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In this issue:
From the Director of LCLS: Ramping Up User Science
SLAC in Science
LSST Workshop Digs into the Details
Word of the Week: Coupling Constant

SLAC Today

Friday - October 9, 2009

From the Director of LCLS:
Ramping Up User Science

(Photo - Jo Stohr)

Last week, on October 1, SLAC Today reported the beginning of the first user run at the Linac Coherent Light Source, and on October 6, a sparkling cider toast on the roof of the Near Experimental Hall, initiated by happy users, commemorated its successful completion. By now, a second group of users has already started their LCLS experiments. These are exciting days for LCLS with recent stories in Nature and Science (subscription required), and scientists around the world waiting to see the first results. Stay tuned!

Yet LCLS development is ongoing. These early LCLS experiments are teaching us a great deal about the first-in-kind machine, and could be better termed "user assisted commissioning." LCLS as a construction project is not complete. Construction is still going on in the Far Experimental Hall and across the road from the Near Experimental Hall, where the office building for the LCLS staff is under construction. Also, of the six LCLS experimental stations, only the first one, designed for the study of free atoms and molecules, so-called AMO science, has been completed. While instruments for the other experimental stations or hutches are still being assembled, AMO users have been given early access to the LCLS X-rays. "User assisted commissioning" is led by the LCLS instrument scientists John Bozek and Christoph Bostedt, who commissioned the AMO instrument. John and Christoph still oversee the day-to-day operation on the experimental floor but as of October 1, the science topics are defined by user teams, led by a principal investigator. The experiments were selected by a peer reviewed proposal process and for the period October 1- December 21 are listed on the LCLS User Resources Web site Read more...

SLAC in Science

Science writer Adrian Cho paid SLAC a visit in recent months, and has written a thought-provoking perspective in the latest issue of Science. "For a Famous Physics Laboratory, A Quick and Painful Rebirth" (subscription required) explores the lab's transition to multi-program operations, from the final data-taking at BaBar to the launch of the Linac Coherent Light Source.

LSST Camera Workshop Digs into the Details

LSST camera with a 6 foot person for scale. (image: LSST Corporation.)

Today the Large Synoptic Survey Telescope camera team concludes a five-day workshop, which brought together an international body of about 50 scientists and engineers to discuss technical progress and ongoing development. The meetings and breakout sessions, held in SLAC's Panofsky and Kavli Auditoriums, focused on collaboration and design specifics for what will be the world's largest digital camera.

"The goals of the meeting were to discuss key issues and requirements, promote communication with partner institutions and generate a clear path forward for upcoming reviews," said Nadine Kurita, a mechanical engineer at SLAC and camera project manager for LSST.

Separate teams, representing nearly 30 institutions, are designing different components of the camera and the meeting's main challenge was figuring how to have the respective pieces work smoothly together. An important goal was making sure that the camera's lenses, filters, shutter and 65-centimeter diameter silicon detector plane will interface correctly. In a talk about development plans on Monday, Dick Horn, a former systems engineer from NASA's Goddard Space Flight Center, stressed integration across all subsystems and cautioned that the teams are "not designing in a vacuum or a stovepipe."  Read more...

(Image - chalkboard calculations)
(Image: Symmetry Magazine.)

Word of the Week: Coupling Constant

Coupling constants are dimensionless numbers used to describe the relative strengths of the four fundamental forces: the electromagnetic, strong, weak and gravitational forces. There's a lot of variation within the quartet—at low energies, the coupling for the strongest force (the strong force) is some 1 x 1039 times larger than the coupling for the weakest (gravity).

But as it turns out, coupling constants aren't really all that constant. In higher-energy processes, the strong coupling gets smaller and the electromagnetic and weak couplings get larger. According to some theories, at energies upward of 1014 GeV, the strengths of those three forces converge, creating a single unified force. Whether or not this actually happens is one of the biggest questions in particle physics.


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