Radial profiles of electron temperature and density on the ZT-40M reversed field pinch

A radially resolved Thomson scattering diagnostic has just become operational on ZT-40M. The scattered signal is measured in 10 separate wavelength channels, at ten spatial locations across the plasma cross section. The system consists of a 7 joule, 300 micro-radian laser, and is focussed to a 2 mm waist diameter. The collection system uses double gaussian lenses which focus the laser image onto 10 fiber optic bundles. The fiber bundles are directly connected to a novel spectrometer. The spectrometer operates at f/2 to capture most of the light from the fibers, and achieves excellent ruby rejection by using several reflecting filters. It also images the dispersed light directly onto a photomultiplier tube with 100 anodes, arranged in a 10 by 10 array. Details of the system design are presented. Preliminary profiles of electron temperature and density have been measured on ZT-40M for plasma currents: 120 kA ≤ Irho ≤ 180 kA and densities: ne -- 1-4x1019 m-3 at early times in the discharge. The density profile is typically quite flat to within 2 cm of the plasma edge. The temperature profile is broad but is characterized by an unusual feature in the outer region