Plasma isotopic change over experiments in JET under Carbon and ITER-Like Wall conditions

Starting with a wall loaded by H₂, change over experiments from H₂ to D₂ have been carried out in JET-ILW. A series of 13 repetitive pulses (cumulating 215 s in divertor configuration) have been performed under conditions of: I_p = 2.0 MA, B_T = 2.4 T, 〈n_e〉 = 4.5 × 10¹⁹ m⁻³ with a constant gas injection of 3.0 × 10²¹ D s⁻¹ and 0.5 MW of auxiliary heating by ICRH in L-mode. Gas balance analysis shows that the total amount of H removed from the wall is in the range of 3 × 10²² D compared to 2 × 10²³ D for JET-C. This is consistent with the faster decay of the H plasma concentration and the drop of the retention also by a similar factor when removing all the carbon components. Isotopic plasma wall changeover is also demonstrated to allow for removal of some D/T from the device. However, since plasma change over also contributes to long-term retention by codeposition, in ITER, change over in between each discharge might not be effective to reduce the fuel retention on the long-term