Abstract:
The existing theory of relativistic self-focusing is extended to electron densities ne close to and above the cutoff density nec. It is shown that relativistic self-focusing is possible at densities ne≤nec for laser intensities of the order of 10-3 times the relativistic intensity of 3.66×1018 W/cm2 for an Nd glass laser. Additionally, very-short-range self-focusing is predicted over distances of the order of the initial beam diameter. The lowest threshold intensity is calculated and its dependences on the plasma temperature and ionization number are found. The increase in the effective collision frequencies due to instabilities is evaluated.