## Latest Posts

### The dawn of DUNE

Wednesday, March 25th, 2015

This article appeared in symmetry on March 25, 2015.

A powerful planned neutrino experiment gains new members, new leaders and a new name. Image: Fermilab

The neutrino experiment formerly known as LBNE has transformed. Since January, its collaboration has gained about 50 new member institutions, elected two new spokespersons and chosen a new name: Deep Underground Neutrino Experiment, or DUNE.

The proposed experiment will be the most powerful tool in the world for studying hard-to-catch particles called neutrinos. It will span 800 miles. It will start with a near detector and an intense beam of neutrinos produced at Fermi National Accelerator Laboratory in Illinois. It will end with a 10-kiloton far detector located underground in a laboratory at the Sanford Underground Research Facility in South Dakota. The distance between the two detectors will allow scientists to study how neutrinos change as they zip at close to the speed of light straight through the Earth.

“This will be the flagship experiment for particle physics hosted in the US,” says Jim Siegrist, associate director of high-energy physics for the US Department of Energy’s Office of Science. “It’s an exciting time for neutrino science and particle physics generally.”

In 2014, the Particle Physics Project Prioritization Panel identified the experiment as a top priority for US particle physics. At the same time, it recommended the collaboration take a few steps back and invite more international participation in the planning process.

Physicist Sergio Bertolucci, director of research and scientific computing at CERN, took the helm of an executive board put together to expand the collaboration and organize the election of new spokespersons.

DUNE now includes scientists from 148 institutions in 23 countries. It will be the first large international project hosted by the US to be jointly overseen by outside agencies.

This month, the collaboration elected two new spokespersons: André Rubbia, a professor of physics at ETH Zurich, and Mark Thomson, a professor of physics at the University of Cambridge. One will serve as spokesperson for two years and the other for three to provide continuity in leadership.

Rubbia got started with neutrino research as a member of the NOMAD experiment at CERN in the ’90s. More recently he was a part of LAGUNA-LBNO, a collaboration that was working toward a long-baseline experiment in Europe. Thomson has a long-term involvement in US-based underground and neutrino physics. He is the DUNE principle investigator for the UK.

Scientists are coming together to study neutrinos, rarely interacting particles that constantly stream through the Earth but are not well understood. They come in three types and oscillate, or change from type to type, as they travel long distances. They have tiny, unexplained masses. Neutrinos could hold clues about how the universe began and why matter greatly outnumbers antimatter, allowing us to exist.

“The science is what drives us,” Rubbia says. “We’re at the point where the next generation of experiments is going to address the mystery of neutrino oscillations. It’s a unique moment.”

Scientists hope to begin installation of the DUNE far detector by 2021. “Everybody involved is pushing hard to see this project happen as soon as possible,” Thomson says.

Jennifer Huber and Kathryn Jepsen

Image: Fermilab

### Vote LUX, and give an underdog a chance

Wednesday, March 25th, 2015

I’ve had a busy few weeks after getting back from America, so apologies for the lack of blogging! Some things I’ve been up to:
– Presenting my work on LUX to MPs at the Houses of Parliament for the SET for Britain competition. No prizes, but lots of interesting questions from MPs, for example: “and what can you do with dark matter once you find it?”. I think he was looking for monetary gain, so perhaps I should have claimed dark matter will be the zero-carbon fuel of the future!
– Supplementing my lowly salary by marking an enormous pile of undergraduate problem sheets and by participating in paid eye-tracking studies for both the UCL psychology department and a marketing company
– The usual work on analysing LUX data and trying to improve our sensitivity to low mass dark matter.
And on Saturday, I will be on a panel of “experts” (how this has happened I don’t know) giving a talk as part of the UCL Your Universe festival. The discussion is aptly titled “Light into the Dark: Mystery of the Invisible Universe”, and if you’re in London and interested in this sort of thing, you should come along. Free tickets are available here.

