Vertical high-resolution Bragg x-ray spectrometer for the tokamak fusion test reactor

Abstract

A Bragg x-ray spectrometer of high spectral resolution (λ/Δλ=10 000–20 000) which accommodates three crystals and position-sensitive detectors in the Johann configuration has been installed in the diagnostic basement of the tokamak fusion test reactor (TFTR) for the measurement of radial ion temperature profiles. The ion temperature is derived from the Doppler broadening of Kα-resonance lines of metal impurity ions, e.g., Ti, Cr, Fe, and Ni, in the helium-like and hydrogen-like charge states. The x-ray diffraction plane is almost perpendicular to the magnetic axis, but slightly tilted by an angle of 3.8°, which makes it possible to measure poloidal and toroidal plasma rotation velocities of vΘ>5×103 m/s and vΦ>1×105 m/s, from the Doppler shift of spectral lines. Results obtained from the observation of TiXXl Kα-line spectra with a 220-silicon crystal of a 2d spacing of 3.8400 Å and a curvature radius of 11.05 m are reported.