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In this issue:
High-energy Electrons Could Come from Pulsars—or Dark Matter
A 35th Anniversary for SLAC X-ray Science
Colloquium Next Monday: The Compact Light Source
Around SLAC: Celebrating LCLS

SLAC Today

Monday - May 4, 2009

High-energy Electrons Could Come from Pulsars—or Dark Matter

(Image - artists's conception of FGST)
An artist's conception of the Fermi Gamma-ray Space Telescope. (Image: NASA.)

Something in our galactic neighborhood seems to be producing large numbers of high-energy electrons, according to new data gathered by the Fermi Gamma-ray Space Telescope. The electrons could be coming from nearby pulsars—or they could be a longed-for signal of dark matter, the elusive, invisible material thought to make up nearly a quarter of the universe.

FGST's Large Area Telescope, a collaboration between NASA, the U.S. Department of Energy and multiple international partners, has been scanning the skies for gamma rays and particles since its launch last summer. The LAT, which was partially constructed and assembled at SLAC, measured an unexpectedly high number of electrons with energies between 100 billion and one trillion electronvolts. This result is not likely if high-energy particles—also known as cosmic rays—are coming only from distant parts of the galaxy.

"If these particles were emitted far away, they'd have lost a lot of their energy by the time they reached us," said LAT collaborator Luca Baldini of the Istituto Nazionale di Fisica Nucleare in Pisa, Italy.

When combined with other recent results, the LAT finding provides compelling evidence that something close by—probably less than 6,000 light years away—is churning out high-energy particles. The European satellite PAMELA, for example, last fall reported detecting surprisingly large quantities of high-energy positrons, the antimatter counterparts of electrons.

"Between the PAMELA results and our results, it's very hard to construct a conventional galactic cosmic-ray model" explaining this number of high-energy particles, said SLAC Professor Elliott Bloom, who works on the LAT project. "You need relatively local sources of positrons and electrons."  Read more...

LAT collaborator Luca Latronico, from the University of Pisa in Italy, will discuss the team's results in a seminar at Kavli Auditorium on Wednesday, May 6, from 12:30 to 1:30 p.m. Also on Wednesday, SLAC physicist Philip Schuster will host a seminar and discussion on the LAT findings, 3:00–4:30 p.m. in Kavli Auditorium.

A 35th Anniversary for SLAC X-ray Science

(Image - SSRP diagram)
April 1974 drawing of plans for the first Stanford Synchrotron Radiation Project beamlines. Inset drawing at upper right shows the project's placement on SPEAR.

Thirty-five years ago this month, the Stanford Synchrotron Radiation Project—the precursor to today's Stanford Synchrotron Radiation Lightsource—began operations. The SLAC archives note that SSRP was the world's first synchrotron radiation hard X-ray lightsource based on an electron storage ring. SSRP science launched with five experimental stations sharing SLAC's first X-ray beamline.

For more about the SSRP, see the SLAC Archives and History Office SSRP timeline and photo gallery.

Colloquium Next Monday:
The Compact Light Source

(Image - SLAC Colloquium banner)

Monday, May 11, SLAC physicist Ron Ruth will present "The Compact Light Source: Its Beginning, Development and Recent Experiments."

Past research at SLAC introduced a new X-ray source concept, a miniature synchrotron light source. This early research led later to the formation of a corporation, Lyncean Technologies, to develop the Compact Light Source. The prototype development of the CLS is nearing completion now. The CLS is a near-monochromatic, tunable, homelab-size, hard X-ray source with beamlines that can be used like the X-ray beamlines at the synchrotrons—but it is about 200 times smaller than a synchrotron light source. Ruth's presentation will discuss the beginnings of Lyncean and the CLS ideas, and then introduce the basic principles, design and testing of the Compact Light Source. 

The colloquium will take place at 4:15 p.m. in Panofsky Auditorium and is free and open to all. See the SLAC Colloquium Web site for more details.

Please note that in light of the American Physical Society meeting May 2–5, there will be no SLAC colloquium today.

Around SLAC: Celebrating LCLS

(Photo - LCLS first light party)

Team members from the Linac Coherent Light Source celebrated their success at creating the world's first hard X-ray laser at a "first light" party last Thursday atop the LCLS Near Experimental Hall.

(Photos by Rod Reape.)

(Photo - LCLS first light party)

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