Monday - January 14, 2008
SLAC Today is
available online at:
http://today.slac.stanford.edu
In this issue:
Laser Creates Extremely Small Electron Bunches
Colloquium Monday: Pierre Auger Results
symmetry: On the Trail of Cosmic Bullets
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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... |
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Colloquium: Correlation of the Highest Energy Cosmic Rays
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. |
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The Pierre Auger
Cosmic Ray Observatory, currently in the final stages of construction in Malargüe, 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.
Do the most energetic particles in the universe come from supermassive black holes? New results from the Pierre Auger Observatory make that case.