Radiative losses in plasma accelerators
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AL, NONLINEAR, AND SOFT MATTER PHYSICS
Radiative Losses in Plasma Accelerators I. Yu. Kostyukova,*, E. N. Nerushb, and A. M. Pukhovc a
Institute of Applied Physics, Russian Academy of Sciences, ul. Ul’yanova 46, Nizhni Novgorod, 603950 Russia b Nizhni Novgorod State University, Nizhni Novgorod, 603950 Russia c University of Düsseldorf, Düsseldorf, 40225 Germany * e-mail: [email protected] Received March 7, 2006
Abstract—We investigate the dynamics of a relativistic electron in a strongly nonlinear plasma wave in terms of classical mechanics by taking into account the action of the radiative reaction force. The two limiting cases are considered. In the first case where the energy of the accelerated electrons is low, the electron makes many betatron oscillations during the acceleration. In the second case where the energy of the accelerated electrons is high, the betatron oscillation period is longer than the electron residence time in the accelerating phase. We show that the force of radiative friction can severely limit the rate of electron acceleration in a plasma accelerator. PACS numbers: 52.38.Kd, 41.60.-m DOI: 10.1134/S1063776106110173
1. INTRODUCTION New acceleration methods that provide a high rate of energy gain by particles are currently being developed to generate charged particles with very high energies. One of the promising methods is the acceleration of charged particles in a plasma wave excited by a short intense laser pulse or a dense bunch of relativistic electrons [1–4]. The longitudinal electric field in a plasma wave can reach huge strengths. Such a field is capable of accelerating electrons to very high energies. Recently, substantial progress has been made in generating short quasi-monoenergetic beams of ultrarelativistic electrons in laser plasma [5]. One of the models [6, 7] that describe the generation of a quasimonoenergetic beam of ultrarelativistic particles suggests that this generation is associated with the transition to a strongly nonlinear regime of laser pulse– plasma interaction. In this regime, the periodic plasma wave in the wake of a laser pulse transforms to a plasma cavity without electrons. Plasma electrons, along with external beam electrons, can be trapped by the cavity and accelerated to very high energies. It should be noted that, apart from a strong accelerating electric field, significant focusing transverse fields act on the electrons. These forces may be comparable in intensity to the accelerating force. The action of the focusing forces leads to the excitation of betatron electron oscillations across the acceleration direction. As a result of these oscillations, the relativistic electrons intensely emit electromagnetic waves [8]. Just as in conventional accelerators, the losses through radia-
tion can greatly reduce the electron acceleration efficiency in a plasma cavity. Since the properties of the electromagnetic radiation from an electron are determined mainly by the action of the focusing forces, when these properties are studied, the action of the accele
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