Multipoint Thomson scattering system for the extrap Z-pinch experiment

A Thomson scattering system for simultaneous measurements of the electron temperature and density at three different positions and at two different times during a single plasma shot has been developed for a Z-pinch experiment. The plasma in the pinch is characterized by densities in the range from 5 × 10²⁰ to 10²² m⁻³, temperatures up to 30 eV and a pinch radius of the order of 1 cm. The spatial resolution of three points with 3 mm between points is obtained by imaging the plasma onto a matrix of quartz optical fibres at the output slit of the spectrometer. Thus only one spectrometer is used together with 15 PM-tubes to detect the scattered radiation as well as the background radiation. Due to the relatively dense plasma prevailing in this Z-pinch discharge the number of scattered photons is large and the photon to electron conversion noise is small. Therefore the background radiation is the most important factor limiting the accuracy of the measurements.