Implementation of the α-CHERS diagnostic for D–T operation of TFTR

The α-CHERS diagnostic is a high throughput charge exchange recombination spectroscopy diagnostic designed to measure the density profile and time evolution of 0–500 keV alpha particles during D–T operation of the Tokamak Fusion Test Reactor (TFTR). Following successful tests with a prototype α-CHERS system, an improved, multichannel system has been installed for D–T operation. Three spatial channels may be observed simultaneously, and the spectral resolution of 0.5 nm permits increased alpha energy resolution and improved impurity line identification. More efficient coupling optics between the spectrometer and charge coupled device (CCD) detectors have increased the light throughput, and radiation shielding has been installed around the detectors and spectrometers to eliminate the neutron/gamma-ray noise observed in high power D–D plasmas.