Deuterium depth profiling in JT-60U tiles using the D(3He,p)4He resonant nuclear reaction

Key plasma wall interaction issues towards steady state operation

“…For most devices, the long term retention fraction coming from integrated particle balance (F long $ 10-20%) is larger than what is deduced from post mortem analysis of PFCs [45]. However, both these methods are subject to large error bars 2 : it is difficult to accurately estimate the recovery over long time periods for particle balance on the one hand [46,47], while post mortem analysis is often based on a restricted set of samples, and assumes toroidal/poloidal symmetry to reconstruct the global inventory on the other hand [48][49][50][51]. Extrapolation to ITER with F long = 10%, assuming a gas puff rate of 100 Pam 3 s À1 for 50-50% of D-T, yields an equivalent long term retention of 5 g of T per 400 s shot (which means in reality a higher value after the shot), therefore limiting the number of shots to 70 before reaching the safety limit of 350 g.…”

Particle control in long-pulse H-mode discharges of JT-60U

“…In this situation, the fuel retention is mainly ascribed to the following two processes: (1) the permeation of hydrogen deep into the wall and (2) the co-deposition of hydrogen with impurities such as carbon. The retention rate due to permeation reduces with the ion fluence [1,2], and the fuel retention by the co-deposition works in both short-and long-pulse discharges. Hence, by the decrease in the surface absorption rate and the permeation rate, the controllability of the plasma density is assumed to be lower in a long-pulse discharge than in a short-pulse discharge.…”

Tritium absorption of co-deposited carbon films

“…Because of its high thermal shock resistivity and high thermal conductivity, carbon material is a candidate as a divertor target in ITER. Carbon materials are easily eroded by incident hydrogen bombardment and the sputtered carbon atoms are co-deposited with hydrogen isotopes on the walls nearby the divertor target [2][3][4][5][6]. Hydrogen isotopes retention in carbon films retained by co-deposition and implantation processes have been well investigated so far [7,8].…”