Monday - October 5, 2009
SLAC Today is
available online at:
http://today.slac.stanford.edu
In this issue:
Crafting Coherence
Welcome, New SLACers!
Changes Coming—Check Your Charge Numbers
Colloquium Next Monday: What Stanford, WWII, SLAC and Silicon Valley Owe to W. W. Hansen—New Insights
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Monday - October 5, 2009 |
Crafting Coherence The Echo-7 experiment will take infrared laser light (top) and transform it into deep ultraviolet laser light with both spatial and temporal coherence (bottom). (Image courtesy the researchers.)
With experimentalists just beginning to reveal the ultrafast secrets of atoms and molecules in motion with the Linac Coherent Light Source, researchers at SLAC are already working on the next generation of X-ray free electron laser. Building on theoretical work by SLAC beam theorist Gennady Stupakov, the Echo-7 experiment will test a new way to produce an X-ray beam with an important characteristic not found in today's X-ray lightsources. "The idea behind this new scheme is to improve the quality of the beam," said Stupakov. "The beam in a self-amplified spontaneous emission free electron laser is excellent, but we would like to add an important quality: temporal coherence." The X-ray beam created by a self-amplified spontaneous emission, or SASE, free-electron laser—like the Linac Coherent Light Source at SLAC, the [upcoming] XFEL at DESY and the SPring-8 Compact SASE Source at SPring-8—has high spatial coherence, meaning that the signals at different points in space are highly correlated. But such a laser beam does not have high temporal coherence, meaning that the beam consists of many chaotic spikes instead of a well-defined, smooth shape over time. Such is the nature of these new SASE machines. In February of this year, Stupakov published a paper in which he envisioned echo-enabled harmonic generation, or EEHG, a process by which researchers could create a free electron laser with both types of coherence. To do this, an electron beam would need to interact with a "seed" laser that already has temporal and spatial coherence, albeit with a longer wavelength than the researchers ultimately need. Interaction with the seed laser would cause the electrons in the beam to pack into bunches in just the right pattern to later generate temporally and spatially coherent X-ray light. A SASE free-electron laser, in comparison, begins not with a seed laser but with random noise, which leads to its lack of temporal coherence. Read more...  (Photo by Doug Kreitz.)
Welcome, New SLACers!New SLAC staff attending the New Employee Orientation on October 1 included: Front row, from left: Paul Beardslee, Donald Lemma, Alejandro David, Emanuel Strauss Back row, from left: Allan Lazarus, Alison Chaiken, Jacki Cardoso, Michael Dunning, Luc Patthey Welcome to SLAC! Changes Coming—Check Your Charge NumbersWhile closing the books and wrapping up Fiscal Year 2009, a team from the SLAC Office of the Chief Financial Officer and the Directorates has been hard at work on a new accounting structure to reflect the matrixed nature of the lab's work. Many changes are in process: opening new charge numbers to reflect the lab's structure, setting up new service centers and closing charge numbers that should no longer be used. The new charge numbers will support the Work Breakdown Structure being implemented for 2010. Please be aware that charge numbers you use on your time sheet or for ordering goods or services may have changed effective October 1, 2009. Please check with your directorate's point of contact for guidance: PPA - Rafael Alva
Colloquium Next Monday: What Stanford, WWII, SLAC and Silicon Valley Owe to W. W. Hansen—New Insights Next Monday at 4:15 in Panofsky Auditorium, Stanford Consulting Professor of Electrical Engineering David Leeson will present new information about the life and work of klystron co-inventor and builder of the first Stanford linear electron accelerator W. W. Hansen. Leeson, in connection with his publishing of Hansen's long-lost WWII MIT Rad Lab "Notes on Microwaves," has unearthed original source materials that cast new light on Hansen's brilliant career. Leeson holds degrees from Caltech, MIT and Stanford, and has worked on applications from radar to spacecraft. In 1968 he founded California Microwave, Inc., from which he retired in 1994 to join the Stanford faculty. |
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