Fermilab’s Mu2e groundbreaking ceremony took place on Saturday, April 18. From left: Alan Stone (DOE Office of High Energy Physics), Nigel Lockyer (Fermilab director), Jim Siegrist (DOE Office of High Energy Physics director), Ron Ray (Mu2e project manager), Paul Philp (Mu2e federal project director at the Fermi Site Office), Jim Miller (Mu2e co-spokesperson), Doug Glenzinski (Mu2e co-spokesperson), Martha Michels (Fermilab ESH&Q head), Mike Shrader (Middough architecture firm), Julie Whitmore (Mu2e deputy project manager), Jason Whittaker (Whittaker Construction), Tom Lackowski (FESS). Photo: Reidar Hahn

This weekend, members of the Mu2e collaboration dug their shovels into the ground of Fermilab’s Muon Campus for the experiment that will search for the direct conversion of a muon into an electron in the hunt for new physics.

For decades, the Standard Model has stood as the best explanation of the subatomic world, describing the properties of the basic building blocks of matter and the forces that govern them. However, challenges remain, including that of unifying gravity with the other fundamental forces or explaining the matter-antimatter asymmetry that allows our universe to exist. Physicists have since developed new models, and detecting the direct conversion of a muon to an electron would provide evidence for many of these alternative theories.

“There’s a real possibility that we’ll see a signal because so many theories beyond the Standard Model naturally allow muon-to-electron conversion,” said Jim Miller, a co-spokesperson for Mu2e. “It’ll also be exciting if we don’t see anything, since it will greatly constrain the parameters of these models.”

Muons and electrons are two different flavors in the charged-lepton family. Muons are 200 times more massive than electrons and decay quickly into lighter particles, while electrons are stable and live forever. Most of the time, a muon decays into an electron and two neutrinos, but physicists have reason to believe that once in a blue moon, muons will convert directly into an electron without releasing any neutrinos. This is physics beyond the Standard Model.

Under the Standard Model, the muon-to-electron direct conversion happens too rarely to ever observe. In more sophisticated models, however, this occurs just frequently enough for an extremely sensitive machine to detect.

The Mu2e detector, when complete, will be the instrument to do this. The 92-foot-long apparatus will have three sections, each with its own superconducting magnet. Its unique S-shape was designed to capture as many slow muons as possible with an aluminum target. The direct conversion of a muon to an electron in an aluminum nucleus would release exactly 105 million electronvolts of energy, which means that if it occurs, the signal in the detector will be unmistakable. Scientists expect Mu2e to be 10,000 times more sensitive than previous attempts to see this process.

Construction will now begin on a new experimental hall for Mu2e. This hall will eventually house the detector and the infrastructure needed to conduct the experiment, such as the cryogenic systems to cool the superconducting magnets and the power systems to keep the machine running.

“What’s nice about the groundbreaking is that it becomes a real thing. It’s a long haul, but we’ll get there eventually, and this is a start,” said Julie Whitmore, deputy project manager for Mu2e.

The detector hall will be complete in late 2016. The experiment, funded mainly by the Department of Energy Office of Science, is expected to begin in 2020 and run for three years until peak sensitivity is reached.

“This is a project that will be moving along for many years. It won’t just be one shot,” said Stefano Miscetti, the leader of the Italian INFN group, Mu2e’s largest international collaborator. “If we observe something, we will want to measure it better. If we don’t, we will want to increase the sensitivity.”

Physicists around the world are working to extend the frontiers of the Standard Model. One hundred seventy-eight people from 31 institutions are coming together for Mu2e to make a significant impact on this venture.

“We’re sensitive to the same new physics that scientists are searching for at the Large Hadron Collider, we just look for it in a complementary way,” said Ron Ray, Mu2e project manager. “Even if the LHC doesn’t see new physics, we could see new physics here.”

—Diana Kwon

See a two-minute video on the ceremony

Tags: BSM Physics, Fermilab, Mu2e, muons
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Detecting something with nothing

Tuesday, March 3rd, 2015

Fermilab

This article appeared in Fermilab Today on March 3, 2015.

From left: Jason Bono (Rice University), Dan Ambrose (University of Minnesota) and Richie Bonventre (Lawrence Berkeley National Laboratory) work on the Mu2e straw chamber tracker unit at Lab 3. Photo: Reidar Hahn

Researchers are one step closer to finding new physics with the completion of a harp-shaped prototype detector element for the Mu2e experiment.

