High-throughput, high-resolution soft X-ray crystal spectrometer for Tokamak-plasma studies

A Johann-type reflection spectrometer with a wavelength resolution of 15000 at 0.229 nm (CrK_alpha ) is described. The diffracting crystal is a (310)-quartz plate with 50*30 mm² total and useful area, bent to a radius of 1380 mm. The use of a novel, simple crystal bending device and of a position-sensitive proportional counter makes this instrument interesting also for other domains of X-ray spectroscopy. Results of extended calculations on diffraction properties of quartz as a function of diffraction plane index and wavelength are also presented.