Enhanced Isochoric Heating from Fast Electrons Produced by High-Contrast, Relativistic-Intensity Laser Pulses

Thin, mass-limited targets composed of V/Cu/Al layers with diameters ranging from 50 to 300  μm have been isochorically heated by a 300 fs laser pulse delivering up to 10 J at 2×1019  W/cm² irradiance. Detailed spectral analysis of the Cu x-ray emission indicates that the highest temperatures, of the order of 100 eV, have been reached when irradiating the smallest targets with a high-contrast, frequency-doubled pulse despite a reduced laser energy. Collisional particle-in-cell simulations confirm the detrimental influence of the preformed plasma on the bulk target heating.