TRANSPORT OF DEUTERIUM, TRITIUM AND HELIUM IN A TOKAMAK
A one-dimensional numerical model for determining steady state radial profiles of the densities of the particles, including neutrals, in a multi-species toroidal plasma is described. For prescribed temperature profiles, the coupled momentum and particle balances of the ions are solved numerically with a newly developed compact finite difference scheme for a non-equidistant mesh. Neutral densities are obtained by solving the Boltzmann equations, using a collocation method. The model is applied to deuterium - tritium plasmas without and with a helium admixture. For the charged particles, Pfirsch-Schlueter transport, including the highly collisional extension, and either of two anomalous transport models are adopted. For equal densities of deuterons and tritons in the plasma centre, the neutral tritium density in front of the wall is found to be 1.3 to 1.6 times higher than that of deuterium, depending on the plasma density, the temperature profile and the transport model. Secondly, it is found that pumping neutral helium, originating from fusion alpha particles, out of a cold plasma gas density, corresponding to a relative abundance of aplpha particles in the plasma core below 10 %, is very low. Although depending strongly on the ion transport model and being increased by elastic collisions between neutral helium and charged hydrogen isotopes, the neutral helium enrichment ratio is always much less than unity.
Bibliographic Reference: WRITE TO FOM-INSTITUUT VOOR PLASMAFYSICA RIJNHUIZEN, P.O. BOX 7, 3430-AA-NIEUWEGEIN (THE NETHERLANDS), MENTIONING RIJNHUIZEN REPORT 84-150, 1984
Record Number: 1989122098300 / Last updated on: 1987-01-01
Available languages: en