I will hopefully be back to posting more regularly now, but first, a bit of promotion!

Symmetry Magazine are running a competition to find “which physics machine will reign supreme” and you can vote right here.

Physics Madness: Symmetry Magazine’s tournament to find the champion physics experiment

The first round matches LUX with the LHC, and considering we are a collaboration of just over 100 (compared to CERN’s thousands of scientists) with nothing like the media coverage the LHC gets, we’re feeling like a bit of an underdog.
But you can’t just vote for us because we’re an underdog, so here are some reasons you should #voteLUX:

-For spin-dependent WIMP-nucleon scattering for WIMPs above ~8GeV, LUX is 10,000x more sensitive than the LHC (see figure below).
-LUX cost millions of dollars, the LHC cost billions.
-It’s possible to have an understanding of how LUX works in its entirety. The LHC is too big and has too many detectors for that!
-The LHC is 175m underground. LUX is 1,478m underground, over 8x deeper, and so is much better shielded from cosmic rays.
-The LHC has encountered problems both times it has tried to start up. LUX is running smoothly right now!
-I actually feel kind of bad now, because I like the LHC, so I will stop.

Dark matter sensitivity limits, comparing LHC results to LUX in red. The x axis is the mass of the dark matter particle, and the y axis is its interaction probability. The smaller this number, the greater the sensitivity.

Anyway, if you fancy giving the world’s most sensitive dark matter detector a hint of a chance in it’s battle against the behemoth LHC, vote LUX. Let’s beat the system!

### Expanding the cosmic search

Friday, March 20th, 2015

This article appeared in Fermilab Today on March 20, 2015.

The South Pole Telescope scans the skies during a South Pole winter. Photo: Jason Gallicchio, University of Chicago

Down at the South Pole, where temperatures drop below negative 100 degrees Fahrenheit and darkness blankets the land for six months at a time, the South Pole Telescope (SPT) searches the skies for answers to the mysteries of our universe.

This mighty scavenger is about to get a major upgrade — a new camera that will help scientists further understand neutrinos, the ghost-like particles without electric charge that rarely interact with matter.

The 10-meter SPT is the largest telescope ever to make its way to the South Pole. It stands atop a two-mile thick plateau of ice, mapping the cosmic microwave background (CMB), the light left over from the big bang. Astrophysicists use these observations to understand the composition and evolution of the universe, all the way back to the first fraction of a second after the big bang, when scientists believe the universe quickly expanded during a period called inflation.

One of the goals of the SPT is to determine the masses of the neutrinos, which were produced in great abundance soon after the big bang. Though nearly massless, because neutrinos exist in huge numbers, they contribute to the total mass of the universe and affect its expansion. By mapping out the mass density of the universe through measurements of CMB lensing, the bending of light caused by immense objects such as large galaxies, astrophysicists are trying to determine the masses of these elusive particles.

A wafer of detectors for the SPT-3G camera undergoes inspection at Fermilab. Photo: Bradford Benson, University of Chicago

To conduct these extremely precise measurements, scientists are installing a bigger, more sensitive camera on the telescope. This new camera, SPT-3G, will be four times heavier and have a factor of about 10 more detectors than the current camera. Its higher level of sensitivity will allow researchers to make extremely precise measurements of the CMB that will hopefully make it possible to cosmologically detect neutrino mass.

This photo shows an up-close look at a single SPT-3G detector. Photo: Volodymyr Yefremenko, Argonne National Laboratory

“In the next several years, we should be able to get to the sensitivity level where we can measure the number of neutrinos and derive their mass, which will tell us how they contribute to the overall density of the universe,” explained Bradford Benson, the head of the CMB Group at Fermilab. “This measurement will also enable even more sensitive constraints on inflation and has the potential to measure the energy scale of the associated physics that caused it.”

