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Summer intern studies physics for self, family

Tuesday, September 16th, 2014

This article appeared in Fermilab Today on Sept. 16, 2014.

Summer intern Sheri Lopez, here with son Dominic, pursues her love of physics as a student at the University of New Mexico-Los Alamos. She spent this summer at Fermilab as a summer intern. Photo courtesy of Sheri Lopez

Summer intern Sheri Lopez, here with son Dominic, pursues her love of physics as a student at the University of New Mexico-Los Alamos. She spent this summer at Fermilab as a summer intern. Photo courtesy of Sheri Lopez

Dominic is two. He is obsessed with “Despicable Me” and choo-choos. His mom Sheri Lopez is 29, obsessed with physics, and always wanted to be an astronaut.

But while Dominic’s future is full of possibilities, his mom’s options are narrower. Lopez is a single mother and a sophomore at the University of New Mexico-Los Alamos, where she is double majoring in physics and mechanical engineering. Her future is focused on providing for her son, and that plan recently included 10 weeks spent at Fermilab for a Summer Undergraduate Laboratories Internship (SULI).

“Being at Fermilab was beautiful, and it really made me realize how much I love physics,” Lopez said. “On the other end of the spectrum, it made me realize that I have to think of my future in a tangible way.”

Instead of being an astronaut, now she plans on building the next generation of particle detectors. Lopez is reaching that goal by coupling her love of physics with practical trade skills such as coding, which she picked up at Fermilab as part of her research developing new ways to visualize data for the MINERvA neutrino experiment.

“The main goal of it was to try to make the data that the MINERvA project was getting a lot easier to read and more presentable for a web-based format,” Lopez said. Interactive, user-friendly data may be one way to generate interest in particle physics from a more diverse audience. Lopez had no previous coding experience but quickly realized at Fermilab that it would allow her to make a bigger difference in the field.

Dominic, meanwhile, spent the summer with his grandparents in New Mexico. That was hard, Lopez said, but she received a lot of support from Internship Program Administrator Tanja Waltrip.

“I was determined to not let her miss this opportunity, which she worked so hard to acquire,” Waltrip said. Waltrip coordinates support services for interns like Lopez in 11 different programs hosted by Fermilab.

Less than 10 percent of applicants were accepted into Fermilab’s summer program. SULI is funded by the U.S. Department of Energy, so many national labs host these internships, and applicants choose which labs to apply to.

“There was never a moment when anyone doubted or said I couldn’t do it,” Lopez said. Dominic doesn’t understand why his mom was gone this summer, but he made sure to give her the longest hug of her life when she came back. For her part, Lopez was happy to bring back a brighter future for her son.

Troy Rummler

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Neutrinos permeate Fermilab’s past, present and future

Monday, September 8th, 2014

This article appeared in Fermilab Today on Sept. 5, 2014.

This aerial view shows the Neutrino Area under construction in May 1971. The 15-foot bubble chamber, pictured on the left, would later be moved to the present-day location of Lab D.  Photo: Fermilab

This aerial view shows the Neutrino Area under construction in May 1971. The 15-foot bubble chamber, pictured on the left, would later be moved to the present-day location of Lab B. Photo: Fermilab

It was called Target Station C. One of three stations north of Wilson Hall at the end of beamlines extending from the Main Ring (later replaced by the Tevatron), Target Station C was assigned to experiments that would require high beam intensities for investigating neutrino interactions, according to a 1968 design report.

Within a few years, Target Station C was officially renamed the Neutrino Area. It was the first named fixed-target area and the first to be fully operational. Neutrinos and the Intensity Frontier had an early relationship with Fermilab. But why is it resurfacing now?

“The experimental program is driven by the current state of knowledge, and that’s always changing,” said Jeffrey Appel, a retired Fermilab physicist and assistant laboratory director who started research at the lab in 1972.

When Appel first arrived, there was intense interest in neutrinos because the weak force was poorly understood, and neutral currents were still a controversial idea. Fermilab joined forces with many institutions both in and outside the United States, and throughout the 1970s and early 1980s, neutrinos generated from protons in the Main Ring crashed through a 15-foot bubble chamber filled with super-heated liquid hydrogen. Other experiments running in parallel recorded neutrino interactions in iron and scintillator.

