CERN reports on LHC repair progress; restart still set for Fall

June 19, 2009 | 12:39 pm

CERN confirmed today that the Large Hadron Collider remains on schedule to restart this fall, albeit two to three weeks later than originally expected.  A specific restart date, and the beam energy for the initial run of the LHC, are yet to be determined.

After a much-hyped startup on September 10, 2008, the LHC shut down nine days later when a connection, or splice, between two superconducting magnets failed. Today’s press release discusses the cause of the failure and steps that have been taken over the past nine months to repair the damage to the LHC and ensure that a similar incident won’t happen again. The release also details ongoing tests to the 10,000 splices that connect the LHC magnets. The results of these tests will determine the LHC’s restart date and maximum beam energy for its first run.

For those who would like more details on the fixes to the LHC and the systems that are being put in place to prevent future incidents, the reports and past presentations of two external committees set up by CERN in the wake of the failure are available online.

The first committee was tasked with reviewing the LHC’s enhanced protection system, which will detect (and protect against) abnormally high resistance splices such as the one that caused the LHC to fail. The second panel, the LHC Risk Review, examined the risks to future operation of the LHC, taking into account the technical and operational measures planned and being implemented following the failure.

Katie Yurkewicz

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The science of talking so people want to listen

June 19, 2009 | 8:45 am

If you study high-energy particle physics, the importance and excitement of neutrinos is obvious. But how do you convey that to an auditorium of students, a member of Congress, or your neighbor?

Michael Turner

If you’re Michael Turner, a University of Chicago astrophysicist, you borrow a plot line from the classic Christmas movie, It’s a Wonderful Life. “What if neutrinos had never existed?” Turner asked in a recent public outreach lecture. Then he showed the audience a world without the subatomic particles, just as the movie showed life minus the main character George Bailey.

“No neutrinos,” Turner said. “That means no atoms, no Earth, and no us.”

Connecting science to everyday experiences in jargon free terms is key to science outreach, something Turner excels at doing. He shared his insights and tips from more than a decade worth of talks with scientists at Fermilab’s annual Users’ Meeting this month. The meeting featured a special Outreach Workshop with talks to help scientists adjust to a changing climate that requires every scientist be able to explain the value of research in language a banker with no science background would understand.

In the past, science funding was virtually assured, but today HEP physicists must vie for government support with a plethora of other scientific fields amidst an economic downturn and mounting deficit.

“There is no such thing as entitlement to science funding in this society,” said Herman White, a Fermilab scientist, who often meets with Washington policy makers. “You have to make an argument, and it has to be a good argument.”

The keys to generating interest in particle physics are: telling the story of the wonder and the cutting-edge nature of the research; building a broader base of support outside of the academic community; and explaining how basic-research funding has paid off for society with advances in technology, an educated workforce, and industrial applications.

“What we do is intrinsically interesting and important,” Turner said. “You have to work hard to make it boring.”

A recent nationwide series of lectures on the science behind the movie Angels & Demons showed that people hunger for science knowledge. More than 4600 people so far have attended 61 lectures across the United States as well as many more at lectures overseas.

Manfred Paulini, a physicist from Carnegie Mellon University who conducts research at Fermilab, had a full house for his lecture even though it was competing against the Pittsburg Penguins’ playoff hockey game and a lecture by a visiting computer scientist.  A YouTube video of his talk has garnered 16,000 hits, the second highest number of hits for a Carnegie Mellon video behind Randy Pausch’s  “The Last Lecture”.

Paulini told attendees of the Users’ Meeting what he learned about the preferences of general public audiences.

“If you think what you’re saying is too simple or too dumbed down, it is probably still too complicated,” he said.  ”Describe a scientific concept by relating it to an everyday idea,” he suggested. “Then you can reference it later in your talk, and your audience will understand what you mean.”

Don Lincoln, a Fermilab scientist, added his reflections on writing two popular science books about particle physics. “Don’t try to do a big overview,” of a broad scientific subject, he said. “Focus on a single topic. People relate to that.”

To get a good list of dos and don’ts for outreach, watch a video of Turner’s talk. He outlined the essentials of knowing your audience, using PowerPoint judiciously, using humor, exuding enthusiasm, and considering panel discussions and on-stage conversations as alternatives to the standard lecture format. Above all, keep it simple.

“We don’t have to give lectures,” Turner said. “We don’t have to use jargon. We can leave some things out. Leave them wanting more.”