SPT-3G is being completed by a collaboration of scientists spanning the DOE national laboratories, including Fermilab and Argonne, and universities including the University of Chicago and University of California, Berkeley. The national laboratories provide the resources needed for the bigger camera and larger detector array while the universities bring years of expertise in CMB research.

“The national labs are getting involved because we need to scale up our infrastructure to support the big experiments the field needs for the next generation of science goals,” Benson said. Fermilab’s main role is the initial construction and assembly of the camera, as well as its integration with the detectors. This upgrade is being supported mainly by the Department of Energy and the National Science Foundation, which also supports the operations of the experiment at the South Pole.

Once the camera is complete, scientists will bring it to the South Pole, where conditions are optimal for these experiments. The extreme cold prevents the air from holding much water vapor, which can absorb microwave signals, and the sun, another source of microwaves, does not rise between March and September.

The South Pole is accessible only for about three months during the year, starting in November. This fall, about 20 to 30 scientists will head down to the South Pole to assemble the camera on the telescope and make sure everything works before leaving in mid-February. Once installed, scientists will use it to observe the sky over four years.

“For every project I’ve worked on, it’s that beginning — when everyone is so excited not knowing what we’re going to find, then seeing things you’ve been dreaming about start to show up on the computer screen in front of you — that I find really exciting,” said University of Chicago’s John Carlstrom, the principal investigator for the SPT-3G project.

Diana Kwon

### Ramping up to Run 2

Thursday, March 19th, 2015

When I have taught introductory electricity and magnetism for engineers and physics majors at the University of Nebraska-Lincoln, I have used a textbook by Young and Freedman. (Wow, look at the price of that book! But that’s a topic for another day.) The first page of Chapter 28, “Sources of Magnetic Field,” features this photo:

It shows the cryostat that contains the solenoid magnet for the Compact Muon Solenoid experiment. Yes, “solenoid” is part of the experiment’s name, as it is a key element in the design of the detector. There is no other magnet like it in the world. It can produce a 4 Tesla magnetic field, 100,000 times greater than that of the earth. (We actually run at 3.8 Tesla.) Charged particles that move through a magnetic field take curved paths, and the stronger the field, the stronger the curvature. The more the path curves, the more accurately we can measure it, and thus the more accurately we can measure the momentum of the particle.

The magnet is superconducting; it is kept inside a cryostat that is full of liquid helium. With a diameter of seven meters, it is the largest superconducting magnet ever built. When in its superconducting state, the magnet wire carries more than 18,000 amperes of current, and the energy stored is about 2.3 gigajoules, enough energy to melt 18 tons of gold. Should the temperature inadvertently rise and the magnet become normal conducting, all of that energy needs to go somewhere; there are some impressively large copper conduits that can carry the current to the surface and send it safely to ground. (Thanks to the CMS web pages for some of these fun facts.)

With the start of the LHC run just weeks away, CMS has turned the magnet back on by slowly ramping up the current. Here’s what that looked like today:

You can see that they took a break for lunch! It is only the second time since the shutdown started two years ago that the magnet has been ramped back up, and now we’re pretty much going to keep it on for at least the rest of the year. From the experiment’s perspective, the long shutdown is now over, and the run is beginning. CMS is now prepared to start recording cosmic rays in this configuration, as a way of exercising the detector and using the observed muon to improve our knowledge of the alignment of detector components. This is a very important milestone for the experiment as we prepare for operating the LHC at the highest collision energies ever achieved in the laboratory!

### On Being an Artwork

Thursday, March 19th, 2015

Back when we were discussing Will Self’s impression of CERN as a place where scientists had no interest in the important philosophical questions, I commented that part of the trouble was Self’s expectation that scientists who were expecting to give him a technical tour should be prepared to have an ad hoc philosophical discussion instead. I also mentioned that many physicists can and will give interviews on broader topics. What I didn’t mention is that I included myself, because I had already done an interview in 2014 on the “existential” boundaries of physics knowledge. I didn’t know at the time that that interview had already been made part of an art installation! I ran across the installation by chance recently, and I think it’s worth taking a close look at because it provides a positive example of substantive engagement between art, philosophy, and science.