Mu2e will look for the conversion of a muon to only an electron (with no other particles emitted) — something predicted but never before seen. This experiment will help scientists better understand how these heavy cousins of the electron decay. A successful sighting would bring us nearer to a unifying theory of the four forces of nature.

The experiment will be 10,000 times as sensitive as other experiments looking for this conversion, and a crucial part is the detector that will track the whizzing electrons. Researchers want to find one whose sole signature is its energy of 105 MeV, indicating that it is the product of the elusive muon decay.

In order to measure the electron, scientists track the helical path it takes through the detector. But there’s a catch. Every interaction with detector material skews the path of the electron slightly, disturbing the measurement. The challenge for Mu2e designers is thus to make a detector with as little material as possible, says Mu2e scientist Vadim Rusu.

“You want to detect the electron with nothing — and this is as close to nothing as we can get,” he said.

So how to detect the invisible using as little as possible? That’s where the Mu2e tracker design comes in. Panels made of thin straws of metalized Mylar, each only 15 microns thick, will sit inside a cylindrical magnet. Rusu says that these are the thinnest straws that people have ever used in a particle physics experiment.

These straws, filled with a combination of argon and carbon dioxide gas and threaded with a thin wire, will wait in vacuum for the electrons. Circuit boards placed on both ends of the straws will gather the electrical signal produced when electrons hit the gas inside the straw. Scientists will measure the arrival times at each end of the wire to help accurately plot the electron’s overall trajectory.

“This is another tricky thing that very few have attempted in the past,” Rusu said.

The group working on the Mu2e tracker electronics have also created the tiny, low-power circuit boards that will sit at the end of each straw. With limited space to run cooling lines, necessary features that whisk away heat that would otherwise sit in the vacuum, the electronics needed to be as cool and small as possible.

“We actually spent a lot of time designing very low-power electronics,” Rusu said.

This first prototype, which researchers began putting together in October, gives scientists a chance to work out kinks, improve design and assembly procedures, and develop the necessary components.

One lesson already learned? Machining curved metal with elongated holes that can properly hold the straws is difficult and expensive. The solution? Using 3-D printing to make a high-tech, transparent plastic version instead.

Researchers also came up with a system to properly stretch the straws into place. While running a current through the straw, they use a magnet to pluck the straw — just like strumming a guitar string — and measure the vibration. This lets them set the proper tension that will keep the straw straight throughout the lifetime of the experiment.

Although the first prototype of the tracker is complete, scientists are already hard at work on a second version (using the 3D-printed plastic), which should be ready in June or July. The prototype will then be tested for leaks and to see if the electronics pick up and transmit signals properly.

A recent review of Mu2e went well, and Rusu expects work on the tracker construction to begin in 2016.

—Lauren Biron

Tags: detector R&D, Fermilab, Mu2e
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Mu2e attracts magnet experts

Wednesday, December 18th, 2013

Fermilab

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

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

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

“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

Tags: Fermilab, Mu2e, R&D
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Fermilab planning a busy 2012

Tuesday, January 3rd, 2012

Fermilab

This column by Fermilab Director Pier Oddone first appeared in Fermilab Today Jan. 3 .

We have a mountain of exciting work coming our way!

In accelerator operations, we need to give enough neutrinos to MINERvA to complete their low-energy run, enough anti-neutrinos to MiniBooNE to complete their run and enough neutrinos to MINOS to enable their independent neutrino velocity measurement that will follow up on last year’s OPERA results. We need to provide test beams to several technology development projects and overcome setbacks due to an aging infrastructure to deliver beam to the SeaQuest nuclear physics experiment. And we need to do all of this in the first few months of the year before a year-long shutdown starts. During the shutdown, we will modify the accelerator complex for the NOvA era and begin the campaign to double the number of protons from the Booster to deliver simultaneous beams to various experiments.

In parallel with accelerator modifications, we will push forward on many new experiments. The NOvA detector is in full construction mode, and we face challenges in the very large number of detector elements and large mechanical systems. Any project of this scale requires a huge effort to achieve the full promise of its design. We have the resources in our FY2012 budget to make a lot of progress toward MicroBooNE, Mu2e and LBNE. We will continue to work with DOE to advance Muon g-2. All these experiments are at an important stage in their development and need to be firmly established this year.

