Author:

Keywords:

Science & Technology, Physical Sciences, Physics, Fluids & Plasmas, Physics, FAST-ELECTRON TRANSPORT, HIGH-INTENSITY LASER, SOLID TARGETS, PLASMA, ION, RADIATION, ALUMINUM, BEAMS, POWER, 0201 Astronomical and Space Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, 0203 Classical Physics, Fluids & Plasmas, 5106 Nuclear and plasma physics, 5109 Space sciences

Abstract:

Results are presented from laser–plasma interaction experiments using the VULCAN laser at the Rutherford Appleton Laboratory. Wire targets were used to elucidate the role of the return currents generated by the relativistic electron beam leaving the target at laser intensities up to 5 3x10^19 W/cm^2. For some shots an additional wire or a foil was placed near the target wire. In other shots, a foil was used as the target with a wire behind. Three main observations were made: i) Z-pinch behavior in the wires due to the return currents, ii) optical transition radiation (OTR) at the second harmonic of the laser, and iii) proton emission. The OTR and the proton emission were observed from both the primary wire target and the adjacent wire. The OTR emission is associated with electron bunches at twice the laser frequency due to ponderomotive JxB acceleration by the laser. The proton emission from the adjacent target was likely due to field emission of electrons by the large potential produced from charging of the primary wire target. The observations agree with simulations using the three-dimensional tree code PEPC and the two-and-one-half-dimensional particle-in-cell code OSIRIS.