Watch videos of the three Outreach Workshop panels here.

by Rachel Carr

Symmetry Intern

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Eagle eyes: Neutrinos in the movies

June 18, 2009 | 12:28 pm

Our valued reader Clark Cully, a recent alumnus of the Michican CDF group, seems to keep his physics radar on high alert even when most of us are zoning out in a dark theater, letting Hollywood think for us. Last September he noticed that a fictional time machine in the film Deja Vu bore a more-than-coincidental resemblance to the CDF detector at Fermilab. Symmetry took the tip and covered the story.

This year, Clark spotted another instance where Hollywood used real science to create science fiction. In the movie Eagle Eye, a cutting edge supercomputer looks more than a little like the Super-Kamiokande neutrino detector in Japan.

Clark isn’t the first to spot the connection–you can find mention of it here (but be warned of plot spoilers!). You can read more about the Super-K and the hard work it takes to maintain it in this symmetry breaking post.

Calla Cofield

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New ways to power particle accelerators

June 16, 2009 | 10:00 am

(From left) Test Facilities group members Keith Jobe, Zenon Szalata and Carsten Hast and Arnold Vlieks of the Klystron Department put the interlock system through its paces. (Photo by Lauren Schenkman.)

Yesterday, a team of physicists and engineers from SLAC National Accelerator Laboratory completed the final touches on a revolutionary new power source, the Marx modulator, and threw the switch. This successful milestone launches a yearlong test, the final step in proving the reliability of a device poised to transform the way particle accelerators are powered.

“It’s been a challenging developmental program, and I’m very happy to see its successful completion,” said Craig Burkhart, head of the Power Systems Development group, which began building the Marx in 2006. The device was moved last December to its current location in SLAC’s End Station B, where yesterday a team from SLAC’s Test Facilities, LC Research and Power Conversion departments ended the initial testing period with success running at klystron powers above 10MW.

Each of the SLAC linac’s 240 klystrons gets its juice from a modulator, which converts out-of-the-wall AC power into specially-shaped pulses of electrical power. The current design for the proposed International Linear Collider-the next big particle physics machine to follow the Large Hadron Collider-includes 576 klystrons, each with its own modulator. But today’s modulators are bulky and awkward. Each one requires a transformer about about the size of a Mini Cooper. To prevent sparks, these transformers must be submerged in an insulating bath of hundreds of gallons of mineral oil. And because transformer size grows with the pulse length, the ILC’s long pulses would require about 22 feet of tunnel length per modulator.

Technician Alfred Viceral opens the Marx modulator's cage to perform fine tuning during downtime. (Photo by Lauren Schenkman.)

The sleek device plugged in yesterday could make these dinosaurs history. The Marx takes up less than 10 feet of tunnel space and weighs a fraction of what a traditional modulator does. Its design is simple and elegant-eight pairs of flat vertical cells, or cards, fit onto a central support like ribs on a backbone. Each is equipped with eight cylindrical capacitors, each about half the size of a paper towel roll, configured to act like a single capacitor.

The key to the Marx lie in its solid state switches, which can quickly reconfigure the interconnection between cards. The cards charge in parallel, but discharge in series, so they dump their power into the klystron in one pulse of 120,000 volts. Impressively, because of the rounded edges of each aluminum rib, these 120,000 volts can sit safely in air without producing a spark. No mineral oil is required, just a simple metal cage. Additionally, the Marx transforms 96 percent of the AC power coming in to pulsed power going out, improving current modulator efficiency by one third.

Connecting a klystron to a power source like the Marx isn’t as simple as plugging in a power cord. The Test Facility team, led by physicist Carsten Hast, needed a way to protect the klystron from possible failures. Under the leadership of Ray Larsen and Bill Ross (now retired) the Controls Group built an electronic safety interlock system called the Fast Fault Finder. The Fault Finder diagnoses sparks if the klystron or Marx malfunctions, within a micro-second or two. In addition, it talks to sensors that monitor klystron vitals such as pressure and temperature. If these slip outside a given range, the Fault Finder cuts the power to the Marx, protecting the klystron.

The Marx modulator. (Photo by Lauren Schenkman.)

The Marx may be leaner, meaner and even greener than its predecessors, but old-fashioned modulators have been a reliable mainstay of accelerators for decades. Only a successful extended test, like the year-long trial commenced yesterday, can convince accelerator physicists to leave current modulators for this novel, space-saving, energy-efficient approach.

