Facility for Intense Diagnostic Neutral Beam (IDNB) Development

An intense, pulsed neutral beam source is under development for use as a probe beam on hot, burning plasmas such as in the international thermonuclear experimental reactor (ITER) which is presently in the planning stage. A pulsed, neutral hydrogen beam of 10s of kilo amperes of current can have an alpha particle, charge-exchange- recombination-spectroscopy (alpha-CHERS) signal-to-noise ratio of 100. This beam would allow the measurement, on a single pulse of a few hundred nanoseconds duration, of the local alpha particle distribution function as well as other features of the tokamak plasma such as current density profile, impurity density, and micro-turbulence spectrum. The cross-sections for the CHERS diagnostic dictate operation with proton energies greater than 50keV. A pulsed neutral hydrogen source of this voltage and intensity can be achieved by neutralizing the ion flux from a magnetized ion-diode. The cross-sections for attachment and stripping, when coupled with scaling from Child-Langmiur, space-charge-limited, ion-current flow imply operation below 100keV for maximum neutral fluence. The development of a flashover-anode, ion source for forthcoming evaluation of a neutralizing section is described below. This source operates in the accelerator voltage range 70 to 100keV. Eventually, the flashover-anode, magnetized ion-diode will be replaced with a plasma-anode, magnetized ion-diode. See also ADM002371. Published in 2013 IEEE Pulsed Power Conference, Digest of Technical Papers 1976-2013, and Abstracts. Presented at the 2013 IEEE International Conference on Plasma Science Held in San Francisco, CA on 16-21 June 2013.