Relativistic self-focusing

Laser intensities of order and above 0.001 times the relativistic intensity I/sub rel/ coupled with ionized target electron number densities close to and above the laser cutoff density n/sub ec/ exhibit sudden relativistic self-focusing, with attendent beam converging lengths about equal to the diameter of the initial vacuum laser beam. The analytical model is a relativistic generalization, including mass and energy effects, of the plasma electron-ion collision process, combined with a local bending of the laser beam wave front resulting from influences on the plasma refractive index. Dependences on the plasma temperature, degree of ionization and instabilities, as given by an effective collision frequency, are studied. Self-focusing and dielectric swelling results in maximum oscillation energies in agreement with several high intensity experiments. The wavelength independence of electron energy, as shown in the recent experiments of G.H. McCall, as well as measured MeV ion emission from irradiated targets, can be explained by the model. It is concluded that Nd glass laser beams of 1014 watts power will generate dense plasmas containing highly charged heavy ions with maximum energies approximately 20 GeV