“Modulators haven’t changed much since the 1940s, so gaining acceptance of a new technology is a very significant and challenging feat,” Burkhart said. “It has to prove itself on a lot of fronts to gain acceptance in the accelerator community.”

“Each subcomponent [of the ILC] has to be reliable,” said Chris Adolphsen, who coordinates SLAC’s research and development efforts for powering the ILC. “We want to show that [the Marx] works for hundreds, thousands of hours. We’ll run for a year and see what fails, and what doesn’t fail, and learn from that.”

The Power Conversion Department is working on a second-generation Marx with redundant features-one pair of the device’s cards would be spare, taking over automatically if a running pairs fails. The upgrade would mean that the ILC could sail through faults and problems without losing valuable uptime.

“You could fix cards that are bad, and you don’t immediately have to shut it off,” Adolphsen said.

Burkhart added that continued testing of the Marx can help researchers find ways to utilize it in contexts other than the ILC. “Right now we’re doing this development for a very specific application,” he said, “but I believe that as the technology matures we’ll find applicability to a much broader range of applications.”

By Lauren Schenkman

This story first appeared in SLAC Today on June 16, 2009.

Symmetry Intern

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Rare isotope rap

June 15, 2009 | 10:25 am

Steve Koonin, Under Secretary for Science at the US Department of Energy, was among those at Michigan State University on Friday for an event to celebrate the future of rare isotope research in the United States. (Here’s an interview Koonin did on the subject.) For the most part Koonin was treated to what amounts to usual fare at these types of events-tours of the facility (in this case National Superconducting Cyclotron Laboratory); interviews with local media; and an audience with local, state, and federal officials, including both of Michigan’s senators, Carl Levin and Debbie Stabenow. However, one part of the program defied the norm.

Kate McAlpine, whose Large Hadron Rap has been seen 5 million times (and counting) on YouTube, premiered a new rap video, this one about (you guessed it), rare isotopes. And while it looks great on YouTube, particularly the HD version, the experience of seeing it on three elevated screens 14′ across while the beat thumped through a high-end sound system was memorable, especially since one senior faculty member figures prominently in the video. That would be Brad Sherrill, MSU University Distinguished Professor and designated chief scientist of the Facility for Rare Isotope Beams, FRIB, which will be established at MSU over the next decade. (Here’s Sherrill doing more conventional science communication about rare isotope research.)

Despite all the senior scientists and politicians on hand that day, McAlpine herself was the subject of several interviews. One local TV reporter even asked her is she thought a recording contract might be in her future.

McAlpine’s answer: “I don’t think that’s going to happen anytime soon.”

But with a few more of these, who’s to say it won’t?

Read more about rare isotope research in the symmetry feature “Probing the heart of the atom“.

Geoff Koch

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High-energy dragon boating

June 12, 2009 | 10:20 am

Members of the DrArgonnes at practice Wednesday night on the Fox River.

A long, thin boat with a mythical head slips through the water propelled by oars slapping the water in time with the beat of a tribal drum. As the rowers heave backwards, the 1900 lb. craft slithers forward. From the shore comes the chant “E=mc²“.

This group doesn’t need help to know that they can turn their muscle mass into speed. Several of the scientists in the boat powered their way up the leader board at last year’s dragon boat race as members of the Draggin’ Runners.

With a new team of six scientists from Fermilab and 14 from Argonne National Laboratory, plus a new name, DrArgonnes, they practiced for a title shot at this weekend’s St. Charles Pride of the Fox RiverFest in Illinois.

“It’s exhausting while you’re doing it but exhilarating when you cross the finish line,” said the Fermilab CDF experiment’s Jennifer Pursley.

Pursley joined the team five years ago after seeing oars in the main control room at CDF as a graduate student. Fermilab usually fields at least one team each year, giving scientists a chance to build camaraderie outside the laboratory and connect with their neighbors.

“I love the team camaraderie, it’s fun to be out on the water,” Pursley said.

This year Argonne staff joined the 20-person DrArgonnes team, which will race at 9:30 a.m. on Sunday, June 14, at Pottawatomie Park in St. Charles.

“We did this because it was fun,” said CDF’s Rick Tesarek, who has organized the team for years. “We keep doing it because it is an event we really enjoy.”

by Tia Jones

This story first appeared in Fermilab Today on June 12, 2009.

Symmetry Intern

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Using a particle accelerator to store computer data?