“The goal was to look for the W and Z produced in neutrino interactions,” said Appel. “So the priority for getting the beam up first and the priority for getting the detectors built and installed was on that program in those days.”

It turns out that the W and Z bosons are too massive to have been produced this way and had to wait to be discovered at colliding-beam experiments. As soon as the Tevatron was ready for colliding beams in 1985, the transition began at Fermilab from fixed-target areas to high-energy particle colliding.

More recent revelations have shown that neutrinos have mass. These findings have raised new questions that need answers. In 1988, plans were laid to add the Main Injector to the Fermilab campus, partly to boost the capabilities of the Tevatron, but also, according to one report, because “intense beams of neutral kaons and neutrinos would provide a unique facility for CP violation and neutrino oscillation experiments.”

Although neutrino research was a smaller fraction of the lab’s program during Tevatron operations, it was far from dormant. Two great accomplishments in neutrino research occurred in this time period: One was the most precise neutrino measurement of the strength of the weak interaction by the NuTeV experiment. The other was when the DONUT experiment achieved its goal of making the first direct observation of the tau neutrino in 2000.

“In the ’90s most evidence of neutrinos changing flavors was coming from natural sources. But this inspired a whole new generation of accelerator-based neutrino experiments,” said Deborah Harris, co-spokesperson for the MINERvA neutrino experiment. “That’s when Fermilab changed gears to make lower-energy but very intense neutrino beams that were uniquely suited for oscillation physics.”

In partnership with institutions around the globe, Fermilab began planning and building a suite of neutrino experiments. MiniBooNE and MINOS started running in the early 2000s and MINERvA started in 2010. MicroBooNE and NOvA are starting their runs this year.

Now the lab is working with other institutions to establish a Long-Baseline Neutrino Facility at the laboratory and advance its short-baseline neutrino research program. As Fermilab strengthens its international partnerships in all its neutrino experiments, it is also working to position itself as the home of the world’s forefront neutrino research.

“The combination of the completion of the Tevatron program and the new questions about neutrinos means that it’s an opportune time to redefine the focus of Fermilab,” Appel explained.

“Everybody says: ‘It’s not like the old days,’ and it’s always true,” Appel said. “Experiments are bigger and more expensive, but people are just as excited about what they’re doing.”

He added, “It’s different now but just as exciting, if not more so.”

Troy Rummler

Special thanks go to Fermilab archivists Valerie Higgins and Adrienne Kolb for helping navigate Fermilab’s many resources on early neutrino research at the laboratory.

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Do we live in a 2-D hologram?

Tuesday, August 26th, 2014

This Fermilab press release was published on Aug. 26, 2014.

A Fermilab scientist works on the laser beams at the heart of the Holometer experiment. The Holometer will use twin laser interferometers to test whether the universe is a 2-D hologram. Photo: Fermilab

A Fermilab scientist works on the laser beams at the heart of the Holometer experiment. The Holometer will use twin laser interferometers to test whether the universe is a 2-D hologram. Photo: Fermilab

A unique experiment at the U.S. Department of Energy’s Fermi National Accelerator Laboratory called the Holometer has started collecting data that will answer some mind-bending questions about our universe – including whether we live in a hologram.

Much like characters on a television show would not know that their seemingly 3-D world exists only on a 2-D screen, we could be clueless that our 3-D space is just an illusion. The information about everything in our universe could actually be encoded in tiny packets in two dimensions.

Get close enough to your TV screen and you’ll see pixels, small points of data that make a seamless image if you stand back. Scientists think that the universe’s information may be contained in the same way and that the natural “pixel size” of space is roughly 10 trillion trillion times smaller than an atom, a distance that physicists refer to as the Planck scale.

“We want to find out whether space-time is a quantum system just like matter is,” said Craig Hogan, director of Fermilab’s Center for Particle Astrophysics and the developer of the holographic noise theory. “If we see something, it will completely change ideas about space we’ve used for thousands of years.”

Quantum theory suggests that it is impossible to know both the exact location and the exact speed of subatomic particles. If space comes in 2-D bits with limited information about the precise location of objects, then space itself would fall under the same theory of uncertainty. The same way that matter continues to jiggle (as quantum waves) even when cooled to absolute zero, this digitized space should have built-in vibrations even in its lowest energy state.

