Thursday, June 11, 2015
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Thursday Yoga registration due June 18

Commercializing Innovation: office hours at IARC - today

International folk dancing today

Barn Dance - June 14

Monday yoga registration due June 15

NALWO lecture: Beauty of Barns - June 16

art/LArSoft course at Fermilab, free registration - Aug. 3-7

Walking Works week four winners

Wednesday Walkers

WalkingWorks program begins - register now

Pedometers available for WalkingWorks program

Fermilab Board Game Guild

Fermilab pool open, memberships available

Outdoor soccer

Scottish country dancing meets Tuesday evenings at Kuhn Barn

English country dancing at Kuhn Barn

H4 Training discount for Fermilab employees


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Special Announcement

Fermilab Users Meeting - today in Ramsey Auditorium

The 48th annual Fermilab Users Meeting continues today in Ramsey Auditorium. View the Users Meeting agenda.

Press Release

Fermilab named a Historic Site by American Physical Society

Fermilab Director Nigel Lockyer signs his name in the American Physical Society Historic Site Register while Laura Greene, vice president of APS, looks on. Photo: Fermilab

The American Physical Society has recognized the U.S. Department of Energy's Fermi National Accelerator Laboratory as a Historic Site for its nearly five decades of contributions to high-energy physics.

In a ceremony at the laboratory on Wednesday, Laura Greene, vice president of APS, presented Fermilab Director Nigel Lockyer with a plaque commemorating the lab's official status as a Historic Site. The plaque reads, in part: "In recognition of Fermi National Accelerator Laboratory for its pivotal contributions to high-energy physics, including the discoveries of the bottom and top quarks and the tau neutrino, key components of the Standard Model."

"We're very pleased to receive this official status from the American Physical Society," Lockyer said. "Fermilab's bright future is built on a tradition of strong and important work, and it's great to see that work recognized in this way."

American Physical Society Historic Sites are chosen by the APS Historic Sites Committee with the goal of raising public awareness of physics and enlightening scientists about important events and places in their field.

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CDF publishes first data from the 900-GeV Tevatron run

A recent CDF result exploits the advantages of the Tevatron's 900-GeV run. Photo: Reidar Hahn

Shortly before the Tevatron passed the baton of providing the highest-energy particle collisions to the Large Hadron Collider at CERN, physicists on CDF proposed to spend a few days with colliding beams at lower energy to study the energy dependence of certain reactions. The accelerator experts took up the challenge and delivered.

CDF has just published the first physics paper using this low-energy running, measuring the energy dependence of central, exclusive two-pion production. The paper appears in Physical Review D. Features of this energy dependence were unexpected and pose a challenge to theorists.

Proton and antiproton beams at the Tevatron were routinely injected at 150 GeV (150 billion electronvolts) and then accelerated to 980 GeV. With no acceleration, the beams collided with a total energy of 300 GeV. The collision rate was low — only 1/12 of that of the normal Tevatron run — but nevertheless high enough for some studies. The Tevatron also produced collisions at a total energy of 900 GeV. This energy matches the LHC energy at beam injection, before acceleration, so one can directly compare proton-proton interactions at the LHC with proton-antiproton interactions at the Tevatron.

The CDF collaboration thanks the Accelerator Division for their efforts in providing these unique lower-energy collisions, resulting in a physics publication (with more to come) with just a few days of special running.

Mike Albrow

In Brief

Early registration for DPF2015 open until June 15

Register now for DPF2015, the next meeting of the American Physical Society Division of Particles and Fields. Early registration is open until Monday, June 15.

DPF2015 takes place from Aug. 4-8 on the University of Michigan campus in Ann Arbor. Visit the meeting website for more information.

In the News

Supernova hunting with supercomputers

From iSGTW, June 10, 2015

As the yardstick against which outer space is measured, type Ia supernovae are famous for consistency, yet new observations suggest their origins may not be so uniform. Using theoretical calculations and National Energy Research Scientific Computing Center (NERSC) supercomputer simulations, astronomers have for the first time observed a flash of light signaling a supernova collision. This discovery points them to the supernova's home star system and implies there could be two distinct types of Ia supernova.