June 11, 2009 | 3:27 pm

Although this story is not about the science of particle physics as such, it shows one of surprising ways in which particle accelerators can be used in the development of new science and technology – Ed.

A. Theoretical prediction of the changing magnetization of a metal film when influenced only by a magnetic field. B. Theoretical prediction when influenced by both a magnetic and an electric field. C. Actual data showing influence from a magnetic and electric field. The figure-eight pattern is a magnetic contrast image. After the electron beam passes through the magnetic film, the researchers take it out of the accelerator and look at it with a SEMPA microscope—a Scanning Electron Microscope with Polarization Analysis. This microscope can "see" the magnetic orientation of electrons in the film: either to the left (white), or to the right (black). (Image courtesy of the research team.)

Five SLAC National Accelerator Laboratory scientists and their collaborators have started a new chapter in the field of electromagnetism with research that could change the way your computer stores data. Their results, which appear on the front cover of the May 29 issue of Physical Review Letters, demonstrate for the first time a way to change a magnet’s polarity using an electric rather than magnetic field.

Most computer hard drives store data using magnetic fields generated by small coils. The current flowing through the coil generates a magnetic field that flips the orientation of a series of magnets back and forth. These coils are generally bulky and the current produces a lot of heat, so scientists have theorized that your computer could apply an electric field to write data instead.

“You would have the potential for a mechanism which can switch magnets a lot faster and with a lot less heat loss,” explained Sara Gamble, a Stanford graduate student and co-author on the paper. But scientists have been unable to make an electric field affect a magnet’s polarity the way a magnetic field does. Now, Gamble and her fellow researchers have changed that, and opened the door for a new technology.

Gamble, along with fellow graduate student Mark Burkhardt, SLAC scientists H. C. Siegmann and Jo Stohr, and outside collaborators Alexander Kashuba, Rolf Allenspach, and Stuart Parkin, all specialize in magnetism. The group had set out to use the SLAC linear accelerator’s Final Focus Test Beam to study the effects generated by electron pulses of different lengths on magnetic films of metal. In the FFTB, the team worked with electron beam pulses, in which the electrons are grouped into bunches. Each bunch generates magnetic and electric fields as it passes through the metal. The magnetic field changes as it moves outward from the beam, affecting different portions of the metal film differently. As a result, the magnetization of the metal oscillates back and forth in figure-eight-like rings around the beam. But as the team applied the shorter and faster of the two beams, the resulting rings appeared warped. Something other than the beam’s magnetic field was affecting the metal’s magnetization.

As it turns out, the ultrafast electron bunches from the SLAC linac provided unique circumstances that set the stage for the team’s discovery. First, the electric fields of the shorter electron bunches are strong enough to rival the bonds that hold the metal’s atoms together. The pulses are short enough, however, to avoid breaking the atoms apart. Secondly, the electric field created by the electron bunches is spherical at rest, but when flying down the linear accelerator at nearly the speed of light, it flattens out like a pancake. Normally, the laws of physics will cause a conductor, like a sheet of metal, to block an electric field from entering into it . But the pancake-like shape of the electric field, which lies parallel to the magnetic film, allows it to penetrate into the metal. The warped circles that the team saw were the result of the electric field flipping the magnetization direction of the metal, just the way the magnetic field could. In technical terms, the team had observed the first electric-field induced magnetic switching, and had shown that this could be done more than 1000-times faster than present-day data storage.

To produce this effect with electrons requires a beam like the one at the SLAC linear accelerator, but the researchers said it would be possible to create a tabletop version using laser light. “You can get fields this strong with laser pulses, so there’s a possibility of being able to use the field of a photon pulse to do this,” Gamble said. “One day there could potentially be a table-top version of our experiment. We haven’t done that, but you can see from the physics that it is feasible.”

This story first appeared in SLAC Today on June 11, 2009.

Calla Cofield

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Happy birthday, Fermi Gamma-ray Space Telescope

June 11, 2009 | 12:56 pm

The Fermi Gamma-ray Space Telescope launched one year ago. (Photo: NASA)

Today marks one year since the Fermi Gamma-ray Space Telescope was launched into orbit. Since then, the telescope has discovered a whole new set of pulsars, gained a new view of cosmic jets, seen the most extreme gamma-ray blasts ever, created new sky maps in gamma-rays, shown that blazars are more complex than previously thought, observed a mysterious excess of high-energy electrons from space that could be from pulsars or possibly a sign of dark matter, and spotted gamma-ray bursts that lasted for half an hour rather than the expected few minutes.

