Abstract
3D particle-in-cell (PIC) simulation is used to study bulk stochastic heating of a cluster (dust, droplet) plasma containing submicrometer particles of heavy atoms (gold) upon irradiation of the cluster medium by an ultrashort (15 fs) laser pulse of moderately relativistic intensity ( \( \gtrsim \) 1018 W/cm2). Characteristics of the short X-ray pulse generated mainly due to the bremsstrahlung effect are obtained. Contribution of X‑ray radiation of synchrotron type emitted by electrons with trajectories of stochastic walks between clusters to the radiation yield is discussed. Generation of hard X-ray bremsstrahlung is caused by the appearance of a well-pronounced high-energy plateau, or tail, in the distribution function of the laser-heated electrons. Calculated conversion coefficient to the broadband X-ray radiation for the microcluster medium exceeds 10–5, which allows the cluster medium to compete with the solid targets while having an advantage when used with the lasers emitting high-contrast pulses at a high repetition rate.