At the Cosmic Frontier, we will commission and start operation of the Dark Energy Survey at the Blanco Telescope in Chile, where the camera has arrived and is being tested. In the dark matter arena we will commission and operate the 60 kg COUPP detector at Canada’s SNOLAB and continue the run of the CDMS 15 kg detector in the Soudan Mine while carrying out R&D on future projects. We continue to have a major role in the operation of the Pierre Auger cosmic-ray observatory. In addition we should complete the first phase of the Fermilab Holometer, which will study the properties of space-time at the Planck scale.

At the Energy Frontier, we play a major role in the LHC detector operations and analysis. It should be a fabulously exciting year at the LHC as we push on the hints that we already see in the data.

Beyond construction and operation of facilities we continue our R&D efforts on the superconducting RF technology necessary for Project X and other future accelerators. We will be building the Illinois Accelerator Research Center and moving forward to connect our advanced accelerator program with industry and universities. Our rich program on theory, computation and detector technology will continue to support our laboratory and the particle physics community.

If we accomplish all that is ahead of us for 2012, it will be a year to remember and celebrate when we hit New Year’s Day 2013!

Tags: CDMS, CMS, cosmic rays, COUPP, Dark Energy Camera, Dark Energy Survey, dark matter, Energy Frontier, faster-than-light neutrinos, IARC, Intensity Frontier, Large Hadron Collider, LHC, MicroBooNe, Minerva, MINOS, Mu2e, neutrinos, NOvA, nuclear physics, Pier Auger Observatory, Project X, SeaQuest
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Mu2e passes milestone for challenging magnets

Monday, June 20th, 2011

Fermilab

This column by Mike Lamm, head of Fermilab’s Magnet Systems Department and Mu2e Level 2 Manager for Solenoids, first appeared in Fermilab Today May 25.

For the past 18 months, the Technical Division magnet program has been working on the development of several complex magnets for Mu2e (pronounced mew-2-e), one of the flagship experiments of Fermilab’s Intensity Frontier program. A few weeks ago, we achieved an important milestone when our detailed, conceptual design for the Mu2e magnets passed a three-day Director’s Technical Design Review of the entire project.

The Mu2e experiment will provide a strong test for beyond the Standard Model theories. Mu2e will look for the predicted but not-yet-observed direct conversion of a muon into an electron, a process known as charged lepton flavor violation. We know that all quarks can change flavor, such as a charm quark turning into an up quark, and we have recently learned that leptons without charge can change flavor too, such as a muon neutrino transforming into an electron neutrino. Hence we suspect that charged leptons such as muons might be able to likewise change flavor by directly converting into an electron. If they do, it will be a very rare process, and its discovery will require a special beamline and particle detector.

The Mu2e experiment will smash an intense beam of protons from Fermilab’s Booster accelerator into a gold target to produce lots of low-energy muons. A magnet known as the production solenoid will slow and collect these particles (see graphic). A transport solenoid will guide the muons through the S-shaped chicane that weeds out unwanted particles. Then the muons will be captured in an aluminum target. If and when a muon converts to an electron within the target, an electron detector within a detector solenoid will identify the emerging electron.

The production solenoid and detector solenoid resemble the superconducting solenoid magnets currently used in Tevatron and LHC experiments, but with additional requirements. The production solenoid must achieve 5 Tesla, or 100,000 times the earth’s magnetic field–the highest central magnetic field of any solenoid in particle physics. Its coils will experience 170 tons of force during operation, or the weight of four fully loaded 18-wheeler trucks. The detector solenoid will be comparable in diameter to the massive ATLAS central solenoid at the LHC, but will be longer, with a total length of more than 11 meters. It will store about the same amount of energy as the ATLAS solenoid, but will feature a more uniform magnetic field.

The transport solenoid will be like nothing else ever built. Because of its complex S-shape its superconducting coils will experience strong forces and torques that will pull in opposite directions when the adjacent coils are forced to power down during an operational hiccup known as a quench. This made its design very challenging.

With the detailed, conceptual design of the Mu2e magnets approved and almost complete, we are moving one step closer to building this experiment, and one step closer to a better understanding of our universe.

Related information:

*Mu2e: A little background (the nasty kind)

*The Mu2e Experiment: You Ordered What?