Essentially, the experiment probes the limits of the universe’s ability to store information. If there is a set number of bits that tell you where something is, it eventually becomes impossible to find more specific information about the location – even in principle. The instrument testing these limits is Fermilab’s Holometer, or holographic interferometer, the most sensitive device ever created to measure the quantum jitter of space itself.

Now operating at full power, the Holometer uses a pair of interferometers placed close to one another. Each one sends a one-kilowatt laser beam (the equivalent of 200,000 laser pointers) at a beam splitter and down two perpendicular 40-meter arms. The light is then reflected back to the beam splitter where the two beams recombine, creating fluctuations in brightness if there is motion. Researchers analyze these fluctuations in the returning light to see if the beam splitter is moving in a certain way – being carried along on a jitter of space itself.

“Holographic noise” is expected to be present at all frequencies, but the scientists’ challenge is not to be fooled by other sources of vibrations. The Holometer is testing a frequency so high – millions of cycles per second – that motions of normal matter are not likely to cause problems. Rather, the dominant background noise is more often due to radio waves emitted by nearby electronics. The Holometer experiment is designed to identify and eliminate noise from such conventional sources.

“If we find a noise we can’t get rid of, we might be detecting something fundamental about nature – a noise that is intrinsic to space-time,” said Fermilab physicist Aaron Chou, lead scientist and project manager for the Holometer. “It’s an exciting moment for physics. A positive result will open a whole new avenue of questioning about how space works.”

The Holometer experiment, funded by the U.S. Department of Energy Office of Science and other sources, is expected to gather data over the coming year.

The Holometer team comprises 21 scientists and students from Fermilab, the Massachusetts Institute of Technology, the University of Chicago and the University of Michigan. For more information about the experiment, visit http://holometer.fnal.gov/.

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 @FermilabToday.

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.

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Dark Energy Survey kicks off second season cataloging the wonders of deep space

Monday, August 18th, 2014

This Fermilab press release came out on Aug. 18, 2014.

This image of the NGC 1398 galaxy was taken with the Dark Energy Camera. This galaxy lives in the Fornax cluster, roughly 65 million light-years from Earth. It is 135,000 light-years in diameter, just slightly larger than our own Milky Way galaxy, and contains more than 100 billion stars. Credit: Dark Energy Survey

This image of the NGC 1398 galaxy was taken with the Dark Energy Camera. This galaxy lives in the Fornax cluster, roughly 65 million light-years from Earth. It is 135,000 light-years in diameter, just slightly larger than our own Milky Way galaxy, and contains more than 100 billion stars. Credit: Dark Energy Survey

On Aug. 15, with its successful first season behind it, the Dark Energy Survey (DES) collaboration began its second year of mapping the southern sky in unprecedented detail. Using the Dark Energy Camera, a 570-megapixel imaging device built by the collaboration and mounted on the Victor M. Blanco Telescope in Chile, the survey’s five-year mission is to unravel the fundamental mystery of dark energy and its impact on our universe.

Along the way, the survey will take some of the most breathtaking pictures of the cosmos ever captured. The survey team has announced two ways the public can see the images from the first year.

Today, the Dark Energy Survey relaunched Dark Energy Detectives, its successful photo blog. Once every two weeks during the survey’s second season, a new image or video will be posted to www.darkenergydetectives.org, with an explanation provided by a scientist. During its first year, Dark Energy Detectives drew thousands of readers and followers, including more than 46,000 followers on its Tumblr site.

Starting on Sept. 1, the one-year anniversary of the start of the survey, the data collected by DES in its first season will become freely available to researchers worldwide. The data will be hosted by the National Optical Astronomy Observatory. The Blanco Telescope is hosted at the National Science Foundation’s Cerro Tololo Inter-American Observatory, the southern branch of NOAO.

In addition, the hundreds of thousands of individual images of the sky taken during the first season are being analyzed by thousands of computers at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, Fermi National Accelerator Laboratory (Fermilab), and Lawrence Berkeley National Laboratory. The processed data will also be released in coming months.

