High repetition rate table-top soft X-ray lasers in capillary discharges and laser-created plasmas

We discuss very recent advances in high repetition rate soft x-ray lasers resulting from the use of two different types of hot dense plasmas: fast capillary discharges and laser-created plasmas. We have demonstrated a new high repetition rate 46.9 nm capillary discharge laser that fits onto the surface area of a small desk and that operates at a relatively low voltage, therefore not requiring a Marx generator. Laser pulses with an energy of ∼ 13 μJ are generated at repetition rates up to 12 Hz. About (2-3)×10 ⁴ laser shots can be generated with a single capillary. This new type of portable laser is an easily accessible source of intense short wavelength laser light for applications. We also discuss the demonstration of 5 Hz repetition rate table-top soft x-ray lasers producing microwatt average powers at wavelengths ranging from 13.2 to 33 nm. The results were obtained by collisional electron excitation of Ni-like and Ne-like ions in plasmas efficiently heated with a picosecond optical laser pulse impinging at grazing incidence onto a pre-created plasma. Efficient deposition of the pump beam into the gain region allows for the excitation of soft x-ray lasers in this wavelength range with a short pulse pump energy of only 1 J.