### Session R5: Advanced Acceleration Techniques

Sponsoring Units: DPB DPP
Chair: Warren Mori, University of California, Los Angeles
Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), Promenade C

 Monday, April 14, 2008 10:45AM - 11:21AM R5.00001: Plasma Acceleration Invited Speaker: Chan Joshi The energy frontier of particle physics is several trillion electron volts, but colliders capable of reaching this regime are costly and time-consuming to build; it is therefore important to explore new methods of accelerating particles to high energies. Plasma-based accelerators are particularly attractive because they are capable of producing accelerating fields that are orders of magnitude larger than those used in conventional colliders. In these accelerators, a drive beam (either laser or particle) produces a plasma wave (wakefield) that accelerates charged particles. The ultimate utility of plasma accelerators will depend on sustaining ultrahigh accelerating fields over a substantial length to achieve a significant energy gain. In this talk I will show recent results on the energy doubling of 42 GeV electrons at the Stanford Linear Accelerator Center (SLAC) in less than one meter using a plasma accelerator. Most of the beam electrons lose energy in exciting the plasma wave, but some electrons in the back of the same beam pulse are accelerated with a field of $\sim$52 GV m$^{-1}$. This effectively doubles their energy, producing the energy gain of the 3-km-long SLAC accelerator in less than a metre for a small fraction of the electrons in the injected bunch. I will discuss how this new technique may affect future colliders for high energy physics. Monday, April 14, 2008 11:21AM - 11:57AM R5.00002: High energy particle accelerators that can fit on a (large) tabletop by using lasers Invited Speaker: Wim Leemans Accelerators are essential tools of discovery and have many practical uses. At the forefront of accelerator technology are the machines that deliver beams for particle physics, for synchrotron and free electron based radiation sources. The technology that drives these accelerators is extremely sophisticated but is limited by the maximum sustainable accelerating field. This impacts the size and cost of the device. More than two decades ago, lasers were proposed as power source for driving novel accelerators based on plasmas as the accelerating medium. An overview will be presented of what these devices can produce to date, including the 2004 demonstration of high quality electron beams [1] and the 2006 demonstration of GeV class beams from a 3 cm long accelerating structure [2]. We then discuss the key challenges for broad applicability of the technology and our goal of making a laser accelerator driven a VUV/soft x-ray free electron laser. \newline [1] C.G.R. Geddes et al., Nature \textbf{431}, 538-541 (2004); S.P.D. Mangles et al., ibid 535-538; J. Faure et al., ibid. 541-544. \newline [2] W.P. Leemans et al., Nature Physics \textbf{2}, 696-699 (2006). Monday, April 14, 2008 11:57AM - 12:33PM R5.00003: High Gradient Dielectric Structure Based Wakefield Experiments at ANL Invited Speaker: Wei Gai The Argonne Wakefield Accelerator Facility (AWA) is dedicated to the study of electron beam physics and the development of accelerating structures based on electron beam driven wakefields. In order to carry out these studies, the facility employs a photocathode RF gun capable of generating electron beams with high bunch charges (up to 100 nC) and short bunch lengths. This high intensity beam is used to excite wakefields in the structures under investigation. The wakefield structures presently under development are dielectric loaded cylindrical waveguides with operating frequencies of 10 -15 GHz. Recent experiments have shown $\sim$ 100 MV/m gradient in a dielectric structure without any sign of break down with the wakefield pulse length of several nano-seconds. We present the detailed experimental results and future plan for the potential HEP accelerator applications.