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In this issue:
Triggering ATLAS
Safety Today: Dealing with Change
Word of the Week: "Current"
McCallum-Turner Considers ES&H

SLAC Today

Tuesday - September 18, 2007

The ATLAS detector.
(Image courtesy of Eric Doyle.)

Triggering ATLAS

When the Large Hadron Collider (LHC) begins scientific experiments in Geneva next year, bunches of 100 billion protons will cross paths 40 million times every second in the A Toroidal LHC ApparatuS (ATLAS) experiment. Although not every proton will collide with another, roughly 2 billion of them will. If each collision were recorded, the data would fill 6 million CDs every minute. There is no physical way that scientists could record that much information, but that's okay. They don't want to.

Not every event at ATLAS will contain "new" physics that scientists want to record, so there should be enough computer storage space to save these. But choosing which events to keep and which to ignore is a major challenge. "Triggering" software, which separates the best from the rest, has been around for decades. Not only does the software have to be fast, making decisions of whether or not to record an event in 40 microseconds, it has to be accurate. Throwing away events showing new particles being created would undermine the entire experiment. These are the challenges and pressures that SLAC physicists Sarah Demers and Ignacio Aracena face on a daily basis as they program triggers for the ATLAS experiment.

"It's a major challenge to balance the speed of the algorithms with their accuracy," said Aracena. "But it's a lot of fun." Read more...

(Column - Safety Today)

Dealing with Change

Last week, SLAC employees were notified of substantial changes within the lab's operational and science research structure. Although change is constant and normal within organizations, SLAC recognizes that people may become uncertain and stressed, especially during times of rapid change. In some cases, employees may have questions and may not know where to turn to for assistance and guidance. The Human Resources Department suggests that employees discuss any issues with their Department Head or Group Leader.

In addition, employees may come to Human Resources for counseling and/or available information regarding the changes at the lab. Lee Lyon, (x2283), Carmella Huser, (x2358) and Barry Webb (x2355) are available for conversation regarding the changes. Anyone at SLAC may contact them directly to set up an appointment.

Stanford University and SLAC also provide many areas for assistance with concerns. The Stanford Faculty and Staff Help Center is available for counseling and consultation free of charge. To make an appointment, simply give the Help Center a call at 650-723-4577 or send an e-mail to

Word of the Week:

The term "current" in particle physics relates to the number of charged particles within an accelerator's beam and is expressed in "amperes." SLAC's SPEAR synchrotron at SSRL presently operates at a current of 100 milliamperes (one-tenth of an ampere), and the current must be topped off several times a day as the beam gradually loses electrons.

McCallum-Turner Considers ES&H

This, the third article in SLAC Today's series covering the 11 McCallum-Turner focus areas, centers on Environment, Safety and Health (ES&H).

The ES&H area of review encompasses the entire function of ES&H at SLAC. Specific areas targeted for review are adequate staffing, the internal customer service model and purchased services, line-owned assets vs. matrix assets, and support to the line from the central organization. The review will also take previous audits and Corrective Action Plans (CAPs) into account.

The McCallum-Turner team will primarily analyze ES&H at SLAC through in-depth interviews and documents such as the ES&H Manual. If any employee or user would like to set-up an interview with the team, contact SLAC's point of contact Sayed Rokni or McCallum-Turner via phone or email.

"We look forward to working with McCallum-Turner and everyone at the lab," said Rokni. "We don't know what the analysis will find, but we are confident the results will enhance the ES&H Division's ability to serve the lab and the people who work here."

McCallum-Turner can by contacted with any ideas, comments or suggestions on ES&H or any of the other focus areas via e-mail at or by phone at 926-6200.

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