Scientists on the survey will use these images to unravel the secrets of dark energy, the mysterious substance that makes up 70 percent of the mass and energy of the universe. Scientists have theorized that dark energy works in opposition to gravity and is responsible for the accelerating expansion of the universe.

“The first season was a resounding success, and we’ve already captured reams of data that will improve our understanding of the cosmos,” said DES Director Josh Frieman of the U.S. Department of Energy’s Fermi National Accelerator Laboratory and the University of Chicago. “We’re very excited to get the second season under way and continue to probe the mystery of dark energy.”

While results on the survey’s probe of dark energy are still more than a year away, a number of scientific results have already been published based on data collected with the Dark Energy Camera.

The first scientific paper based on Dark Energy Survey data was published in May by a team led by Ohio State University’s Peter Melchior. Using data that the survey team acquired while putting the Dark Energy Camera through its paces, they used a technique called gravitational lensing to determine the masses of clusters of galaxies.

In June, Dark Energy Survey researchers from the University of Portsmouth and their colleagues discovered a rare superluminous supernova in a galaxy 7.8 billion light years away. A group of students from the University of Michigan discovered five new objects in the Kuiper Belt, a region in the outer reaches of our solar system, including one that takes over a thousand years to orbit the Sun.

In February, Dark Energy Survey scientists used the camera to track a potentially hazardous asteroid that approached Earth. The data was used to show that the newly discovered Apollo-class asteroid 2014 BE63 would pose no risk.

Several more results are expected in the coming months, said Gary Bernstein of the University of Pennsylvania, project scientist for the Dark Energy Survey.

The Dark Energy Camera was built and tested at Fermilab. The camera can see light from more than 100,000 galaxies up to 8 billion light-years away in each crystal-clear digital snapshot.

“The Dark Energy Camera has proven to be a tremendous tool, not only for the Dark Energy Survey, but also for other important observations conducted year-round,” said Tom Diehl of Fermilab, operations scientist for the Dark Energy Survey. “The data collected during the survey’s first year — and its next four — will greatly improve our understanding of the way our universe works.”

The Dark Energy Survey Collaboration comprises more than 300 researchers from 25 institutions in six countries. For more information, visit http://www.darkenergysurvey.org.

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 @FermilabToday.

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 National Optical Astronomy Observatory (NOAO) is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation.

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Latest video in Huffington Post’s Talk Nerdy to Me video series

Monday, August 11th, 2014

Watch Fermilab Deputy Director Joe Lykken in the latest entry in Huffington Post's "Talk Nerdy To Me" video series.

Watch Fermilab Deputy Director Joe Lykken in the latest entry in Huffington Post’s “Talk Nerdy To Me” video series.


What’s the smallest thing in the universe? Check out the latest entry in Huffington Post‘s Talk Nerdy to Me video series. Host Jacqueline Howard takes the viewer inside Fermilab and explains how scientists look for the smallest components that make up our world. Fermilab Deputy Director Joe Lykken talks about the new discoveries we hope to make in exploring the the subatomic realm.

View the 3-minute video at Huffington Post.

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Hidden gender bias still influences physics field

Wednesday, August 6th, 2014

This article appeared in Fermilab Today on Aug. 6, 2014.

Yale University astrophysicist Meg Urry spoke about gender bias in science at the July 30 Fermilab Colloquium. Photo: Lauren Biron

Yale University astrophysicist Meg Urry spoke about gender bias in science at the July 30 Fermilab Colloquium. Photo: Lauren Biron

Both men and women need to improve how they evaluate women in the sciences to help eliminate bias, says Meg Urry, who spoke at last week’s Fermilab Colloquium. People of either gender fall victim to unconscious prejudices that affect who succeeds, particularly in physics.

“Less than 20 percent of the Ph.D.s in physics go to women,” Urry noted, a figure that has barely crept up even while fields such as medicine have approached parity.

Urry, a professor at Yale University and president of the American Astronomical Society, unleashed a torrent of studies demonstrating bias during her talk, “Women in Physics: Why So Few? And How to Move Toward Normal.”

In one example, letters of recommendation for men were more likely to include powerful adjectives and contain specifics, while those for women were often shorter, included hints of doubt or made explicit mention of gender.

