Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

Abstract

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X-ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal (200) (2d = 0.4027 nm) is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shenguang-II which can deliver laser energy of 60–80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1s2p ¹P₁-1s²¹S₀ resonance line(w), the 1s2p ³P₂-1s²¹S₀ magnetic quadrupole line(x), the 1s2p ³P₁-1s²¹S₀ intercombination lines(y), the 1s2p ³S₁-1s²¹S₀ forbidden line(z) in helium-like Ti X XI and the 1s2s2p ²P_3/2-1s²2s ²S_1/2 line(q) in lithium-like Ti X X have been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution(λ/Δλ) is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.

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