Electron acceleration up to MeV level under nonlinear interaction of subterawatt femtosecond laser chirped pulses with Kr clusters

摘要： The acceleration of electrons to MeV energies from a Kr cluster jet irradiated by a relativistic (6 × 1018 W cm?2) femtosecond laser pulse is studied. For the first time, the action of transform-limited laser pulse effects on the generation of hot electrons with an effective temperature (Thot) of around 150 keV is experimentally demonstrated. The particles were accelerated in the plasma channel formed under self-focusing of the laser beam. Introducing a linear positive chirp together with pulse elongation from 50–~120 fs results in substantially enhanced hot electrons flux with a growth of Thot up to 300 keV and a maximal energy of over 2 MeV. The observed effect may be related to the strongly nonlinear propagation of the pulse through plasma, accompanied by more favorable conditions for efficient particles energy gain and pulse nonlinear compression.