X-ray spectrometer configuration, throughput and data treatment over the JET DTE2 and DTE3 Camapigns
The calibration of the JET x-ray spectrometer is presented. The absolute throughput, diffractor focussing and instrument function of the spectrometer is presented and the quality of the ion temperature measurement is re-assessed, particularly at the lower end. The addition of a second diffractor enables simultaneous measurements of the spectra from H- and He-like nickel which widens the spatial coverage of the core-ion temperature measurements for high-performance plasmas at a fixed Bragg angle range.\ A calculation of the absolute continua from the spectrum background from the second diffractor is analysed for different JET plasmas. The spectrometer’s narrow bandwidth makes it ideal as an “x-ray monochromator” that can sample a single energy channel (or two over the two crystal orders) within the free-free and free-bound x-ray continua. The measurable effect for impurity-seeded plasmas is explored as a means to determine the plasma concentration of the seeding impurities which has the potential to be a robust method for high performance DT operations in reactor-class machines.