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In this issue:
Laser Creates Extremely Small Electron Bunches
Colloquium Monday: Pierre Auger Results
symmetry: On the Trail of Cosmic Bullets
Safety-Compliant Subcontractors List Now Online

SLAC Today

Monday - January 14, 2008

Laser Creates Extremely Small Electron Bunches

The experimental equipment that splits electron bunches into tiny microbunches to be accelerated by laser light.

Using red laser light, experimenters have successfully divided up a standard bunch of electrons into a train of extremely small bunches. This is a positive step toward their overarching goal to accelerate electrons with laser light rather than microwave power.

Laser light has the potential to imbue electrons with an order of magnitude more energy per meter than current microwave-based acceleration, possibly leading to smaller and less expensive accelerators.

In the E-163 experiment conducted last December, graduate student Chris Sears, physicist Eric Colby and the advanced accelerator research team used a red-wavelength laser to divide up 1-picosecond-long electron bunches generated by the Next Linear Collider Test Accelerator in End Station B. The resulting "microbunches" have the right spacing to be accelerated by laser light.  Read more...

Colloquium Monday

Colloquium: Correlation of the Highest Energy Cosmic Rays

The Pierre Auger Cosmic Ray Observatory, currently in the final stages of construction in Malarg├╝e, Argentina, is a ground-based observatory that observes ultra-high-energy cosmic rays. While much progress has been made in nearly a century of research in understanding cosmic rays with low to moderate energies, those with extremely high energies remain mysterious.

In this afternoon's colloquium, Fermilab's Aaron Chou will discuss recent work in which he and collaborators used data collected at the Pierre Auger Observatory to demonstrate that there is a correlation between the arrival directions of cosmic rays with energy above approximately 6 x1019 electron volts and the positions of active galactic nuclei lying within approximately 75 megaparsecs.

The correlation observed by Chou and his colleagues is compatible with the hypothesis that the highest energy particles originate from relatively nearby extragalactic sources whose fluxes have therefore not been significantly reduced by interaction with the cosmic background radiation. Active galactic nuclei or objects having a similar spatial distribution are possible sources.

The colloquium will take place at 4:15 p.m. today in Panofsky Auditorium. All are invited to attend.

Safety-Compliant Subcontractors List
Now Online

The SLAC Purchasing Department recently posted the ES&H Safety-Compliant Subcontractors List to its website.

This interactive list of potential construction subcontractors shows each subcontractor's compliance status for Injury and Illness Prevention Plan (IIPP) and the Lockout/Tagout (LOTO) Inspection Process. The list also identifies the subcontractor’s applicable Contractors State License Board (CSLB) Classifications as well as their Experience Modification Rate (a widely used indicator of a contractor’s past safety performance).

This list will aid University Technical Representatives and construction services requisitioners alike, facilitating increased communication and information flow between the Purchasing Department and the field. 

symmetry: On the Trail of Cosmic Bullets

Do the most energetic particles in the universe come from supermassive black holes? New results from the Pierre Auger Observatory make that case.

Argentina’s Pampa Amarilla is a rather remote place, a dry plain stretching thousands of miles against the spectacular backdrop of the rugged, snowcapped peaks of the Andes.

Like every other place on Earth, the yellow pampa is bathed in a constant shower of cosmic rays—protons and atomic nuclei that fly through the universe at close to the speed of light. While some are known to come from the sun, most take a meandering path that gives no clue to where they came from.

Read more in symmetry...


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