Novel techniques of laser acceleration: from structures to plasmas BY S. KALMYKOV 1 , O. POLOMAROV 1 , D. KOROBKIN 1 , J. OTWINOWSKI 1 , J. POWER 2 AND G. SHVETS 1, * 1 Department of Physics and Institute for Fusion Studies, The University of Texas at Austin, One University Station C1500, Austin, TX 78712, USA 2 High Energy Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA Compact accelerators of the future will require enormous accelerating gradients that can only be generated using high power laser beams. Two novel techniques of laser particle acceleration are discussed. The first scheme is based on a solid-state accelerating structure powered by a short pulse CO 2 laser. The planar structure consists of two SiC films, separated by a vacuum gap, grown on Si wafers. Particle acceleration takes place inside the gap by a surface electromagnetic wave excited at the vacuum/SiC interface. Laser coupling is accomplished through the properly designed Si grating. This structure can be inexpensively manufactured using standard microfabrication techniques and can support accelerating fields well in excess of 1 GeV m K1 without breakdown. The second scheme utilizes a laser beatwave to excite a high-amplitude plasma wave, which accelerates relativistic particles. The novel aspect of this technique is that it takes advantage of the nonlinear bi-stability of the relativistic plasma wave to drive it close to the wavebreaking. Keywords: advanced accelerators; SiC; surface waves; plasma beatwave accelerator 1. Introduction The ability of a laser beam to concentrate large amounts of electromagnetic energy in a small volume over a short period of time makes laser-driven acceleration techniques promising for future compact accelerators. Extremely high accelerating gradients delivered by lasers may result in a significant reduction of the accelerator size. Because the electric field of a laser is predominantly transverse, it has to be rotated using an accelerating structure in order to impart energy to a charged particle. The structure can be based either on a solid material, or on a plasma. While breakdown, single-pulse heating and the resulting cyclic stress are not important for a plasma-based structure, those issues are of the utmost importance to solid structures (Whittum 1999). Examples of the solid laser-driven structures include an open grating in an Phil. Trans. R. Soc. A (2006) 364, 725–740 doi:10.1098/rsta.2005.1734 Published online 24 January 2006 One contribution of 15 to a Discussion Meeting Issue ‘Laser-driven particle accelerators: new sources of energetic particles and radiation’. * Author for correspondence (gena@physics.utexas.edu). 725 q 2006 The Royal Society