Efficient high-repetition-rate fs-laser based X-ray source

The generation of [ Fe]Kα line radiation has been studied on a compact, ultrashort, laser based hard X-ray source, particularly suited for high-repetition-rate laser systems (1 to >10 kHz). Sub-millijoule, 25 fs Ti:sapphire laser pulses are applied to generate hard X-ray radiation on a commercially available ferric audio cassette tape target. Spectroscopic investigations reveal strong iron K α emission in addition to a weak bremsstrahlung continuum. Under single exposure and single pulse conditions the X-ray yield is low. Energy conversion efficiencies of about ηK α=2×10-7 are observed. Prepulse and multiple shot exposure techniques, both successfully used with high energy/low repetition rate systems, are investigated for these low energy/high repetition rate conditions. Depending on the applied pulse energy and intensity, the X-ray yield can be enhanced by more than three orders of magnitude. Photon fluxes exceeding 2×109 K α photons/s are generated with the presented tape target yielding conversion efficiencies of nearly ηK α=10-5.