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- V. Fedosseev, F. Batsch, C. Capelli, E. Chevallay, N. Chritin, S. Döbert, T. Feniet, F. Friebel, P. Gander, E. Granados, E. Gschwendtner, J. Hansen, C. Heßler, H. Panuganti, K.A. Szczurek
CERN, Meyrin, Switzerland
- M. Hüther, M. Martyanov, J.T. Moody, P. Muggli
MPI-P, München, Germany
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In the AWAKE experiment, the electron beam is used to probe the proton-driven wakefield acceleration in a 10 m long rubidium vapor source. Electron bunches are produced using an RF-gun equipped with a Cs2Te photocathode illuminated by an ultraviolet (UV) laser pulse. To generate the UV laser beam a fraction of the infrared (IR) laser beam used for ionization of rubidium is extracted from the laser system, time-compressed to a picosecond scale and frequency tripled using nonlinear crystals. The transport line of the laser beam over the 20 m distance was built using rigid supports for mirrors and air-evacuated tube to prevent any possible beam pointing instabilities due to vibrations and air convection. Construction of the UV beam optical system enables appropriate beam shaping and control of its size and position on the cathode, as well as time delay with respect to the IR pulse, i.e. with respect to the plasma wakefield seeder. In this paper, we present the design of the UV beam line and results of its commissioning regarding IR/UV conversion, beam pointing stability, and means of beam control and monitoring.
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