DIAGNOSTIC NEUTRAL BEAM AND ACTIVE SPECTROSCOPY REQUIREMENTS FOR THE ALCATOR C-MOD TOKAMAK (INVITED)

Considerations are presented on the application of a diagnostic neutra l beam to the Alcator C-Mod tokamak for active profile measurements of ion temperature, poloidal and toroidal rotation, impurity and minorit y species densities, and internal magnetic field. Calculations indicat e that, for a typical 50 keV, 0.13 MW hydrogen beam, charge exchange r ecombination measurements for plasmas with line average densities up t o 2.5x10(20) m(-3) will yield, with good signal-to-noise ratio and sim ilar to 1 cm spatial resolution, measurements of helium and low Z impu rity density profiles with better than 1 ms time resolution, and ion t emperature and rotation profiles with similar to 1 ms time resolution. Motional Stark effect (MSE) measurements appear feasible over most of the operating density range of the device (at least up to 5x10(20) m( -3)), also with ms time resolution. Spatial resolution of the MSE meas urements will depend on the toroidal width of the beam and the angle o f the view with respect to the beam; for a 5 cm wide beam with a 60 de grees viewing angle, 2.5 cm spatial resolution is expected. (C) 1997 A merican Institute of Physics.