Requirements for an active spectroscopy diagnostic with neutral beams on the RFX reversed field pinch

The conceptual feasibility of an active spectroscopic diagnostic on reverse d field experiment (RFX) to measure the radial profiles of ion temperature, toroidal and poloidal drift velocities, and main impurity densities is exa mined. In particular a charge exchange recombination spectroscopy experimen t is simulated for carbon and helium impurities. The motional Stark effect on the beam atoms injected into RFX is estimated as a means to measure the magnetic field pitch and intensity. A modulated beam injector (500 Hz) with 2 A of equivalent current and an energy of 50 keV/amu appears to be adequa te to perform the measurements over a reasonable range of operational regim es. (C) 1999 American Institute of Physics. [S0034-6748(99)70601-5].