Soft X-ray conversion efficiencies in a 5–17 nm wavelength range in xenon and tin plasmas produced by a 1.06 µm Q-switched neodymium-doped yttrium aluminum garnet laser were investigated. They were measured to be 25 and 20% for the xenon and tin plasmas, respectively at a laser intensity of about 2×1010 W/cm2. These results indicate that a stand-alone soft X-ray source using a laser-produced xenon or tin plasma is useful for various applications that require intense, soft X-ray photons in a wide wavelength range.

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Mitigation of fast debris and soft x-rays generated from laser-produced xenon plasmas were studied in an argon buffer gas in laser intensities of 10 9 -10 11 W cm −2 using a cryogenic drum target. Considerable mitigation of debris was confirmed by measurements of material sputtering. From the experimental results, an attenuation parameter of sputtering by the debris σ1 and an absorption cross section of soft x-rays at 13.5 nm σ 2 (13.5 nm) were derived to be 2.2 × 10 −20 m 2 and 1.8 × 10 −22 m 2 , respectively. Moreover, σ1 is concluded to be equivalent to the effective collision cross section σ 1 of a debris particle at kinetic energy of 1-4 keV. Sufficient debris mitigation can be obtained together with low soft x-ray absorption (less than 10%). These parameters provide a useful design tool for realizing a practical soft x-ray source because they predict the effect of the buffer gas well.

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