ABSTRACT
Abstract. We combine near-field imaging with the recently developed technique of picosecond x-ray laser interferometry to probe the plasma conditions in which the Ni-like Pd transient collisional x-ray laser is generated and propagates. We observe a strong dependence of the laser pump parameters on the effective laser-gain medium coupling. The most effective coupling of laser pump energy occurs when the duration of the main heating pulse is comparable to the gain lifetime (~10ps for mid-Z Ni-like schemes). This can increase the output intensity by more than an order of magnitude relative to the case were the same pumping energy is delivered within a shorter heating pulse duration (< 3ps). The higher intensity heating pulses are observed to be absorbed at higher electron densities and in regions were steep density gradients limit the effective length of the gain medium.
