Overview of ITER physics deuterium-tritium experiments in JET

An overview of JET experimental results in DT plasmas directly relevant to ITER modes of operation is presented. Experiments in D:T mixtures varying f rom 100:0 to 10:90 and those carried out in hydrogen plasmas show that the H mode threshold power has an approximately inverse isotope mass dependence . Matching some of the key dimensionless parameters: to the ITER values, th e ITER similarity experiments with ITER shape and safety factor q show that the global energy confinement time is practically independent of isotopic mass (similar to A(0.03+/-0.08)), where ii is the atomic mass of the hydrog enic species. Subtracting the edge pedestal energy (which scales as similar to A(0.57+/-0.2)) from the total stored energy leads to a similar to A(-0. 17+/-0.1) dependence of confinement in the plasma core? very similar to tha t expected from the gyro-Bohm transport (similar to A(-0.2)) model. The obs erved scaling of the edge pedestal energy is consistent with a model in whi ch the edge pressure gradient saturates at the ballooning limit over a regi on of width that scales as the ion poloidal Larmor radius governed by the a verage energy of the fast ions in the edge. The steady state total stored e nergy for a given input power in both ICRH and NBI discharges is the same d espite the lower edge pedestal in the ICRH case, which is compensated for b y more peaked power deposition profiles in ICRH. The ELM frequency is small er with NBI; it decreases with isotopic mass in both NBI and ICRH discharge s. A steady state, type I ELMy H mode discharge with ITER shape and q at 3. 8 T/3.8 MA with an input power of 22 MW produced a Q approximate to 0.18 fo r 3.5 s and extrapolates well to ignition with ITER parameters. Here, Q is the ratio of fusion output power to input power. The thermal ELMy H mode co nfinement in both deuterium and tritium gas fuelled plasmas decreases signi ficantly when the plasma density exceeds 0.75 of the Greenwald (n(GW)) limi t, and the maximum density achieved is 0.85n(GW). In L mode, the density li mit decreases with increasing isotope mass roughly in accordance with code predictions. ITER reference ICRH scenarios have been evaluated. Second harm onic heating of tritium at the densities available in JET produces strong t ails and heats electrons predominantly as expected. The He-3 minority in 50 :50 D:T and tritium dominated plasmas showed strong bulk ion heating leadin g to ion temperatures up to 13 keV with ICRH alone. Deuterium minority ion cyclotron heating in tritium plasmas at a pou er level of 0 MW produced ste ady state record values of Q approximate to 0.22 for more than 2.5 s.