Electron and proton acceleration in superstrong laser field: Simulations and models
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ICLE ACCELERATION IN PLASMA
Electron and Proton Acceleration in Superstrong Laser Field: Simulations and Models S. N. Andreeva and V. P. Tarakanovb a
Prokhorov Institute of General Physics, Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119991 Russia b Joint Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya ul. 13/19, Moscow, 127412 Russia Received February 17, 2009; in final form, June 5, 2009
Abstract—Results of particleincell simulations of the interaction of an intense femtosecond laser pulse with a thin aluminum foil the front surface of which is covered with a hydrogen preplasma layer are compared with predictions of simple analytical models. It is shown that light pressure may be the most efficient mech anism for proton acceleration in the initial stage of laser–plasma interaction. PACS numbers: 52.38.Kd, 41.75.Jv DOI: 10.1134/S1063780X09120034
1. INTRODUCTION The problem of charged particle acceleration in the interaction of intense laser pulses with targets of differ ent shapes and compositions has been thoroughly studied both experimentally and theoretically (see, e.g., [1–3] and references therein). In these studies, considerable attention has been paid to determining the optimal parameters of laser pulses and targets that are required to increase the energy of charged particle beams and improve their quality. The most widespread and informative method for theoretically studying the interaction of pico and femtosecond laser pulses with plasma is particlein cell (PIC) simulations. In many papers, along with numerical simulations, simple analytical models of laser–plasma interaction have also been considered. These models allow one, in particular, to estimate the contribution of different physical mechanisms to the process of laser acceleration of charged particles and, thus, better understand simulation results and laser– plasma processes as a whole. In this paper, results of PIC simulations of the interaction of an intense femtosecond laser pulse with a metal target the front surface of which is covered with a hydrogen preplasma layer (a situation rather fre quently encountered in laser–plasma experiments) are compared with predictions of simple analytical models. It is shown that these models allow one to cor rectly estimate the main parameters of accelerated charged particles and describe their dynamics over a relatively long time interval.
2. FORMULATION OF THE PROBLEM The interaction of a femtosecond laser pulse with a metal target was simulated on a personal computer (PC) by using a twodimensional (2D) version of the KARAT relativistic electrodynamic PIC code [4]. An important advantage of the code is a developed graph ical interface that allows one to preanalyze the results in the course of simulations. The main constraint on PIC simulations performed using a PC is the number of particles, which, at present, cannot considerably exceed 107. For this reason, in formulating the prob lem, certain limitations were imposed on the target parameters and the dime
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