Diagnostic neutral beam and active spectroscopy requirements for the Alcator C-Mod tokamak (invited)

Considerations are presented on the application of a diagnostic neutral beam to the Alcator C-Mod tokamak for active profile measurements of ion temperature, poloidal and toroidal rotation, impurity and minority species densities, and internal magnetic field. Calculations indicate that, for a typical 50 keV, 0.13 MW hydrogen beam, charge exchange recombination measurements for plasmas with line average densities up to 2.5x10(20) m(-3) will yield, with good signal-to-noise ratio and similar to 1 cm spatial resolution, measurements of helium and low Z impurity density profiles with better than 1 ms time resolution, and ion temperature 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 measurements will depend on the toroidal width of the beam and the angle of the view with respect to the beam; for a 5 cm wide beam with a 60 degrees viewing angle, 2.5 cm spatial resolution is expected. (C) 1997 American Institute of Physics.