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In this issue:
From Persis and Paul: ISMS Evaluation Report
The Paul Revere of Pulses
Word of the Week: Cathode
Building the LCLS: Weekly Update

SLAC Today

Friday - August 22, 2008

From Persis and Paul: ISMS Evaluation Report

(Photo - Persis Drell and Paul Golan)

The Department of Energy Integrated Safety Management Team completed their effectiveness review of SLAC operations last Friday; their final report is now available online. We encourage you to read the report or, at the very least, the executive summary. Everyone at this laboratory has been working hard to accomplish the necessary changes in culture that will result in a safer, more effective and more efficient operation. The review team not only appreciated the effort, they saw real change and significant progress toward effective ISMS at SLAC.

The most important observation from the review team is that they saw a different attitude toward on-site safety from the laboratory staff. This "can do" attitude concerns correction of safety problems. We heard this on the first day and consistently through their visit. This change in attitude toward safety is the foundation we will build on. Everyone at SLAC must have a safe work environment and feel empowered to commit to an accident-free and injury-free work place. All employees must feel free to make suggestions or raise concerns without fear of retribution or attribution. In other words, you have the right, and we have the responsibility, to ensure that you go home tonight as safe and healthy as when you came in this morning.  Read more...

The Paul Revere of Pulses

From a person’s point of view, the beam of electrons driving down the linear accelerator at close to the speed of light would appear as a single thread. "But from the point of view of precision electronics," explains Jachin Spencer, "you might see something, you might see nothing."

To a non-specialist, the word "beam" may be associated with columns of material or light. But on a microsecond time scale, the beam in an accelerator is actually a series of electron-bunches, more like machine gun fire than a shaft of sunshine.

Spencer, a summer student in the SULI program at the Stanford Linear Accelerator Center, is studying the performance of what is called the "fiducial pulse," a pulse of electromagnetic waves used to coordinate the timing of the accelerator. It’s the job of the fiducial pulse, Spencer says, to let electronics know "when they can look at the beam, when there’s something to see."

Both clock and courier, the fiducial pulse travels just ahead of the electron bunch, and alerts the monitoring devices that line the beam tunnel. Beam position and length monitors, cameras rigged to phosphorescent screens, and other sorts of diagnostics tools use the early warning to shutter their sensors in rhythm with the electron bunches, 30 times a second.

It’s no exaggeration to call the fiducial pulse the linchpin of the linac. Without the regularity of its preceding pulse, instruments monitoring the beam would fall out of synch with the bunches, and therefore out of synch with one another.  Read more in symmetry breaking.

Word of the Week:
Cathode

In some electrical devices, a cathode is an electrode through which electrons flow "out." Tube-type televisions and computer monitors are called "cathode ray tubes," or CRTs, because they use an electron beam that flows from a cathode to create an image. All of SLAC’s accelerators, including the linac and the SPEAR3 synchrotron, use a cathode to create the pulse of electrons to be accelerated. In the case of SPEAR and the main linac, the cathode produces electrons when it is heated. By contrast, the LCLS injector, which sends a pulse into the final third of the linac, has its own cathode that produces electrons when stimulated by a laser.

Building the LCLS: Weekly Update

Construction highlights from the Linac Coherent Light Source this week include:

• Installation of an auxiliary cooling tower to enable continued startup and monitoring of the chilled water system in the Central Utilities Plant during shutdown of the main linac

• Regrading of the "amphitheater" above the undulator hall, adjacent to building 3.1

• Final installation of the elevator in the Near Experimental Hall

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