Happy birthday, Fermi Gamma-ray Space Telescope!

David Harris

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Singing songs of dark energy

June 9, 2009 | 6:31 pm

University of California, Davis, professor of physics Lloyd Knox sings a song of dark energy to a student class. Listen and learn, people!

Update: Thanks to Blake Stacey of Science After Sunclipse, here is another ultra-geek video (below), this time about special relativity. Check out his post for more info and complete lyrics. Add other suggestions of geek physics videos in the comments.

David Harris

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Cracking the crusts of neutron stars

June 9, 2009 | 1:54 pm

By analyzing collisions between several combinations of tin nuclei, researchers at the Michigan State University National Superconducting Cyclotron Laboratory, or NSCL, have refined understanding of what is known as “symmetry energy.” Their work marks the first successful theoretical explanation of symmetry energy-related quantities in heavy-ion experiments. The result should help in discerning the properties of neutron stars, particularly in the crust region.

On the average, the nuclear attraction between a neutron and a proton is stronger than that between two protons or two neutrons. The nuclear contribution to the difference between the binding energy of a system of all neutrons and another with equal numbers of protons and neutrons is known as the symmetry energy. Nuclear mass formulae include a symmetry energy term. This term often takes a form that assumes the symmetry energy to be independent of density, even though its value inside the nucleus, at normal density, should exceed its value at the surface, where the density is lower and the ratio of proton to neutron densities differs from that for the nuclear interior.

The symmetry energy of a stable nucleus at typical nuclear densities contributes modestly to the binding energy and influences significantly the stability of nuclei against beta decay. Despite the sensitivity of nuclear masses to its average value, the precise understanding of its dependence on density has proved elusive, leading to large uncertainties in the theoretical predictions for properties of very neutron-rich nuclei, such as their masses or neutron skin thicknesses. The effects of the symmetry energy loom even larger in environments with unusual ratios of protons to neutrons and much larger ranges of density, such as in neutron stars. There, the dependence of the symmetry energy upon density is one of the most uncertain parts of the mathematical palette describing forces at play in such stars. Absent access to this palette, physicists’ equations can only paint the broadest outlines of these enigmatic stellar environments.

Now, Betty Tsang, Bill Lynch, Pawel Danielewicz, and colleagues have helped to constrain understanding of density dependency of symmetry energy by studying how it affects heavy-ion reactions studied at NSCL’s Coupled Cyclotron Facility. In two experiments, the researchers collided various beams of tin nuclei with a stationary tin targets. The four combinations included a tin-124 beam on a tin-124 target, tin-112 on tin-112, tin-124 on tin-112, and tin-112 on tin-124. Use of heavy ions with different neutron to proton ratios-the NSCL facility can accelerate protons up to uranium isotopes-allowed the research team to create and study nuclear matter with different neutron to proton ratios at a range of densities that can be varied by adjusting the energy of the beam and the centrality of the collisions.

NSCL professor Bill Lynch inspects the miniball, a detector at the MSU laboratory used to analyze fragments produced when nuclei collide at high velocities.

Data on several observable quantities were collected. One observable, termed isospin diffusion, probed the neutron over proton ratio of neutron-rich projectile nuclei after collisions with neutron-deficient target nuclei. During grazing collisions at relative velocities of one-third the speed of light, a neck region with reduced density can formed between projectile and target nuclei through which these nucleons diffuse. The stronger the symmetry energy is in this neck region, the more likely the neutron to proton ratios in the projectile and target nuclei will seek equilibrium and become equal. A second observable involved comparisons of neutron and proton energy spectra in central head-on collisions. In this case the symmetry energy expelled neutrons from the central overlap region of the projectile and target nuclei; the ratio of neutron over proton emission provides a probe of the variation in the symmetry energy as the system compresses and expands during the collision.

By comparing the experimental data to results obtained with theoretical models, the researchers obtained an allowed region of symmetry energy and density from normal down to a third of the nuclear matter density.  The result will help to describe the inner crust of neutron stars. The role of the symmetry energy at the cores of such stars, where the density of nuclear matter reaches 10 times normal density, is associated with the largest uncertainty. As high density regions are formed albeit fleetingly in head-on heavy ion collisions, the results suggest that symmetry energy can be studied in at higher energy in new and planned accelerator facilities in Japan (RIKEN), Germany (FAIR), and the United States (FRIB).

Geoff Koch

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