The effect of thermo-electric forces on the density profiles in a thermonuclear plasma surrounded by a cold blanket

The behaviour of a thermonuclear multicomponent plasma surrounded by a cold plasma blanket is analysed under reactor-like circumstances. The supply of fuel and the removal of α-particles is effected by diffusion. Instead of taking deuterium and tritium as separate particles, the fuel is simulated by a particle of mass 2.5. The energy of fusion α-particles is supposed to be locally transferred to the plasma and carried off to the wall by heat conduction and radiation. – In the resistive multi-fluid equations describing the problem, the thermo-electric forces arising from electron-ion and ion-ion collisions are included. The analysis is done for a cylindrical plasma column in a strong magnetic field. Toroidal effects are not taken into account and collisional transport is assumed. Discharge parameters, allowing for the existence of a cold blanket, i.e. for which the temperature close to the wall can be kept sufficiently low, are found. It is shown that the α-particle density increases with the radius and that there are cases where the density of a further impurity species has a minimum in the centre of the plasma column. To sustain a steady state it is found that the fuel has to be supplied at the plasma edge with radial velocities of the order of centimetres per second (if we assume on axis a pressure of 20–100 atm, a temperature of ≥ 108 K, a relative α-particle concentration of 0.1–0.7, and a magnetic field strength of 1–20 T).