The installation is “sub specie aeternitatis”, by Rosalind McLachlan. It is described in a review for Axisweb by Matthew Hearn as “seek[ing] greater understanding not through belief in the knowable, but in asking scientists to address the limitations of their field and forcing them to consider the ‘existential horror’ – the problems of our existence in terms of what we can’t know.” It features five CERN physicists talking all at once on separate screens about questions that physics can’t necessarily answer. If I remember correctly, it looks like mine was “What happened before the Big Bang?”

I didn’t get to see the exhibit itself, but the review makes it clear that the installation went far beyond simply showing video of the interviewees. The artist made conscious decisions about how to weave our words and surroundings together:

Whilst at any one moment only a single voice plays, thinking aloud – struggling to find meaning – collectively all five characters appear to be working together, evolving a visual language of gesture and animated body movement, grasping to find some shared form of resolution. CERN has been celebrated for the way international communities collaborate, put individual agendas aside, and share knowledge and understanding, and the visual simultaneity within McLachlan’s installation captures this collegiate approach.

The piece thus presents the core values of international collaborative science in a novel way, beyond the mere words scientists usually use to explain it. But it isn’t a new allegory divorced from actual scientists at CERN and our work: it still uses our own words, mannerisms, and office whiteboards to build the impression. What a wonderful example of how art can add new dimensions to communicating about science!

Looking at my part of an excerpt from the installation video, it’s clear why I’m in it. Not so much because of what I’m saying – a lot of it is explained better on Sean Carroll’s blog, even if I do disagree with him sometimes on philosophical interpretations. But because of how I’m saying it: slowly, with long deliberate pauses that allow the other screens to speak and give the impression that I’m working things out as I go along. What I was really doing is working how best to communicate my ideas, but this installation isn’t replicating life as literally as a documentary would. It does replicate how some physicists think about science and philosophy, and how we work together, and I think that’s remarkable.

### Video contest: Rock the LHC!

Tuesday, March 17th, 2015

Do you think the Large Hadron Collider rocks? I sure do, and as the collider rocks back to life in the coming weeks (more on that soon), you can celebrate by entering the Rock the LHC video contest. It’s simple: you make a short video about why you are excited about research at the LHC, and submit it to a panel of physicists and communication experts. The producer of the best video will win an all-expenses paid trip for two to Fermilab in Batavia, IL, the premier particle physics laboratory in the United States, for a VIP tour. What a great way to celebrate the restart of the world’s most powerful particle collider!

This contest is funded by the University of Notre Dame, and please note the rules — you must be over 18 and a legal U.S. resident currently residing in the 50 states or the District of Columbia to enter. The deadline for entries is May 31.

As we get ready for the collider run of a lifetime, let’s see how creative you can be about the exciting science that is ahead of us!

### Einstein’s most famous equation

Friday, March 13th, 2015

This article appeared in symmetry on March 12, 2015.

You’ve heard of Einstein’s E=mc2, but what does it mean?

With Einstein’s birthday just around the corner on March 14 (which also happens to be Pi Day), it seems appropriate to take a fresh look at one of his biggest accomplishments with a short video.

In 1905, Einstein published four papers that radically changed how we look at the world around us. Dubbed Einstein’s “Annus Mirabilis,” or “Year of Wonders,” it gave us revolutionary new ideas about light, atoms and how your frame of reference makes a big difference in your perception.

It was Einstein’s final paper that year that really took the (birthday) cake. In it, he gave us a deceptively simple idea—that mass and energy were equivalent. He even summed it up for us with the tiny equation E=mc2*.

However, while appearing simple, the implications of E=mc2 are huge and far-reaching. To find out why, sit back, enjoy some birthday cake (or pie, depending on how you’re celebrating), and watch the video!

