RAMAN BACKSCATTERING IN LASER WAKE-FIELD AND BEAT-WAVE ACCELERATORS

An intense short laser pulse propagating through a plasma undergoes stimulated Raman backscattering when oscillatory electron velocity upsilon-0 greater-than-or-equal-to 4c/(2-omega-0-tau-0-omega-p-tau-0)1/2, where omega-0 and tau-0 are the frequency and pulse duration of the laser and omega-p is the plasma frequency. In a laser wake-field accelerator employing short laser pulses with omega-p-tau-0 approximately 2-pi, this threshold is exceeded when upsilon-0/c greater-than-or-approximately-to 0.1. The threshold is smaller in a beat-wave accelerator where longer pulses are used.