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Physics in a Nutshell

Turning up the energy

Click to view complete cyclotron illustration in Hyperphysics. The particle beam traverses the cyclotron gap starting near the center. It first moves from the bottom electrode to the top. Then the voltage reverses so that the beam can now cross over from the top electrode to the bottom. This pattern continues, and, with the help of a magnetic field, the beam travels in a gradually outward-moving path until it exits the cyclotron. Image: Hyperphysics

In my last column we began building a practical particle accelerator by stringing a series of radio-frequency cavities together to achieve beam energies extending into the billion-electronvolt range, the final energy depending on our persistence, wealth and available real estate. The lack of one or more of these attributes forces a more clever solution.

In 1932 Ernest Lawrence provided such a solution with his invention of the cyclotron. By this time the behavior of charged particles in magnetic and electric fields was well understood, and large electric fields had been used to accelerate protons and electrons. Lawrence's idea was to pass a beam of charged particles through a single accelerating gap many times instead of stringing many gaps together in a line. He used a magnetic field to bend the beam in a circular path, causing it to pass through two accelerating gaps on each orbit. As the beam increases in energy, it bends less in the magnetic field, resulting in a spiral path.

The beam, the magnetic field and the two accelerating gaps were contained in a vacuum chamber. The source of the magnetic field was a large electromagnet located outside the vacuum chamber. Inside the chamber were two separate D-shaped half cylinders that served as the electrodes for the accelerating voltage (see figure above). An oscillating voltage applied to the electrodes reversed direction with each half orbit of the beam so that the particles would be accelerated in both gaps (from the negative to the positive electrode, then from positive to negative, and so on). As the beam accelerated, it spiraled outward until, finally, it exited the chamber to be used for experiments. The first working cyclotron was only 10 inches in diameter and accelerated protons to 1 million electronvolts.

The primary limitation of a cyclotron is that large energies require large diameters, which means large, expensive vacuum chambers. In addition, as the beam particles approach the speed of light, the energy increases, but the velocity does not. Therefore, the time it takes to complete the longer orbits at high energy increases, and the synchronization with voltage is lost. Ed McMillan solved the synchronization problem by adjusting the phase of the voltage to match the orbital period through the acceleration cycle. However, both problems are resolved in a synchrotron where the magnetic field is ramped to higher values during the acceleration cycle to maintain the radius of the orbit at a constant value. This minimizes the requirements on the size of the vacuum chamber. Fermilab's 8-GeV Booster, its Main Injector and CERN's LHC are all examples of synchrotrons.

We moved very quickly from the most rudimentary linear and circular accelerators to the most sophisticated, leaving out many of the complex details. Future columns will examine some of the fascinating details of how these beautifully complex machines work. My goal is to qualify all Fermilab Today readers for the Main Control Room call-in list, which is used when one of the big synchrotrons needs to be tuned up. It's just like tuning a guitar with a very long neck.

Roger Dixon

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Photo of the Day

Tevatron tunnel

Leticia Shaddix took this photo on a Photography Club tour of the Tevatron tunnel near the D1 service building. Photo: Leticia Shaddix, PPD
In the News

Dark energy renders 97 percent of the galaxies in our observable universe permanently unreachable

From Forbes, June 8, 2015

When you look out at a star whose light arrives after traveling towards you for 100 years, you're seeing a star that's 100 light years away, due to the fact that the speed of light is finite. But when you look out at a galaxy whose light arrives after traveling towards you for a journey of 100 million years, you're not looking at a galaxy that's 100 million light years distant. Rather, you're seeing a galaxy that's significantly farther away than that! The reason for this is that on the largest scales — ones that aren't gravitationally bound together into galaxies, groups or clusters — the Universe is expanding. And the longer the journey of a photon from a distant galaxy to you, the farther away a galaxy not only is, but the more distant it will actually be from the light-travel-time.

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