A spectroscopic system for time- and space-resolved studies of impurities on the EXTRAP-T2 reversed field pinch

The radial distribution of impurity line emission in the EXTRAP-T2 reversed field pinch (RFP) is studied with a five viewing chord, absolutely calibrated, spectrometer system. The light is analyzed with a single 0.5 m grating spectrometer. Different parts of the entrance slit are used for different channels. This arrangement makes it possible to use the system over a wide wavelength range, from 2500 to 6500 Angstrom, without having to recalibrate the relative sensitivity for the different channels. The rather short plasma pulses of 10-15 ms require a high time resolution. The use of photomultiplier tubes provides a time resolution of 10 mu s which is limited by the transient recorders used. The result is a robust, low-cost system that produces reliable measurements of the radial dependence-of emission from a wide range of impurity ions. (C) 1998 American Institute of Physics. [S0034-6748(98)02606-9].