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In this issue:
Symmetry: From Atom Smashers to X-ray Movies
Science Today: Holographic Electron Systems
Kavli Prizes Announced
SLAC Begins EPICS Training

SLAC Today

Thursday - May 29, 2008

Symmetry: From Atom Smashers to X-ray Movies

(Photo - Undulator)
In this artist's conception, a pulse of electrons travels a wiggling path through an undulator, an array of magnets, in the LCLS. This causes the electrons to give off intense X-ray light—shown here as a white glow—which can be used to study structures as small as atoms and molecules. (Image courtesy of SLAC InfoMedia.)

Particle physics has done far more than deepen our understanding of the fundamental make-up of matter; it has forced researchers to invent the very tools with which to conduct their work.

First came the cyclotron, a circular accelerator for smashing subatomic particles together. The cyclotron spawned generations of ever-bigger accelerators, from one that would fit in your hand to the Large Hadron Collider, soon to open on the Swiss-French border, which spans several postal codes and requires teams of thousands to operate.

As it evolved, accelerator technology unexpectedly gave rise to a whole new field called photon science. It sprang from a major hassle confronting high-energy physicists—the fact that electrons racing around in circles give off radiation in the form of X-ray light. Researchers found a way to put this "synchrotron radiation" to work; the result was a billion-fold increase in the brightness of X-rays available for probing processes at very small scales, and a new generation of machines known as light sources. 

"Light-source science was born from the table scraps and headaches of physics research," says Claudio Pelligrini, a physicist at the University of California, Los Angeles. "This is a case of using negative or unwanted phenomena, in which nature is helping us do what we want."  Read more in Symmetry...

(Daily Column - Science Today)

Holographic Electron Systems

Gravity describes the motion of the planets and other celestial objects in addition to the evolution of the Universe itself.  Because of its weakness, however, it can often be ignored in problems where one of the other three forces is involved.     

But recent developments in string theory suggest that gravity could provide unexpected insight into dynamics involving these "stronger forces."  The reason is not because the effects of gravity are significant. Rather, it relies on an amazing equivalence between theories of gravity and the theories describing other interactionsfor example, the interactions between electrons moving in a metal.

This equivalence is known as Maldacena duality or the AdS/CFT correspondence.  It states that a non-gravitational, strongly interacting field theory may be described by a weakly interacting gravitational theory.  An example of such a field theory is Quantum Chromodynamics (QCD)—the theory that describes the strong force.  This equivalence between gravitational and non-gravitational theories is not yet proved, and it is not at all obvious; however, it has passed every check since its proposal.

The proposal begins with gravity in a curved background space called anti-de Sitter space (AdS). In the language of general relativity, this space has maximal symmetry consistent with a negative cosmological constant, and, hence, negative scalar curvature. In AdS, light can travel to spatial infinity in a finite time. Thus, the boundary at infinity must be treated as part of the space. Juan Maldacena of the Institute for Advanced Study had the idea that the gravitational theory in AdS would be completely equivalent to a field theory living on the boundary. This idea makes a weird connection between a gravity theory, say, in five dimensions to a field theory like QCD in four dimensions. But it is not completely crazy. The entropy of a gravitational theory in (d+1) dimensions and the that of an ordinary field theory in d dimensions scale in the same way with the size of the system.

Kavli Prizes Announced

Seven pioneering scientists who have transformed human knowledge in the fields of nanoscience, neuroscience and astrophysics have become the first recipients of the million-dollar Kavli prizes.

The laureates were selected for their groundbreaking research that has significantly advanced our understanding of the unusual properties of matter on an ultra-small scale, the basic circuitry of the human brain and the nature of quasars.  Read more...


SLAC Begins
EPICS Training

Members of the Power Conversions Department learn about EPICS.
(Click on image for larger version.)

The Power Conversions Department had one of its first training sessions on the Experimental Physics and Industrial Controls System (EPICS) on April 29 and May 1. SLAC is in the beginning stages of a switch over to the new system, which will take a few years to complete.

The session and lab were introduced participants to building an EPICS application to "talk" to a Personal Controls Unit (PCU). PCUs can be attached to, for example, a power supply or modulator, and send the user an update of that system. The classes were taught by Steve Lewis and Stephen Schuh, with help from the EPICS team and the SLAC Controls Group.

EPICS is a collection of Open Source software tools that was pioneered by Los Alamos and Argonne National Labs and is currently used by a number of other physics laboratories including Lawrence Livermore National Lab and and Deutsches Elektronen Synchrotron (DESY).


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