Another study found that in jobs that were perceived as masculine, both men and women tended to award the position to the man even when the woman was the qualified individual.

Other data showed that women are less likely to be perceived as the leader in mixed-gender scenarios, Urry said. When small numbers of women are present, they can become an “other” that stands in for the whole gender, magnifying perceived mistakes and potentially confirming a bias that women are less proficient in physics.

“You need a large enough group that people stop thinking of them as the woman and start thinking of them as the scientist,” Urry said.

Urry advised the many young women in the audience to own their ambition, prep their elevator speeches, get male allies who will stand up if female voices are ignored, practice confidence and network. Above all, she said, work hard, do interesting work, and don’t be discouraged if things get rough.

Meanwhile, Urry said, leaders need to learn about bias, actively look for diverse candidates rather than wait for applications, mentor and prevalidate women, such as when introducing a speaker.

Urry worked hard to debunk the myth that hiring more women means lowering the bar for diversity’s sake.

“When you hire a diverse group of scientists, you are improving your quality, not lowering your standards,” Urry said, echoing sentiments from her lunchtime talk with 40 women. “We should be aspiring to diversity of thought to enrich science.”

Lauren Biron

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Accelerator physicist invents new way to clean up oil spills

Wednesday, July 30th, 2014

This article appeared in Fermilab Today on July 30, 2014.

Fermilab physicist Arden Warner revolutionizes oil spill cleanup with magnetizable oil invention. Photo: Hanae Armitage

Fermilab physicist Arden Warner revolutionizes oil spill cleanup with magnetizable oil invention. Photo: Hanae Armitage

Four years ago, Fermilab accelerator physicist Arden Warner watched national news of the BP oil spill and found himself frustrated with the cleanup response.

“My wife asked ‘Can you separate oil from water?’ and I said ‘Maybe I could magnetize it!'” Warner recalled. “But that was just something I said. Later that night while I was falling asleep, I thought, you know what, that’s not a bad idea.”

Sleep forgone, Warner began experimenting in his garage. With shavings from his shovel, a splash of engine oil and a refrigerator magnet, Warner witnessed the preliminary success of a concept that could revolutionize the process of oil spill damage control.

Warner has received patent approval on the cleanup method.

The concept is simple: Take iron particles or magnetite dust and add them to oil. It turns out that these particles mix well with oil and form a loose colloidal suspension that floats in water. Mixed with the filings, the suspension is susceptible to magnetic forces. At a barely discernible 2 to 6 microns in size, the particles tend to clump together, and it only takes a sparse dusting for them to bond with the oil. When a magnetic field is applied to the oil and filings, they congeal into a viscous liquid known as a magnetorheological fluid. The fluid’s viscosity allows a magnetic field to pool both filings and oil to a single location, making them easy to remove. (View a 30-second video of the reaction.)

“It doesn’t take long — you add the filings, you pull them out. The entire process is even more efficient with hydrophobic filings. As soon as they hit the oil, they sink in,” said Warner, who works in the Accelerator Division. Hydrophobic filings are those that don’t like to interact with water — think of hydrophobic as water-fearing. “You could essentially have a device that disperses filings and a magnetic conveyor system behind it that picks it up. You don’t need a lot of material.”

Warner tested more than 100 oils, including sweet crude and heavy crude. As it turns out, the crude oils’ natural viscosity makes it fairly easy to magnetize and clear away. Currently, booms, floating devices that corral oil spills, are at best capable of containing the spill; oil removal is an entirely different process. But the iron filings can work in conjunction with an electromagnetic boom to allow tighter constriction and removal of the oil. Using solenoids, metal coils that carry an electrical current, the electromagnetic booms can steer the oil-filing mixture into collector tanks.

Unlike other oil cleanup methods, the magnetized oil technique is far more environmentally sound. There are no harmful chemicals introduced into the ocean — magnetite is a naturally occurring mineral. The filings are added and, briefly after, extracted. While there are some straggling iron particles, the vast majority is removed in one fell, magnetized swoop — the filings can even be dried and reused.

“This technique is more environmentally benign because it’s natural; we’re not adding soaps and chemicals to the ocean,” said Cherri Schmidt, head of Fermilab’s Office of Partnerships and Technology Transfer. “Other ‘cleanup’ techniques disperse the oil and make the droplets smaller or make the oil sink to the bottom. This doesn’t do that.”