*Although we are most familiar with E=mc2, Einstein didn’t quite say it that way in the original paper. It was actually in the form of a sentence in German: “If a body gives off the energy L in the form of radiation, its mass diminishes by L/V2.”

Chris Smith

### Scientists find rare dwarf satellite galaxy candidates in Dark Energy Survey data

Tuesday, March 10th, 2015

This Fermilab press release came out on March 10, 2015.

Scientists on two continents have independently discovered a set of celestial objects that seem to belong to the rare category of dwarf satellite galaxies orbiting our home galaxy, the Milky Way.

Dwarf galaxies are the smallest known galaxies, and they could hold the key to understanding dark matter and the process by which larger galaxies form.

A team of researchers with the Dark Energy Survey, headquartered at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, and an independent group from the University of Cambridge jointly announced their findings today. Both teams used data taken during the first year of the Dark Energy Survey, all of which is publicly available, to carry out their analysis.

“The large dark matter content of Milky Way satellite galaxies makes this a significant result for both astronomy and physics,” said Alex Drlica-Wagner of Fermilab, one of the leaders of the Dark Energy Survey analysis.

Satellite galaxies are small celestial objects that orbit larger galaxies, such as our own Milky Way. Dwarf galaxies can be found with fewer than 100 stars and are remarkably faint and difficult to spot. (By contrast, the Milky Way, an average-sized galaxy, contains billions of stars.)

These newly discovered objects are a billion times dimmer than the Milky Way and a million times less massive. The closest of them is about 100,000 light-years away.

“The discovery of so many satellites in such a small area of the sky was completely unexpected,” said Cambridge’s Institute of Astronomy’s Sergey Koposov, the Cambridge study’s lead author. “I could not believe my eyes.”

Scientists have previously found more than two dozen of these satellite galaxies around our Milky Way. About half of them were discovered in 2005 and 2006 by the Sloan Digital Sky Survey, the precursor to the Dark Energy Survey. After that initial explosion of discoveries, the rate fell to a trickle and dropped off entirely over the past five years.

The Dark Energy Survey is looking at a new portion of the southern hemisphere, covering a different area of sky than the Sloan Digital Sky Survey. The galaxies announced today were discovered in a search of only the first of the planned five years of Dark Energy Survey data, covering roughly one-third of the portion of sky that DES will study. Scientists expect that the full Dark Energy Survey will find up to 30 of these satellite galaxies within its area of study.

This illustration maps out the previously discovered dwarf satellite galaxies (in blue) and the newly discovered candidates (in red) as they sit outside the Milky Way. Image: Yao-Yuan Mao, Ralf Kaehler, Risa Wechsler (KIPAC/SLAC).

Atlas image obtained as part of the Two Micron All Sky Survey (2MASS), a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

While more analysis is required to confirm any of the observed celestial objects as satellite galaxies, researchers note their size, low surface brightness and significant distance from the center of the Milky Way as evidence that they are excellent candidates. Further tests are ongoing, and data collected during the second year of the Dark Energy Survey could yield more of these potential dwarf galaxies to study.

Newly discovered galaxies would also present scientists with more opportunities to search for signatures of dark matter. Dwarf satellite galaxies are dark matter-dominated, meaning they have much more mass in unseen matter than in stars. The nature of this dark matter remains unknown but might consist of particles that annihilate each other and release gamma rays. Because dwarf galaxies do not host other gamma ray sources, they make ideal laboratories to search for signs of dark matter annihilation. Scientists are confident that further study of these objects will lead to even more sensitive searches for dark matter.

In a separate result also announced today, the Large Area Telescope Collaboration for NASA’s Fermi Gamma-Ray Telescope mission reported that they did not see any significant excess of gamma ray emission associated with the new Dark Energy Survey objects. This result demonstrates that new discoveries from optical telescopes can be quickly translated into tests of fundamental physics.

