Absolute soft x-ray calibration of laser produced plasmas using a focusing crystal von Hamos spectrometer
Absolute x-ray calibration of laser-produced plasmas was performed using a focusing crystal von Hamos spectrometer. The plasmas were created by an Nd-YAG laser (0.53 μm/200 mJ/3 ns/10 Hz) on massive solid targets (Mg, Cu, Zn, Sn, Mo, Ta, Ti, Steel). Cylindrical mica crystal (radius of curvature R=20 mm) and a CCD linear array detector (Toshiba model TCD 1304AP) were used in the spectrometer. Both the mica crystal and CCD linear array were absolutely calibrated in the spectral range of λ=7 - 15 Å. The spectrometer was used for absolute spectral measurements and the determination of the plasma parameters. The unique target design allowed for multiple instruments to observe the plasma simultaneously which improved analysis. High spectrometer efficiency allows for the monitoring of absolute x-ray spectra, x-ray yield and plasma parameters in each laser shot. This spectrometer is promising for absolute spectral measurements and for monitoring laser-plasma sources intended for proximity print lithography.
Weeks, T; Harrison, M; Johnson, M; Shevelko, AP; Ellsworth, J; Bergeson, S; Asplund, M; Knight, LV
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