Neutral helium beam probe

This article discusses the development of a code where diagnostic neutral h elium beam can be used as a probe. The code solves numerically the evolutio n of the population densities of helium atoms at their several different en ergy levels as the beam propagates through the plasma. The collisional radi ative model has been utilized in this numerical calculation. The spatial de pendence of the metastable states of neutral helium atom, as obtained in th is numerical analysis, offers a possible diagnostic tool for tokamak plasma . The spatial evolution for several hypothetical plasma conditions was test ed. Simulation routines were also run with the plasma parameters (density a nd temperature profiles) similar to a shot in the Princeton beta experiment modified (PBX-M) tokamak and a shot in Tokamak Fusion Test Reactor tokamak . A comparison between the simulation result and the experimentally obtaine d data (for each of these two shots) is presented. A good correlation in su ch comparisons for a number of such shots can establish the accurateness an d usefulness of this probe. The result can possibly be extended for other p lasma machines and for various plasma conditions in those machines. (C) 199 9 American Institute of Physics. [S0034-6748(99)01507-5].