Warner’s ideas for potential applications also include wildlife cleanup and the use of chemical sensors. Small devices that “smell” high and low concentrations of oil could be fastened to a motorized electromagnetic boom to direct it to the most oil-contaminated areas.

“I get crazy ideas all the time, but every so often one sticks,” Warner said. “This is one that I think could stick for the benefit of the environment and Fermilab.”

Hanae Armitage

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Fermilab technology available for license: Bed-ridden boredom spurs new invention

Thursday, July 24th, 2014

This article appeared in Fermilab Today on July 24, 2014.

Fermilab engineer Jim Hoff has invented an electronic circuit that can guard against radiation damage. Photo: Hanae Armitage

Fermilab engineer Jim Hoff has invented an electronic circuit that can guard against radiation damage. Photo: Hanae Armitage

Fermilab engineer Jim Hoff has received patent approval on a very tiny, very clever invention that could have an impact on aerospace, agriculture and medical imaging industries.

Hoff has engineered a widely adaptable latch — an electronic circuit capable of remembering a logical state — that suppresses a commonly destructive circuit error caused by radiation.

There are two radiation-based errors that can damage a circuit: total dose and single-event upset. In the former, the entire circuit is doused in radiation and damaged; in an SEU, a single particle of radiation delivers its energy to the chip and alters a state of memory, which takes the form of 1s and 0s. Altered states of memory equate to an unintentional shift from logical 1 or logical 0 and ultimately lead to loss of data or imaging resolution. Hoff’s design is essentially a chip immunization, preemptively guarding against SEUs.

“There are a lot of applications,” Hoff said. “Anyone who needs to store data for a length of time and keep it in that same state, uncorrupted — anyone flying in a high-altitude plane, anyone using medical imaging technology — could use this.”

Past experimental data showed that, in any given total-ionizing radiation dose, the latch reduces single-event upsets by a factor of about 40. Hoff suspects that the invention’s newer configurations will yield at least two orders of magnitude in single-event upset reduction.

The invention is fondly referred to as SEUSS, which stands for single-event upset suppression system. It’s relatively inexpensive and designed to integrate easily with a multitude of circuits — all that’s needed is a compatible transistor.

Hoff’s line of work lies in chip development, and SEUSS is currently used in some Fermilab-developed chips such as FSSR, which is used in projects at Jefferson Lab, and Phoenix, which is used in the Relativistic Heavy Ion Collider at Brookhaven National Laboratory.

The idea of SEUSS was born out of post-knee-surgery, bed-ridden boredom. On strict bed rest, Hoff’s mind naturally wandered to engineering.

“As I was lying there, leg in pain, back cramping, I started playing with designs of my most recent project at work,” he said. “At one point I stopped and thought, ‘Wow, I just made a single-event upset-tolerant SR flip-flop!'”

While this isn’t the world’s first SEUSS-tolerant latch, Hoff is the first to create a single-event upset suppression system that is also a set-reset flip-flop, meaning it can take the form of almost any latch. As a flip-flop, the adaptability of the latch is enormous and far exceeds that of its pre-existing latch brethren.

“That’s what makes this a truly special latch — its incredible versatility,” says Hoff.

From a broader vantage point, the invention is exciting for more than just Fermilab employees; it’s one of Fermilab’s first big efforts in pursuing potential licensees from industry.

Cherri Schmidt, head of Fermilab’s Office of Partnerships and Technology Transfer, with the assistance of intern Miguel Marchan, has been developing the marketing plan to reach out to companies who may be interested in licensing the technology for commercial application.

“We’re excited about this one because it could really affect a large number of industries and companies,” Schmidt said. “That, to me, is what makes this invention so interesting and exciting.”

Hanae Armitage

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Prototype CT scanner could improve targeting accuracy in proton therapy treatment

Monday, July 21st, 2014

This article appeared in Fermilab Today on July 21, 2014.

