SLAC Today is available online at:
In this issue:
From the KIPAC Director: GLAST—Watcher of the Skies
Building the LCLS: Weekly Update
Word of the Week: Pump-Probe
Remembering Hobey DeStaebler

SLAC Today

Friday - June 27, 2008

From the KIPAC Director: GLASTWatcher of the Skies

(Photo - Roger Blandford)

Roughly 6,000 years ago, a 954-year-old neutron star about 10 miles in diameter spinning on its axis 30 times per second used its strong magnetic fields—in a sort of souped up LINAC—to create a gamma-ray photon. This photon escaped from a dense crowd of X-rays, electrons and positrons, all eager to make its acquaintance, into the vast reaches of interstellar space. It is now just outside of our solar system, hurtling towards Earth at the speed of light and sometime next week it will keep an appointment with a three-ton orbiting satellite: the Gamma-ray Large Area Space Telescope (GLAST).

However, just as the gamma ray meets its demise inside the GLAST detector, it will give birth to an electron and a positron, which will continue along similar trajectories before spawning several generations of descendents whose genealogy will be reconstructed using a criss-cross pattern of nearly a million Silicon strips and who will hold a family reunion in a block of Cesium Iodide at the end of the detector where each particle will create a flash of light dependent upon the energy of the original gamma ray photon. All of this information about the arrival and fate of this gamma ray will be converted into a brief radio message, which will be transmitted to Earth via another satellite, before being logged in SLAC's Large Area Telescope (LAT) Instrument Science Operations Center (ISOC), located in Building 84.  Read more...

Hobey DeStaebler

Herbert "Hobey" DeStaebler, one of the early members of SLAC, passed away on June 13, 2008 at the age of 79. He worked with Pief Panofsky, Burton Richter, Dick Taylor and many others on the very beginnings of the laboratory, and retired from SLAC in 2003.

DeStaebler first came to Stanford in 1956 after completing his thesis work at MIT on strange particle production by cosmic rays. He joined the High Energy Physics Laboratory (HEPL), pursuing experiments using the electron beams at that laboratory. Shortly after his arrival, he became one of a small number of physicists who produced a preliminary design study for a new accelerator 50 times as long as the HEPL linac: the Stanford Linear Accelerator. From that point on, he devoted his professional life to SLAC. His calculations of the radiation that could be generated by such an accelerator and of the shielding required to make accelerator operations completely safe determined the configuration of the accelerator.

"Hobey and I arrived at HEPL at the same time," said Burton Richter. "I got to know him when we worked together on an experiment as post-docs and found him to be a terrific partner. All of us at the lab came to know that if Destaebler said it was so, it was so."  Read more...

Word of the Week:

Pump-Probe is a scientific technique in which one laser beam (or magnetic pulse, etc.) is used to excite (or "pump") a sample, and a second laser beam is used to measure (or "probe") the reaction caused by the first. Researchers can use this method to study processes in materials that occur on very short timescales—on the order of quadrillionths of a second in some cases—such as how shock waves propagate across molecules. The Linac Coherent Light Source will have an experimental station dedicated to a range of pump-probe experiments.


Building the LCLS: Weekly Update

Construction highlights for the Linac Coherent Light Source (LCLS) this week include:

• Piping installation and finished floor concrete pour in the Far Experimental Hall

• Preparations for finishing out the entrance to the Access Tunnel

• Continued energization of systems in the Central Utilities Plant


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