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In this issue:
Say Cheese! Today at 11:25 a.m.
Colloquium: How Do We Know Human Activities Influence Global Climate?
SSRL Users Return

SLAC Today

Monday - November 5, 2007

Peter Ginter took this photo of SLAC's Research Yard in 2002.

Say Cheese! Today at 11:25 a.m.

Come one, come all! World-famous photographer Peter Ginter is on site this week to photograph SLAC, and as the crowning shot he would like to take a photo of the laboratory staff. The new collection of photographs focuses on the strengths of SLAC, and of course SLAC's greatest strength is its staff.

You are cordially invited to participate in the photo shoot this morning at 11:25 a.m. on the cafeteria patio. The more people the better, so please bring your entire working group with you. Come as you are—if you wear a hard hat at work, wear a hard hat in the photo. We want to show the range and diversity of activities and people at the laboratory. This should be fun and a great souvenir for all of us. 

Colloquium Monday

How Do We Know Human Activities Influence Global Climate?

Estimates of the amount of atmospheric water vapor over oceans. (Click on image for larger version and full caption.)

Human activities have significantly altered not only the chemical composition of Earth's atmosphere, but also the climate system. Human influences have led to increases in well-mixed greenhouse gases, decreases in stratospheric ozone and changes in the atmospheric burdens of sulfate and soot aerosols. Human-induced changes in the concentrations of these constituents modify the natural radiative balance of Earth's atmosphere, perturbing climate.

Quantifying the size of the human effect on climate is a difficult statistical problem. "Fingerprint" methods are typically used for this purpose. These methods involve rigorous statistical comparisons of modeled and observed climate change patterns.

In this afternoon's colloquium, Benjamin D. Santer of Lawrence Livermore National Laboratory will discuss recent fingerprint work that considers climate variables including ocean heat content, stratospheric temperatures, Northern Hemisphere sea ice extent, sea level pressure, atmospheric water vapor, and the height of the tropopause. Santer will explain how these studies illustrate that a human-induced climate change signal is identifiable in many different variables and geographic regions.

The colloquium will take place at 4:15 p.m. today in Panofsky Auditorium. All are invited to attend.

SSRL Users Return

Stanford Synchrotron Radiation Laboratory.

It's homecoming week as the users return to the Stanford Synchrotron Radiation Laboratory (SSRL) today, on schedule after the routine three-month shutdown that began August 6.

During the annual downtime, the engineers had planned to install a new insertion device for Beamline 13, but the undulator didn't arrive when expected. They worked hard to get the equipment needed to have Beamline 13 operational this year, said Tom Rabedeau, leader of the SSRL beamline development group.

With a frame borrowed from the Advanced Photon Source at Argonne National Laboratory in Illinois, and an undulator magnet array scavenged from SSRL's Beamline 5, Beamline 13 will commence commissioning sometime this fall.

The undulator switch made 2007 a tough year for all involved, said Ben Scott, supervisor of SSRL mechanical systems.

Other large projects included moving the Beamline 4 wiggler magnet and beamline to a new location, to allow for the future seismic upgrade of the shielding. As a tool to improve beam stability the hydrostatic leveling system was extended around the whole of SPEAR.

The 170-foot transport line that connects the booster to the Stanford Positron Electron Accelerating Ring (SPEAR) was also upgraded, getting rid of leaky seals in favor of an all-metal system.

"Around 70 components got rebuilt," Scott said. "A lot of that, the users won't see, although they will certainly benefit."

Many upgrades were tiny steps towards the goal of using top-off injection, which will allow the SSRL to maintain nearly constant current at 500 milliamps instead of the present 100 milliamps that has to be refilled three times a day due as it loses current.

"Like most every other summer shutdown, we just basically tore the machine apart and put it back together," Rabedeau said.

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