Members of the prototype proton CT scanner collaboration move the detector into the CDH Proton Center in Warrenville. Photo: Reidar Hahn

Members of the prototype proton CT scanner collaboration move the detector into the CDH Proton Center in Warrenville. Photo: Reidar Hahn

A prototype proton CT scanner developed by Fermilab and Northern Illinois University could someday reduce the amount of radiation delivered to healthy tissue in a patient undergoing cancer treatment.

The proton CT scanner would better target radiation doses to the cancerous tumors during proton therapy treatment. Physicists recently started testing with beam at the CDH Proton Center in Warrenville.

To create a custom treatment plan for each proton therapy patient, radiation oncologists currently use X-ray CT scanners to develop 3-D images of patient anatomy, including the tumor, to determine the size, shape and density of all organs and tissues in the body. To make sure all the tumor cells are irradiated to the prescribed dose, doctors often set the targeting volume to include a minimal amount of healthy tissue just outside the tumor.

Collaborators believe that the prototype proton CT, which is essentially a particle detector, will provide a more precise 3-D map of the patient anatomy. This allows doctors to more precisely target beam delivery, reducing the amount of radiation to healthy tissue during the CT process and treatment.

“The dose to the patient with this method would be lower than using X-ray CTs while getting better precision on the imaging,” said Fermilab’s Peter Wilson, PPD associate head for engineering and support.

Fermilab became involved in the project in 2011 at the request of NIU’s high-energy physics team because of the laboratory’s detector building expertise.

The project’s goal was a tall order, Wilson explained. The group wanted to build a prototype device, imaging software and computing system that could collect data from 1 billion protons in less than 10 minutes and then produce a 3-D reconstructed image of a human head, also in less than 10 minutes. To do that, they needed to create a device that could read data very quickly, since every second data from 2 million protons would be sent from the device — which detects only one proton at a time — to a computer.

NIU physicist Victor Rykalin recommended building a scintillating fiber tracker detector with silicon photomultipliers. A similar detector was used in the DZero experiment.

“The new prototype CT is a good example of the technical expertise of our staff in detector technology. Their expertise goes back 35 to 45 years and is really what makes it possible for us to do this,” Wilson said.

In the prototype CT, protons pass through two tracking stations, which track the particles’ trajectories in three dimensions. (See figure.) The protons then pass through the patient and finally through two more tracking stations before stopping in the energy detector, which is used to calculate the total energy loss through the patient. Devices called silicon photomultipliers pick up signals from the light resulting from these interactions and subsequently transmit electronic signals to a data acquisition system.

In the prototype proton CT scanner, protons enter from the left, passing through planes of fibers and the patient's head. Data from the protons' trajectories, including the energy deposited in the patient, is collected in a data acquisition system (right), which is then used to map the patient's tissue. Image courtesy of George Coutrakon, NIU

In the prototype proton CT scanner, protons enter from the left, passing through planes of fibers and the patient’s head. Data from the protons’ trajectories, including the energy deposited in the patient, is collected in a data acquisition system (right), which is then used to map the patient’s tissue. Image courtesy of George Coutrakon, NIU

Scientists use specialized software and a high-performance computer at NIU to accurately map the proton stopping powers in each cubic millimeter of the patient. From this map, visually displayed as conventional CT slices, the physician can outline the margins, dimensions and location of the tumor.

Elements of the prototype were developed at both NIU and Fermilab and then put together at Fermilab. NIU developed the software and computing systems. The teams at Fermilab worked on the design and construction of the tracker and the electronics to read the tracker and energy measurement. The scintillator plates, fibers and trackers were also prepared at Fermilab. A group of about eight NIU students, led by NIU’s Vishnu Zutshi, helped build the detector at Fermilab.

“A project like this requires collaboration across multiple areas of expertise,” said George Coutrakon, medical physicist and co-investigator for the project at NIU. “We’ve built on others’ previous work, and in that sense, the collaboration extends beyond NIU and Fermilab.”

Rhianna Wisniewski

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US reveals its next generation of dark matter experiments

Monday, July 14th, 2014

This article appeared in symmetry on July 11, 2014.

Together, the three experiments will search for a variety of types of dark matter particles. Photo: NASA

Together, the three experiments will search for a variety of types of dark matter particles. Photo: NASA

Two US federal funding agencies announced today which experiments they will support in the next generation of the search for dark matter.

