From Echo-7 to Echo-15:
Upgrade Nears Completion
The new spectrometer, already installed and in use. (Photo courtesy Carsten Hast.)
by Lori Ann White
Members of the Echo-7 team are putting the finishing touches on a number of upgrades to the Next Linear Collider Test Accelerator in SLAC's End Station B. The upgrades will enable the team to delve more deeply into the physics behind last summer's successful demonstration of a phenomenon called
echo-enabled harmonic generation. A second goal is to create radiation of even greater coherence, based on higher harmonics, or related wavelengths, than were reached during those initial trials.
Originally proposed by SLAC accelerator theorist
Gennady Stupakov, EEHG shows promise as a method for generating X-ray laser pulses of even higher quality than those of the Linac Coherent Light Source. The LCSL pulses are spatially coherent but not temporally coherent—think of them as identical siblings running a race, all randomly scattered at different points along the straightaway. EEHG puts the runners at precise intervals. When translated back to X-ray lasers, the temporal coherence provided by EEHG is an important property for beams used in ultrahigh-precision microscopy and imaging studies.
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This simulation shows one of the first protostars forming, 200 million years after the Big Bang. (Reprinted with permission
from the April 2011 Physics Today. Copyright 2011, American Institute of Physics.)
Reconstructing the Earliest Stars
by Lori Ann White
A stunning glimpse of a coalescing protostar graces the April 2011 cover of
Physics Today, courtesy of Tom Abel of the joint SLAC-Stanford Kavli Institute for Particle Astrophysics and Cosmology
and colleagues from many institutions. The issue features an article by Abel, on how cosmologists use computer simulations to gain insight into astronomical objects that lie beyond the reach of the most powerful telescopes.
The article, entitled "The First Stars, as Seen by Supercomputers,"
(subscription required) describes how the simulations track the complicated interplay between gravity and gases in the early universe before the first stars formed. It is accompanied by images from several simulations. According to Abel, creating computer programs that simulate what happened in the early universe is only half the battle. Then researchers must be able to see and understand what they've got.
"It takes a very large effort to write the software to visualize the complicated data we are working with," Abel said.
KIPAC's Ralf Kaehler "does an amazing job with that. Even with software in hand, though, many creative decisions have to be made: Which data to show? The density, the temperature, the chemical composition? How to map it to color? What would a particular telescope see? We balance many possibilities for how to best convey the information to the audience."
Simulation by Matthew Turk, University of California at San Diego; Brian O'Shea, Los Alamos National Laboratory; and Tom Abel.
Image by Ralf Kaehler and Tom Abel, Kavli Institute for Particle Astrophysics and Cosmology.
(Photo by Maria Mastrokyriakos.)
Welcome, New SLACers!
by Maria Mastrokyriakos
SLAC welcomed 16 recently hired employees who attended the New Employee Orientation on April 7, 2011. Please welcome our new staff as they embark on their new career paths here at SLAC.
First Row, from the left: Leo Gonzales, Marc Welch, Michael Minitti, Susan Overholser, Zenaida Martinez, Emily So, Lisa Hammon, Astrid Tomada.
Back Row, from the left: Thomas Large, Leslie Battersby, Glenn Markle,
John Dodd, Maria Buenrostro, Chris Bloyer, Steven Arambula.
Not pictured: Elisa Hamilton.
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