Conceptual design of beam-ion profile diagnostics for the DIII-D tokamak

Three diagnostic concepts that measure the radial profile of deuterium beam ions are assessed. One diagnostic exploits 3 MeV protons that are lost on their first orbit. Since beam-plasma. reactions usually predominate in the discharges of interest, the beam-ion density profile can be inferred from the d-d fusion reaction profile. The relatively modest plasma current (similar to 1.6 MA) implies that a significant fraction of the charged d-d fusion reaction products are unconfined. The second diagnostic employs a neutron collimator. For this diagnostic, neutron scattering is a major concern. Both fusion product diagnostics are sensitive to uncertainties in the thermonuclear rate, so the anomalous beam-ion transport must exceed D(B)greater than or similar to1.0 m(2)/s to be detectable. The third diagnostic employs an array of natural diamond detectors that is configured to measure the signal from beam ions that charge exchange with neutrals in a modulated heating beam. The sensitivity to uncertainties caused by pitch-angle scattering of the beam ions can be minimized by a prudent choice of detection angle. Because of attenuation of the escaping neutrals the effective resolution is D(B)similar to0.5 m(2)/s. (C) 2003 American Institute of Physics.