The Department of Energy and National Science Foundation will back the Super Cryogenic Dark Matter Search-SNOLAB, or SuperCDMS; the LUX-Zeplin experiment, or LZ; and the next iteration of the Axion Dark Matter eXperiment, ADMX-Gen2.

“We wanted to pool limited resources to put together the most optimal unified national dark matter program we could create,” says Michael Salamon, who manages DOE’s dark matter program.

Second-generation dark matter experiments are defined as experiments that will be at least 10 times as sensitive as the current crop of dark matter detectors.

Program directors from the two federal funding agencies decided which experiments to pursue based on the advice of a panel of outside experts. Both agencies have committed to working to develop the new projects as expeditiously as possible, says Jim Whitmore, program director for particle astrophysics in the division of physics at NSF.

Physicists have seen plenty of evidence of the existence of dark matter through its strong gravitational influence, but they do not know what it looks like as individual particles. That’s why the funding agencies put together a varied particle-hunting team.

Both LZ and SuperCDMS will look for a type of dark matter particles called WIMPs, or weakly interacting massive particles. ADMX-Gen2 will search for a different kind of dark matter particles called axions.

LZ is capable of identifying WIMPs with a wide range of masses, including those much heavier than any particle the Large Hadron Collider at CERN could produce. SuperCDMS will specialize in looking for light WIMPs with masses lower than 10 GeV. (And of course both LZ and SuperCDMS are willing to stretch their boundaries a bit if called upon to double-check one another’s results.)

If a WIMP hits the LZ detector, a high-tech barrel of liquid xenon, it will produce quanta of light, called photons. If a WIMP hits the SuperCDMS detector, a collection of hockey-puck-sized integrated circuits made with silicon or germanium, it will produce quanta of sound, called phonons.

“But if you detect just one kind of signal, light or sound, you can be fooled,” says LZ spokesperson Harry Nelson of the University of California, Santa Barbara. “A number of things can fake it.”

SuperCDMS and LZ will be located underground—SuperCDMS at SNOLAB in Ontario, Canada, and LZ at the Sanford Underground Research Facility in South Dakota—to shield the detectors from some of the most common fakers: cosmic rays. But they will still need to deal with natural radiation from the decay of uranium and thorium in the rock around them: “One member of the decay chain, lead-210, has a half-life of 22 years,” says SuperCDMS spokesperson Blas Cabrera of Stanford University. “It’s a little hard to wait that one out.”

To combat this, both experiments collect a second signal, in addition to light or sound—charge. The ratio of the two signals lets them know whether the light or sound came from a dark matter particle or something else.

SuperCDMS will be especially skilled at this kind of differentiation, which is why the experiment should excel at searching for hard-to-hear low-mass particles.

LZ’s strength, on the other hand, stems from its size.

Dark matter particles are constantly flowing through the Earth, so their interaction points in a dark matter detector should be distributed evenly throughout. Quanta of radiation, however, can be stopped by much less significant barriers—alpha particles by a piece of paper, beta particles by a sandwich. Even gamma ray particles, which are harder to stop, cannot reach the center of LZ’s 7-ton detector. When a particle with the right characteristics interacts in the center of LZ, scientists will know to get excited.

The ADMX detector, on the other hand, approaches the dark matter search with a more delicate touch. The dark matter axions ADMX scientists are looking for are too light for even SuperCDMS to find.

If an axion passed through a magnetic field, it could convert into a photon. The ADMX team encourages this subtle transformation by placing their detector within a strong magnetic field, and then tries to detect the change.

“It’s a lot like an AM radio,” says ADMX-Gen2 co-spokesperson Gray Rybka of the University of Washington in Seattle.

The experiment slowly turns the dial, tuning itself to watch for one axion mass at a time. Its main background noise is heat.

“The more noise there is, the harder it is to hear and the slower you have to tune,” Rybka says.

In its current iteration, it would take around 100 years for the experiment to get through all of the possible channels. But with the addition of a super-cooling refrigerator, ADMX-Gen2 will be able to search all of its current channels, plus many more, in the span of just three years.

With SuperCDMS, LZ and ADMX-Gen2 in the works, the next several years of the dark matter search could be some of its most interesting.

Kathryn Jepsen

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