Control of the spectrum of MeV electrons accelerated in laser plasma of nitrogen clusters

The influence of the sizes of nitrogen clusters on the spectrum of MeV electrons accelerated in a cluster laser plasma under the influence of 5 TW femtosecond laser pulses has been studied. For this task, an electronic magnetic spectrometer was developed and created for the energy ranges: 0.3 – 5 MeV, or 1 – 10.5 MeV. The measured electronic spectra consist of a quasi-monoenergetic peak at 0.4±0.1 MeV, a broad “peak” at 2-3 MeV with an exponential tail with a temperature T = 3±1 MeV. It is shown that the maximum injection of electrons into the accelerating wave is achieved for clusters with an average radius corresponding to the Coulomb explosion limit. The electron bunch was the sum of collimated (10 mrad) and divergent (≈100 mrad) beams with maximum energies up to 10 MeV, which may indicate a hybrid acceleration mode.