Determination of the D/T fuel mixture using two-photon laser induced fluorescence in combination with neutral beam injection

Abstract

Doppler-free two-photon induced fluorescence in the Lyman-α lines of H, D, and T has been suggested previously as a local and isotope-selective diagnostic of the intrinsic neutral hydrogen densities in magnetically confined fusion plasmas. In the present article, it is shown that the diagnostic potential of this method is significantly increased if it is combined with neutral atom beams whose characteristics are such that efficient production of thermal ground state atoms via charge exchange reactions is achieved. Considerably deeper plasma regions than just the plasma edge can thus be probed and local, isotope-selective information (e.g., the H/D/T density ratios) is obtained on the more relevant ions rather than on the intrinsic neutrals. Additional diagnostic possibilities, e.g., those arising from the spectroscopic investigation of the beam particles themselves, are also discussed.