SLAC Today is available online at:
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In this issue:
Zebra Fish in the Mineshaft: Understanding Mercury Toxicity
Science Today: ILC - Electron Cloud Workshops
DOE Presents SLAC with "Best in Class" Award
LCLS Ice Cream Social Photos Now Online
Reminder: Tunnel Rescue Drill Begins Today

SLAC Today

Thursday - April 19, 2007

Zebra Fish in the Mineshaft: Understanding Mercury Toxicity

This cross section through the head of a juvenile zebra fish is one of many tissue samples that may help researchers understand mercury toxicity.

Zebra fish, lentil plants, contact lenses and caterpillars—these are only a few of the subjects under scrutiny by a team from the University of Saskatchewan at the Stanford Synchrotron Radiation Laboratory (SSRL) this month. The group, led by Graham George, Canada Research Chair in X-ray Absorption Spectroscopy, and Ingrid Pickering, Canada Research Chair in Molecular Environmental Science, will employ up to three separate beam lines at SSRL to perform their experiments.

In early April, the group examined a dozen samples of juvenile zebra fish, a common animal used in heavy metal toxicology studies. The fish were exposed to methylmercury cysteine—an organic form of mercury—in water over a 24-hour period when they were 3.5 days old. "There are all kinds of mysteries about how mercury poisons living things," George says. For example, the latency period observed in humans, which can last up to 150 days after ingestion and before the onset of symptoms, is poorly understood.

The group is also performing a range of other experiments including how lentil plants absorb selenium, a mineral known to neutralize arsenic in mammals. Findings from this study may be useful in harnessing selenium-rich lentil plants for use as a natural antidote to arsenic poisoning in places such as Bangladesh, where this type of poisoning is a serious hazard and diets tend to already include lentils.

(Daily Column - Science Today)

Electron Cloud Workshops


A simulation of the electron cloud in a dipole magnet, without clearing electrodes. Click here to see the simulation with clearing electrodes. (Images courtesy of L. Wang.)

Electron cloud phenomena in accelerators have become such an important topic that there have been two recent workshops on the subject. ECLOUD 07 was held April 9th through 12th in the beautifully flowering city of Daegu, Korea. Fifty participants drawn from most of the major high energy physics laboratories gathered to exchange information on the electron cloud effect and possible methods to mitigate its impact. Earlier in March, a similar number of people attended the Electron Cloud Clearing ECL2 workshop at CERN during a Geneva downpour.

Electron cloud buildup is a problem in storage rings with positively charged particles such as protons or positrons. Electrons are initially produced by either photons or beam-gas scattering and are accelerated by the positively charged beam, rapidly producing an avalanche of electrons that can then disturb the beam. Electron clouds have been a limitation at the flavor factories—Daphne, KEKB and PEP-II—and are a major concern at the Large Hadron Collider, slated to start operation later this year.

New results reported at ECL2 included remarkable progress on simulations of clearing electrodes or slots to mitigate the electron cloud impact. At ECLOUD 07, there were excellent results from the first-ever measurements of sample materials directly installed in the accelerator beam lines in PEP-II at SLAC and in KEKB at KEK. A key parameter for the electron cloud buildup is the number of secondary electrons produced when an electron hits the beam pipe, or so-called secondary electron yield. In the PEP-II and KEKB experiments, the surface secondary electron yield is measured to be close to or lower than 1 after exposure to the beam. This is an important result which shows that the electron cloud buildup can be controlled in future machines such as the ILC damping ring.

DOE Presents SLAC with "Best in Class" Award


From left to right: Butch Byers, Jonathan Dorfan, Mary Regan, Aundra Richards, Bob Kirby, and Tom Murphy.

Yesterday morning, Acting DOE Site Office Manager Aundra Richards presented the lab with a "Best in Class" award for pollution prevention on behalf of the Office of Science. The award recognizes SLAC's dedication to environmentally friendly practices, as demonstrated by the lab's chemical management system (CMS).

Butch Byers, SLAC's CMS program manager, accepted the award on behalf of the lab. Also honored at the presentation were Mary Regan, Bob Kirby and Tom Murphy, three of 44 people to receive certificates honoring their work on the project.

Congratulations to all involved in the CMS!

LCLS Ice Cream Social Photos Now Online

(Photo - Ice cream social)
Lee Lyon, Jonathan Dorfan, John Cornuelle, John Galayda, Steve Williams, Neil Calder, and Helen O'Donnell dish ice cream at last Friday's ice cream social.

Last Friday's ice cream social was a sweet success, thanks to everyone who came to celebrate the recent Linac Coherent Light Source "First Electrons" milestone. Lines were long at times, but nearly 600 people turned out to indulge in an afternoon of music and dessert. Check out photos from the event, courtesy of SLAC Photographer Diana Rogers.

Reminder:
Tunnel Rescue Drill
Begins Today

A tunnel rescue drill is scheduled for April 19th, 20th and 21st at the south adit and the SLAC Large Detector's south utility shaft, near Building 669. If you hear sirens or see rescue efforts in progress, please don't be overly concerned but do take precautions: check the surrounding area for hazards before continuing with your work.

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