Burn-up of fusion-produced tritons and3He ions in PLT and PDX

The d(d,p)t and d(d,n) 3 He fusion reactions produce 1 MeV tritons and 0.8 MeV 3 He ions which can subsequently undergo d(t, n) a and d( 3 He,p) a fusion reactions.The magnitude of this triton and 3He ion 'burn-up' was measured on the PLT and PDX tokamaks by detection of the 14 MeV neutron and 15 MeV proton emission.In discharges with B,j>> 2 T, the measured ^e and triton burn-up is consistent (within a factor of three) with predictions based on classical theories of ion confinement and slowing down.In discharges with weaker toroidal fields but constant plasma current, the burn-up of both ions fell by more than a factor of ten so that the observed burn-up was significantly less than expected classically.The rate of energy loss is computed using the Coulomb drag experienced by the MeV ion at its birth position rather than the drag along its actual orbit.