A Solid State Accelerator

We present a solid state accelerator concept utilizing particle acceleration along crystal channels by longitudinal electron plasma waves in a metal. Acceleration gradients of order 100 GV/cm are theoretically possible, but channeling radiation limits the maximum attainable energy to lo5 TeV for protons. Beam dechanneling due to multiple scattering is substantially reduced by the high acceleration gradient. Plasma wave dissipation and generation in metals are also discussed. Presently existing high energy particle accelerators are limited to acceleration gradients of order 10 MV/meter. This implies that to achieve ultrahigh energies exceeding several TeV would require great distances. In recent years there has been an increased interest in the high-gradient linear acceleration of charged particles. ‘q2 One concept which promises very high gradients is the plasma accelerator. 3 In this scheme longitudinal plasma oscillations with phase velocities near the speed of light provide large electric fields which are intended to accelerate particles to high energy over a short distance. Gradients of order fi V/cm are theoretically possible where n is the electron number density in units of cm -3. Typical laboratory plasma densities are in the range 1014-1018 cmm3 corresponding to maximum gradients of 10 MV/cm-1 GV/cm. However a high gradient is not the only requirement for linear colliders, stability and emittance requirements for the accelerating system are very stringent. Since the beams from two independent accelerators must collide at an interaction point, excessive transverse motion and emittance growth of the beams induced during acceleration must be avoided. One concern is that plasma accelerators may be prone to such beam instabilities due to plasma non-uniformities and multiple scattering. To extend the plasma wave acceleration idea to very high gradients and avoid beam emittance degradation, we explore in this paper a solid state accelerator concept in which particles are accelerated along atomic crystal channels by plasma waves in a metal. Conduction electrons in a metal form a very uniform high density plasma exhibiting longitudinal plasma oscillations.’ Typical conduction electron densities are of order 1O22 cmB3 corresponding to a maximum gradient of order lOO’GV/cm. Although this gradient equals lo3 V/A, *Work supported by the Department of Energy, contract DE-AC03-76SF00515. Invited talk presented at the Symposium on Advanced Accelerator Concepts, Madison, Wisconsin, August 21-27, 1986