*Two Things Today

*The Quantum Mechanical Short-cut Through the Woods

Tags: Intensity Frontier, Mu2e
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Mu2e: A little background (the nasty kind)

Tuesday, April 26th, 2011

Fermilab

In experimental particle physics, the term “background” refers to events that can be easily confused for signal. In my last post , I introduced the Mu2e experiment and pointed out that this experiment needs a huge amount of muons (1 million trillion, 10¹⁸, or more) and hopes to be sensitive to even one muon decaying directly into an electron. To achieve such a single-event sensitivity the sources of backgrounds must be minimized and/or understood extremely well.

So, what is so difficult about that? Mu2e must have a striking experimental signature that is extremely hard to fake, right? Not exactly! The signal for the Mu2e experiment is just a single electron! Hmmm… That sounds like it could be a problem because every ordinary atom making up the experiment, the building housing the experiment and planet Earth that it sits on is made up of electrons!

The figure shows the muon-electron conversion energy distribution in light green and the energy distribution for electrons from one of the backgrounds in red. The signal energy is spread out due to the limited resolution of the Mu2e detector (not all of the signal events are measured to have the exact energy produced in the decay). The source of the background shown in red is from muons that decay in orbit (DIO) into an electron and neutrinos. This decay is allowed in the Standard Model. Because of the extra neutrinos produced in the final state, the electron carries less energy than the signal events where the muon decays only to electrons since no neutrinos are involved to take away some of the energy.

So, let’s state the problem again: the Mu2e experiment wants to stop 10¹⁸ muons on a target nucleus, and then be sensitive to even one event in which the muon decays directly into an electron. It isn’t easy! In fact, the experiment is carefully designed to minimize all potential sources of background events.

Luckily, the electrons produced from the direct muon-to-electron conversion are special in that their energy will always have the same value 105 megaelectron volts, or 105 MeV. This is an important point, because now, assuming that we can measure the energy of the electron well, our background has been reduced from “all electrons” to “electrons that have an energy close to 105 MeV” (see the figure at right). In the case of the Mu2e experiment, this means that we can reduce our total background to less than one event expected over the total running time of the experiment!

Taking this into account, it is clear that the amount of background will depend on how well the experiment can measure the energy of the 105 MeV electron. In other words, the sensitivity of the experiment depends critically on its ability to resolve the energy of an electron.

Future posts will include a series of “tricks” used by the experiment to control each of the major background sources.

— Craig Group

Tags: background, Intensity Frontier, Mu2e
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The Mu2e Experiment: You Ordered What?

Wednesday, February 23rd, 2011

Fermilab

This first Mu2e blog is designed to serve as an introduction to the purpose of the experiment. Stay tuned to Quantum Diaries for future Mu2e posts regarding some of the more subtle aspects of this unique experiment.

The layout of the Mu2e experiment. Muons are produced from a proton beam hitting a target and captured using magnetic fields. They are then transferred down the s-shaped transfer line to the stopping target . Stopped muons will decay, and the resulting electron will be studied using the particle detectors. Credit: symmetry magazine/Sandbox Studio

When the muon — a heavy version of the electron — was discovered, Isidor Rabi famously asked, “Who ordered that?”

Well, the Mu2e experiment at Fermilab would now like to place its order for 10²⁰, or 100 trillion, of these interesting particles. To put this staggering number in context, the Mu2e experiment needs almost as many muons as there are grains of sand on Earth.

Since the time of its discovery, scientists have questioned why the muon wouldn’t decay directly into an electron and a photon. It seems like a natural decay if the muon is just a heavy version of the electron. However, this decay has never been observed.

Similar to the decay, it may be possible for a muon to convert directly into an electron in the presence of a nucleus (the nucleus is required to conserve momentum and energy). Experimental limits suggest that if this occurs at all, it must occur for less than one out of 10 ¹³, or 10 billion, muons. The Mu2e experiment needs so many muons because it plans to improve on the sensitivity of previous experiments to this so called muon-to-electron conversion by four orders of magnitude. That is, the goal of the first two-year run of the experiment is to be sensitive to this process even if only one muon out of 10 ¹⁷, or 100 billiard. converts into an electron in this way. A plan for future experimental runs may even improve this by two more orders of magnitude.

Can’t wait for the next blog? Then check out these sites for more information:

Mu2e experiment website
Recent Mu2e article in symmetry magazine
Fact sheet on Mu2e

— Craig Group

Tags: flavor physics, Intensity Frontier, Mu2e, rare decay
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Posts Tagged ‘Mu2e’

*Mu2e: A little background (the nasty kind)

*The Mu2e Experiment: You Ordered What?

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