A novel method for tritium transport studies and its validation at JET

A new method combining a free-form solution for the neutron emissivity and ratio method [16] is applied to the investigation of tritium transport in JET plasmas. The minimum fisher regularization (MFR) method [14, 15] which is being developed and studied alongside a range of other methods at JET, was used to obtain the neutron emissivity. The tritium concentration or fuel ion density ratio n_T/n_D in the core plasma was derived from both 2.45 MeV D-D neutron profiles and 14.07 MeV D-T neutron profiles using the ratio method. By using a new anisotropic smoothing constraint in the MFR method 2D neutron emisivity profiles were significantly improved as compared to first results obtained with this method. 1-D profiles of tritium concentration suitable for transport analysis were then obtained by subsequent poloidal integration (fig.2). The tritium transport was studied for a set of discharges with trace tritium puffs selected from the JET trace tritium experiments [4, 5, 6]. Local tritium transport coefficients were derived from the particle flux equation Γ = -D∇n_T + Vn_T, where D is the particle diffusivity and V the convection velocity. First results for the transport coefficients are presented and discussed. Preliminary comparisons show that the obtained core tritium diffusivity values are comparable to neoclassical ones at high collisionalities and decrease with increasing collisionality.