The acceleration of charged particles and the upshift of the frequency of short wave packets of laser radiation are discussed. The acceleration and the upshift are caused by plasma waves excited by a strong laser pulse in a nonuniform plasma. It is proved that, by a proper choice of the plasma density profile, it is possible to increase the efficiency of the particle acceleration and of the upshift of the wave packet frequency. It is also shown that unlimited acceleration of charged particles is possible for specific spatial dependences of the plasma density. In this unlimited acceleration regime, particles have a fixed phase relationship with respect to the plasma wave, as their energy increases with time. When the wave-breaking limit is approached and surpassed, the efficiency of the acceleration of the charged particles and of the frequency upshift of the photons can be increased significantly. This is due both to the excitation, in the nonstationary wake behind the laser pulse, of an electric field larger than that produced by a steady plasma wave, and to the rapid electron density variations that occur when the wave breaks.
Charged Particle and Photon Acceleration by Wake Field Plasma Waves in Nonuniform Plasmas
PEGORARO, FRANCESCO;
1993-01-01
Abstract
The acceleration of charged particles and the upshift of the frequency of short wave packets of laser radiation are discussed. The acceleration and the upshift are caused by plasma waves excited by a strong laser pulse in a nonuniform plasma. It is proved that, by a proper choice of the plasma density profile, it is possible to increase the efficiency of the particle acceleration and of the upshift of the wave packet frequency. It is also shown that unlimited acceleration of charged particles is possible for specific spatial dependences of the plasma density. In this unlimited acceleration regime, particles have a fixed phase relationship with respect to the plasma wave, as their energy increases with time. When the wave-breaking limit is approached and surpassed, the efficiency of the acceleration of the charged particles and of the frequency upshift of the photons can be increased significantly. This is due both to the excitation, in the nonstationary wake behind the laser pulse, of an electric field larger than that produced by a steady plasma wave, and to the rapid electron density variations that occur when the wave breaks.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
