No abstract

The three-dimensional evolution of a short laser pulse is considered. The linear stability analysis that takes account of the scattered light convection and predicts a development of pulse modulation at the electron plasma frequency, is carried out. It is demonstrated that a laser pulse with a power above or close to the critical, which is required to provide a pulse relativistic self-focusing, undergoes compression and self-modulation in the course of self-consistent pulse evolution and, as a result, resonant excitation of an extremely strong plasma wave occurs. It is shown that for a properly taken initial pulse and plasma parameters it is possible to obtain a wake field of an extremely high intensity for a fairly long time to provide a new promising outlook for the laser accelerator concept. The influence of plasma inhomogeneity and pulse initial focusing on the considered self-resonant plasma wave excitation is studied.

The upgraded Accelerator Test Facility (ATF) CO 2 laser located at Brookhaven National Laboratory offers a unique opportunity to investigate laser wakefield acceleration (LWFA) with a 10:6-m laser, a wavelength where little experimental work exists. While long laser wavelengths have certain advantages over short wavelengths, our modeling analysis has uncovered another important effect. The upgraded ATF CO 2 laser will have a pulse length as short as 2 ps. At a nominal plasma density of 10 16 cm ÿ3 , this pulse length would normally be considered too long for resonant LWFA, but too short for self-modulated LWFA. However, our model simulations indicate that a well-formed wakefield is nevertheless generated with electric field gradients of E z * 2 GV=m assuming 2.5 TW laser peak power. The model indicates pulse steepening is occurring due to various nonlinear effects. It is possible that this intermediate laser pulse length mode of operation may permit the creation of well-formed, regular-shaped wakefields, which would be needed for staging the LWFA process. Discussed in this paper are the model, its predictions for an LWFA experiment at the ATF, and the pulse steepening effect.

It is demonstrated that in an underdense plasma the process of three-dimensional evolution of the short and strong laser pulse with duration about several plasma periods leads to the compression and self-modulation of the , could not be prevented from diffraction as the nonlinear refraction does not compensate the progressing "blow off" of 0-8194-1 162-0/931$6.OQ