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22Complex Systems of Charged Particles and their Interactions with Electromagnetic Radiation 2019
FAST PARTICLES GENERATION IN INTENSE LASER-PLASMA
INTERACTIONS
N.E. Andreev
Joint Institute for High Temperatures of the Russian Academy of Sciences, Moscow, Russia,
e-mail: nikolay. e.andreev@gmail.com
A.Ya. Faenov made a great contribution into the development and application of X-ray spectroscopy in very different fields of science, in particular, for determining the energy spectra of particles accelerated by a laser. His innovative results on the non-adiabatic plasma heating created by the ionization of a gas by the optical field of a short intense laser pulse; in the observation of fast ions produced by the interaction of a femtosecond laser pulse with clusters, and also by the interaction of nanosecond-long laser pulses with a large-scale laser plasma, are well known over the world and rendered outstanding impact on the development of methods for the diagnostic of the laser produced plasmas.
Nowadays, spectroscopic methods play an important role in the analysis of a wide range of experiments from the interaction of moderate-intensity nanosecond laser pulses with matter to the relativistic-intense interaction of femtosecond laser pulses with plasma. In view of current and future experiments, various methods of electron acceleration in plasma are discussed. Spectra of multi-charged ions are widely used for determination of the bulk electron temperature and density, as well the energy and fraction of hot electrons. These parameters are of crucial importance for characterization of laser-matter interaction process that strongly depends on a laser pulse contrast and a laser frequency. It was shown that at high contrast relativistic laser-matter interaction, it is possible to generate a thin layer of keV hot near-solid density plasmas of sub Gbar pressure [1]. Here bulk electrons play a major role in the target heating process. This scenario is opposite to the volumetric character of the energy deposition produced by supra-thermal electrons that is usual for relativistic laser interaction with plasma corona produced by the laser pre-pulse.
Effective direct laser acceleration of electrons to energies that go far beyond the limits predicted by Wilkes scaling can be achieved in a plasma with an electron density close to critical (NCD). A hydrodynamically stable NCD plasma can be generated by a supersonic ionization mechanism, when a well-defined separate ns pulse is sent to a target of low-density CHO foam, ahead of the relativistic main pulse. The resulting well-collimated high-energy electron beams reach effective temperatures 6-7 times higher than the ponderomotive ones, and carry charges of hundreds of nC [2].
Acceleration of electrons to high energies with a large acceleration gradient, far exceeding that available in conventional radio frequency accelerators, can be achieved in a multi-stage laser wakefield accelerator, operating in a moderately non-linear mode. The effect of synchrotron radiation on the dynamics of energy gain and spin precession of a polarized electron beam is investigated in the process of acceleration at the self-consistent description of the nonlinear dynamics of a laser pulse and the generated accelerating and focusing plasma wake fields. It is shown that synchrotron radiation hardly affects the energy gain and polarization of the electrons, which are accelerated in wakefields characteristic of the moderately nonlinear mode of laser-plasma acceleration up to an energy of 4 TeV [3].
References
[1] O.N. Rosmej, Z. Samsonova, S. Hofer et al. 2018 Physics of Plasmas 25, 083103; doi: 10.1063/1.5027463.
[2] O.N. Rosmej, N.E. Andreev, S. Zaehter et al. 2019 New Journal of Physics https://doi.org/10.1088/1367-2630/ab1047.
[3] D.V. Pugacheva, N.E. Andreev 2018 Quantum Electronics 48 (4) 291 - 294.
