Adaptive system for wavefront correction based on 240-mm bimorph deformable mirror and Shack-Hartmann wavefront sensor is presented. The dynamic characteristics of the deformable mirror and the performance of the wavefront correction in various operating modes of the PEARL facility as well as the features of phase distortion compensation in a single-shot generation regime are studied. An improvement in the quality of focusing that led to an increase in the Strehl ratio to 0.6 is demonstrated.
We present the results of the investigation of a Nd:glass rod laser amplifier 320 mm long and 150 mm in diameter. The gain and depolarization distributions over the amplifier aperture as well as the stored energy have been measured for different values of the pump energy. The small signal gain averaged over the rod aperture was 2.3 when the pump energy was 48 kJ. The corresponding stored energy was 500 J. We have determined the maximal pulse repetition rate that is quiet safe from the point of the thermal shock damage. It is about 1 shot per 5 minutes. The calculated focal length of the thermal lens exceeds 1.5 km in such a regime. We have shown that the use of a couple of such amplifiers gives the possibility to increase the energy of laser pulses up to 650 J.
The work covers a series of laser wakefield acceleration (LWFA) experiments carried out at the petawatt laser PEARL
(PEtawatt pARametric Laser, Nizhny Novgorod, Russia). The use of different focusing angles and gas jets of various
sizes is discussed. Modulation of the gas jet concentration profile for electron trapping improvement has been studied in
experiments. Specific singe-shot laser-plasma interaction diagnostics adapted for low repetition rate systems with low
output parameter stability, as well as a two-screen magnetic spectrometer with advanced accuracy of spectral
measurements of electron bunches are considered.
In this paper we discuss laser wake field acceleration experiments made at the PEtawatt pARametric Laser (PEARL).
Using free 2mm and 5 mm gas jet without preplasma we generated electron beam with energy up to 260 MeV. The
charge of quasimonoenergetic beams achieved 300 pC, angular divergence 0.2 degree. The special attention is paid for
diagnostics which is adapted for low repetition rate systems with low output parameters stability.