title: Characteristics of a cylindrical collector mirror for laser-produced xenon plasma soft X-rays and improvement of mirror lifetime by buffer gas.
abstract: The focusing characteristics of a ruthenium-coated cylindrical mirror were investigated on the basis of its ability to collect and focus broadband 5-17-nm soft X-rays emitted from a laser-produced plasma. Based on the plasmas spectral intensity distribution and the reflectivity function of the mirror, we defined the optimum position of the integrated cylindrical mirror at which the X-ray energy flux transported and focused through the mirror was maximum. A minimum spot diameter of 22 mm at a distance of approximately 200 mm from a soft X-ray source was confirmed. The maximum intensity of the collected soft X-rays was 1.3 mJ/cm(2) at the center of the irradiation zone. Thus, the irradiation intensity was improved by approximately 27 times when compared to that of 47 μJ/cm(2) without the mirror. The debris sputtering rate on the reflection surface of the mirror can be reduced to 1/110 by argon gas at 11 Pa, while the attenuation rate of the soft X-rays due to absorption by the buffer gas can be suppressed to less than 10% at the focal point. The focusing property of the mirror is expected to be maintained for 3000 h or longer without significant degradation for a 100 W/320 pps laser shot if the ruthenium layer is thicker than 10 μm. These results suggest that a stand-alone broadband soft X-ray processing system can be realized by using laser-produced plasma soft X-rays.
authors.affiliation: Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 678-1205, Japan. t-inoue@lasti.u-hyogo.ac.jp
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Inoue
authors.forename: Takayasu
authors.initials: T
authors.lastname: Mochizuki
authors.forename: Shuji
authors.initials: S
authors.lastname: Miyamoto
authors.forename: Kazuya
authors.initials: K
authors.lastname: Masuda
authors.forename: Sho
authors.initials: S
authors.lastname: Amano
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kanda