Efficient Generation of X-Ray Radiation under Relativistic Laser Pulses Interaction with a Kr Cluster Jet

X-ray generation under interaction of relativistic laser pulses with krypton clusters has been studied. It is shown that the optimal focusing points for generating characteristic and hard bremsstrahlung are located in regions with different cluster concentrations inside the gas jet. A record (4.2 × 10 –6 ) conversion efficiency of relativistic laser pulses into characteristic K α (12.6 keV) has been achieved under interaction with large krypton clusters. The bremsstrahlung plasma temperature has been measured to be T e = 6 keV at an integral energy of the X-ray pulse of 3 × 10 9 keV/(4π pulse). The application of the designed source in time-resolved X-ray studies and in radiobiology are discussed.