X-ray imaging crystal spectrometer on EXL-50U spherical torus

An X-ray imaging crystal spectrometer (XCS) has been implemented on the EXL-50U spherical torus to provide spatially resolved measurements of the ion temperature (Ti) and relative toroidal rotation velocity (ΔVt). These parameters are inferred from the He-like argon (Ar XVII) spectrum. By utilizing the imaging properties of a spherically bent crystal, the system diffracts and focuses plasma emission onto a pixel array detector (PILATUS3 300K) based on the Rowland-circle geometry, enabling the simultaneous acquisition of spectral and spatial information. The experimental setup and initial results are presented, demonstrating a pronounced Ti increase after the onset of neutral beam injection (NBI). Preliminary ion temperature profiles obtained from the experimental measurements are also discussed.