Optimal main pulse angle for different preplasma conditions in transient collisionally pumped x-ray lasers

The effects of the incidence angle of the main pump (MP) pulse in non-normal pumping geometry and the influence of the MP duration are investigated experimentally and theoretically for a transient collisionally pumped (TCE) x-ray laser in Ni-like Zr at 45 degrees and 72 degrees incidence angle on the target. The way they transfer to the x-ray laser output depends on the preplasma conditions, most notably on the average ionization distribution at the arrival of the MP. Moreover, contrary to previous grazing incidence pumping results, it is found that the shortest attainable MP maximizes the output. Modeling of the experimental results is performed with EHYBRID code. The results are important for scaling high repetition-rate non-normal incidence pumped lasers to sub- 10nm wavelengths.