Isochoric heating with intense proton beams driven by multi-picosecond pulse laser and its measurement with time-resolved K-alpha emission spectroscopy

Proton beams provide a unique means to heat a target isochorically. With this promising characteristic, short-pulse laser-driven proton beams have been studied for potential applications that require a rapid heating source. However, time-resolved measurement of target heating with proton beams has largely remained unexplored in the experiments. Here, we present an analysis of the time-resolved K-alpha spectroscopy measurements of proton-heated copper solid sample using the High-Resolution streaked X-ray Spectrometer (HiResSpec). In the experiment, the OMEGA-EP short pulse laser with an energy of up to kJ and pulse duration of up to 10 ps was focused onto a target (partial hemisphere with cone structure) to generate and focus a proton beam. HiResSpec diagnosed the Cu K-alpha line emission spectra. The high temporal and spectral resolutions (~2ps and <2eV) allowed to observe shifts in the lines’ positions that are dependent on the sample’s temperature. The temperature evolution (over 50 eV within 30 ps) was found to be consistent in hybrid particle-in-cell simulations encompassing various aspects, including proton acceleration, focusing, transport, and target heating. Detailed results including experimental measurements and simulation approaches will be presented.