Demonstration of a 1 mW average power, 7 Hz table-top soft X-ray laser

Summary form only given. Important motivations for the development of high average power table-top sources of coherent soft X-ray radiation can be found in applications belonging to several disciplines of science and technology. To date, the leading sources of high average power coherent soft X-ray radiation have been undulators in modern storage rings, so-called third generation synchrotrons. High average power beams of soft X-ray coherent radiation can in principle also be generated with much more compact devices using either nonlinear optical techniques for frequency up-conversion of optical laser radiation, or the direct amplification of spontaneous emission in a plasma (an X-ray laser). Soft X-ray lasers have the advantage of a high energy per pulse and therefore the potential to produce very high average power. Soft X-ray lasers pumped by large optical lasers of the type used in fusion research have generated output pulse energies of up to several mJ but are limited to a repetition frequency of only a few pulses per hour at best. We report a 2 to 3 orders of magnitude increase in the average power of table-top soft X-ray lasers.