2 papers

title:	PRELIMINARY RESULTS FROM THE UCLA/SLAC ULTRA-HIGH GRADIENT CERENKOV WAKEFIELD ACCELERATOR EXPERIMENT
format:	conference procceeding
conference:	Erice 2005
year:	2006
12 authors:	M. C. Thompson | H. BADAKOV | J. B. Rosenzweig | G. Travish | M. Hogan | R. Ischebeck | N. Kirby | P. Muggli | A. Scott | R. Siemann | D. Walz | R. Yoder
abstract:	The first phase of an experiment to study the performance of dielectric Cerenkov wakefield accelerating structures at extremely high gradients in the GV/m range has been completed. This experiment takes advantage of the unique SLAC FFTB electron beam and its demonstrated ultra-short pulse lengths and high currents (e.g., ?z = 20 ?m at Q = 3 nC). The FFTB electron beam has been successfully focused down and sent through varying lengths of fused silica capillary tubing with two different sizes: ID = 200 ?m / OD = 325 ?m and ID = 100 ?m / OD = 325 ?m. The pulse length of the electron beam was varied in the range 20 ?m < ?z < 100 ?m which produced a range of electric fields between 2 and 20 GV/m at the inner surface of the dielectric tubes. We observed a sharp increase in optical emissions from the capillaries in the middle part of this surface field range which we believe indicates the transition between sustainable field levels and breakdown. If this initial interpretation is correct, the surfaced fields that were sustained equate to on axis accelerating field of several GV/m. In future experiments we plan to collect and measure coherent Cerenkov radiation emitted from the capillary tube to gain more information about the strength of the accelerating fields.
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title:	DIELECTRIC WAKEFIELD ACCELERATOR EXPERIMENTS AT THE SABER FACILITY
format:	preprint
year:
17 authors:	G. Travish | H. Badakov | A.M. Cook | J. B. Rosenzweig | R. Tikhoplav | A. Kanareykin | M.C Thompson | M. K. Berry | I. Blumenfeld | F.J. Decker | M. J. Hogan | R. Ischebeck | R. Iverson | N. Kirby | R. Siemann | D. Walz | P. Muggli
abstract:	Electron bunches with the unparalleled combination of high charge, low emittances, and short time duration, as first produced at the SLAC Final Focus Test Beam (FFTB), are foreseen to be produced at the SABER facility. These types of bunches have enabled wakefield driven accelerating schemes of multi-GV/m in plasmas. In the context of the Dielectric Wakefield Accelerators (DWA) such beams, having rms bunch length as short as 20 um, have been used to drive 100 um and 200 um ID hollow tubes above 20 GV/m surface fields. These FFTB tests enabled the measurement of a breakdown threshold in fused silica (with full data analysis still ongoing) [1]. With the construction and commissioning of the SABER facility at SLAC, new experiments would be made possible to test further aspects of DWAs including materials, tube geometrical variations, direct measurements of the Cerenkov fields, and proof of acceleration in tubes >10 cm in length. This collaboration will investigate breakdown thresholds and accelerating fields in new materials including CVD diamond. Here we describe the experimental plans, beam parameters, simulations, and progress to date as well as future prospects for machines based of DWA structures.
keywords:	pac   2007
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