by or for the United States government is permitted. Diagnostic Neutral Beam and Active Spectroscopy Requirements for the Alcator C-

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 2.5x 1020 m3 will yield, with good signal to noise and ~1cm 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-1 ms time resolution. Motional Stark effect measurements appear feasible over most of the operating density range of the device (at least up to 5x 1020 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 600 viewing angle, 2.5 cm spatial resolution is expected. 1 I