A practical self-healing mercury target for efficient generation of soft x-ray radiation

We have developed a self-healing mercury-wetted target as a practical source of soft x-ray radiation for photoexciting extreme ultraviolet lasers. A threaded rod, rotating in a pool of mercury, demonstrates a soft x-ray conversion efficiency similar to that of expendable gold-coated targets in synchronous photopumping of a photoionization Xe2+ laser at 109 nm. Surfaces self-heal or are continuously regenerated by rewetting, while mercury debris is removed by evaporation from the target chamber walls and optics. Long target lifetime and self-cleaning performance of the new target system are attractive features in future high-repetition-rate, high-throughput applications for photopumping of extreme ultraviolet or soft x-ray lasers, and more generally as incoherent sources for soft x-ray lithography and spectroscopy.