“We did not detect significant emission with the LAT, but the dwarf galaxies that DES has and will discover are extremely important targets for the dark matter search,” said Peter Michelson, spokesperson for the LAT collaboration. “If not leading to an identification of particle dark matter, they will certainly be useful to constrain its properties.”

The Dark Energy Survey is a five-year effort to photograph a large portion of the southern sky in unprecedented detail. Its primary instrument is the Dark Energy Camera, which – at 570 megapixels – is the most powerful digital camera in the world, able to see galaxies up to 8 billion light-years from Earth. Built and tested at Fermilab, the camera is now mounted on the 4-meter Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory in the Andes Mountains in Chile.

The survey’s five-year mission is to discover clues about the nature of dark energy, the mysterious force that makes up about 70 percent of all matter and energy in the universe. Scientists believe that dark energy may be the key to understanding why the expansion of the universe is accelerating.

“The Dark Energy Camera is a perfect instrument for discovering small satellite galaxies,” said Keith Bechtol of the Kavli Institute for Cosmological Physics at the University of Chicago, who helped lead the Dark Energy Survey analysis. “It has a very large field of view to quickly map the sky and great sensitivity, enabling us to look at very faint stars. These results show just how powerful the camera is and how significant the data it collects will be for many years to come.”

The Dark Energy Survey analysis is available here. The University of Cambridge analysis is available here.

The Dark Energy Survey is a collaboration of more than 300 scientists from 25 institutions in six countries. For more information about the survey, please visit the experiment’s website.

Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência e Tecnologia, the Deutsche Forschungsgemeinschaft and the collaborating institutions in the Dark Energy Survey. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2012-39559, ESP2013-48274, FPA2013-47986 and Centro de Excelencia Severo Ochoa SEV-2012-0234, some of which include ERDF funds from the European Union.

Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance, LLC. Visit Fermilab’s website at www.fnal.gov and follow us on Twitter at @Fermilab.

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 science.energy.gov .

The mission of the University of Cambridge is to contribute to society through the pursuit of education, learning and research at the highest international levels of excellence. To date, 90 affiliates of the university have won the Nobel Prize. Founded in 1209, the university comprises 31 autonomous colleges, which admit undergraduates and provide small-group tuition, and 150 departments, faculties and institutions. Cambridge is a global university. Its 19,000 student body includes 3,700 international students from 120 countries. Cambridge researchers collaborate with colleagues worldwide, and the university has established larger-scale partnerships in Asia, Africa and America. The university sits at the heart of one of the world’s largest technology clusters. The ‘Cambridge Phenomenon’ has created 1,500 hi-tech companies, 14 of them valued at over US$1 billion and two at over US$10 billion. Cambridge promotes the interface between academia and business and has a global reputation for innovation. www.cam.ac.uk .

### Detecting something with nothing

Tuesday, March 3rd, 2015

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

### 30 reasons why you shouldn’t be a particle physicist

Monday, March 2nd, 2015

(ATLAS)

## 2. They say “There’s nothing like the thrill of discovery”.

(ALICE Masterclass)

(CERN)

(CERN)

(CERN)

## 7. The machines are among the most complex in the world.

(Francois Becler)

(CERN)

## 9. They’re not even nice to look at.

(Michael Hoch, Maximilien Brice)

(CERN)

(CERN)

(CERN Courier)

(LHCb)

(Wikipedia)

(CERN)

(Sean Treacy)

(STFC)

(ATLAS)

(CERN)

## 30. Honestly, who would want to be a physicist?

(CMS)

References:

• http://www.atlas.ch/news/2008/first-beam-and-event.html
• http://opendata.cern.ch/collection/ALICE-Learning-Resources
• http://cds.cern.ch/record/1406060?ln=en
• http://cds.cern.ch/record/1459634
• http://cds.cern.ch/record/1459503?ln=en
• http://cds.cern.ch/record/1474902/files/
• https://cds.cern.ch/record/1643071/
• http://cds.cern.ch/record/1436153?ln=en