Wednesday, July 30, 2008

AAC08 Day 3

Another packed day here at AAC08. I missed the first few minutes of the plenary session due to a teleconferencing, but still managed to get most of the going-on early in the morning.

The plenary session started with Gregory Nusinovich covering issues surrounding structure breakdowns. It's a great presentation which basically summed up all the relevant issues that we know and still don't know about vacuum breakdown. One interesting issue that he brought up is the issue of cyclic fatigue in an RF structure due to pulse heating of the structure walls in an RF magnetic field. Basically, while a lot of attention has been focused on the oscillating E-field that can produce field-emission current, the oscillating magnetic field in the RF pulse may in fact cause significant heating and possibly induce the formation of cracks in the material. These cracks could be the source of breakdown in these structures.

The next talk was by Stuart Mangles of Imperial College on Laser Wakefield Acceleration, focusing on the diagnostics and petawatt class experiment. He presented results from a recent experiment on ASTRA at Gemini.

Warren Mori of UCLA next presented a model of particle beam dynamics in plasma accelerator, focusing especially on beam loading. This was quite an informative talk because he presented a very clear background physics on the plasma dynamics due to an electron beam, especially in the non-linear regime.

We had an unscheduled presentation by Jay Hirshfield of Yale, but it was a fascinating on. He presented the first ever experimental results for LACARA - Laser Cyclotron Resonance Accelerator - at the Accelerator Test Facility (ATF) at Brookhaven. This is where they try to accelerate electrons only using lasers, no plasma or any other medium. The experiment was done last July 14-22, so it is really new. He showed both energy loss and gain, with an energy gain by the electrons of about 2 MeV. So this is essentially a successful (and encouraging) proof-of-principle experiment.

Needless to say, it was a rather exciting ending to the plenary session.


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