Laser Plasma Soft X‐Ray Source in the Water Window Based on Cryogenic Targets

Abstract

SUMMARYTo generate continuously repetitive soft X-ray pulses in the water window from laser-produced plasmas, a onedimensionally translating substrate system with a closed He gas cryostat that can continuously supply various cryogenic targets has been developed. The system was successfully operated at a lowest temperature of 15 K and at a maximum up-down speed of 12 mm/s. Solid Ar and N 2 layers were formed, and the water-window spectra from them were studied. The emission intensity from Ar was found to be about eight times stronger than that from N 2 . Developed laser-plasma source demonstrated high average power of 140 mW in the water-window soft X-ray, when a commercial Nd:YAG Q-switched laser was used to irradiate a solid Ar target with energy of 1 J at a repetition rate of 1 Hz. It can be used for various applications, including soft Xray microscopy, in place of synchrotron facilities. C⃝ 2017 Wiley Periodicals, Inc. Electron Comm Jpn, 101(1): 55-60, 2018; Published online in Wiley Online Library (wileyonlinelibrary.com).