Counterstreaming-ion tokamak neutron source for large-area surface radiation studies

A tokamak neutron source that produces a neutron flux approximately 1013 n/cm2/s over a wall test-area of 30 m2 is designed using near state-of-the-art tokamak and neutral-beam injection technologies. To maximize fusion reactivity, D and T plasma ions are grouped in two distinct quasi-thermal velocity distributions, oppositely displaced in velocity along the magnetic axis. Such counterstreaming distributions can be set up by tangential injection of all plasma ions by oppositely directed D and T neutral beams, by facilitating removal of completely decelerated ions, and by minimizing plasma recycling. Fusion energy is produced principally by head-on collisions between D and T ions in the counterstreaming distributions. For injection energies of 40-60 keV, and typical tokamak parameters, the fusion power density can be approximately 1 W/cm3, with Q approximately 1 attainable for T/sub e/ = 3.4 keV and electron energy confinement parameter n/sub e/tau/sub E/ approximately 2 x 1012 cm-3 s. All plasma fueling is carried out by the injected beams, and when a significant fraction of the electron population is trapped, the plasma current can be maintained by the beams