Re-evaluation of ITER ion cyclotron operating scenarios

Abstract

Various ICRH scenarios for ITER-FEAT are evaluated. A wave propagation and damping study confirms the potential of the second harmonic tritium heating scenario for both heating and current drive purposes. The fundamental deuterium heating scheme is dominated by beryllium and alpha particle absorption. Owing to the reduced ITER size, the low frequency current drive window is lost in practice. A 3He minority greatly enhances the performance. In the early stage of the discharge, the power absorbed by the 3He is transferred to the background ions but, later on, the power of the fast particles (from both the 3He and the tritium tails) is roughly equally distributed between electrons and ions. Using the experimentally established expression for the L to H mode threshold, it is found that the H mode regime can always be reached using RF heating. To achieve Q = 10, high density operation is required. Minority current drive competes with heating and with electron current drive. The scenarios foreseen for the non-activated ITER-FEAT phase are also discussed.

A new ion cyclotron range of frequency scenario for bulk ion heating in deuterium-tritium plasmas: How to utilize intrinsic impurities in our favour

“…For both scenarios, the background X Be = 1% and an optimal D:T=1:1 ratio is assumed. For the 3 He minority scenario, shown in Fig. 2(a), an additional X3 He = 2% is considered.…”

“…As discussed in [1][2][3], preferential bulk ion heating during the ramp-up phase has a number of advantages. These include an improved control over the path to the burn phase and keeping away from the region where the interaction between thermal ions and thermal electrons is weak.…”

“…ICRF scenarios relevant for the D-T plasmas were discussed in detail in Refs. [1,3,4,7], with the emphasis to ITER in, e.g., [8,9]. Many of these scenarios were studied experimentally during the past D-T experiments in JET and TFTR tokamaks [10][11][12][13][14].…”

“…Many of these scenarios were studied experimentally during the past D-T experiments in JET and TFTR tokamaks [10][11][12][13][14]. Currently, the second harmonic heating of tritium ions (ω = 2ω cT ) is considered as the main ICRF scenario for the ITER burn-phase plasmas, and the fundamental heating of a small fraction of 3 He ions (ω = ω c, 3 He ), additionally puffed into the plasma, for the ramp-up low-temperature heating stage of the pulse. In JET, a fourfold increase of the neutron emission was observed when X[ 3 He] = 4% was injected [11].…”

“…However, currently the supply of 3 He reduces and the industrial demand of this gas is progressively increasing [15].…”