Prospects for charge-exchange-recombination-based measurements on International Thermonuclear Experimental Reactor using a helium diagnostic neutral beam
Dm. Thomas et al., Prospects for charge-exchange-recombination-based measurements on International Thermonuclear Experimental Reactor using a helium diagnostic neutral beam, REV SCI INS, 70(1), 1999, pp. 886-889
Several important measurements in the International Thermonuclear Experimen
tal Reactor (ITER) diagnostic mission, including the primary one of core he
lium ash density, are expected to be addressed using active spectroscopic t
echniques. These methods rely on the use of a dedicated diagnostic neutral
beam (DNB) which has been optimized for the dual requirements of beam penet
ration and charge exchange cross section. For hydrogenic beams, this result
s in an optimal beam energy of similar to 100 keV/amu. Signal-to-noise esti
mates using realistic geometries and the existing ITER profile and equilibr
ium data have confirmed the stringent requirements on beam quality and inte
nsity to satisfy the stated ITER measurement precisions. In this article we
consider the use of a neutral helium DNB for making active spectroscopic m
easurements on ITER, since helium beams offer better penetration in dense p
lasma for a given energy, and the prospects for given source performance ma
y also be improved. Drawbacks include the more difficult absolute calibrati
on of the beam density profile as well as the fundamental problem of unique
ly identifying the source (fusion-based ash, beam core fuelling, or edge DN
B neutralizer/source efflux) of the observed He charge-exchange recombinati
on line in order to unambiguously characterize core helium buildup and conf
inement on ITER. (C) 1999 American Institute of Physics. [S0034-6748(99)650
01-8].