SPRED spectrograph upgrade: High-resolution grating and improved absolute calibrations

Abstract

Two improvements to the SPRED multichannel VUV spectrographs used on the TFTR and PBX tokamaks have been made: (1) a new 2100-g/mm grating covering the 100-320-Å region with 0.4-Å resolution (FWHM) has been added to the existing 450-g/mm grating (100-1100 Å with 2-Å resolution), and (2) the TFTR SPRED has been absolutely calibrated using synchrotron radiation from the NBS SURF II facility, while the PBX system has been calibrated using conventional branching ratios along with line ratios from charge-exchange- recombination excited lines. The availability of high-resolution spectra in the 100-320-Å range provides improved measurements of metallic ion emissions and, when the instrument views across a neutral beam as in PBX, allows carbon and oxygen densities to be measured via charge-exchange-recombination spectroscopy.