Localized bulk electron heating with ICRF mode conversion in the JET tokamak

Abstract

Ion cyclotron resonance frequencies (ICRF) mode conversion has been developed for localized on-axis and off-axis bulk electron heating on the JET tokamak. The fast magnetosonic waves launched from the low-field side ICRF antennas are mode-converted to short-wavelength waves on the high-field side of the 3 He ion cyclotron resonance layer in D and 4 He plasmas and subsequently damped on the bulk electrons. The resulting electron power deposition, measured using ICRF power modulation, is narrow with a typical full-width at half-maximum of ≈30 cm (i.e. about 30% of the minor radius) and the total deposited power to electrons comprises at least up to 80% of the applied ICRF power. The ICRF mode conversion power deposition has been kept constant using 3 He bleed throughout the ICRF phase with a typical duration of 4-6 s, i.e. 15-40 energy confinement times. Using waves propagating in the counter-current direction minimizes competing ion damping in the presence of co-injected deuterium beam ions.

Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating

“…Since (Z/A) T < (Z/A) 9Be < (Z/A) D , 9 Be ions can efficiently absorb RF power and transfer most of their energy to D and T ions during their collisional slowing-down, a feature particularly attractive for a fusion reactor 10 . As another example of three-ion technique, we mention the observed parasitic off-axis absorption of ICRH power by 7 Li impurities in TFTR D-T plasmas 27 . Low-temperature plasmas offer an even larger variety of scenarios since light ion species are not necessarily fully ionized.…”

“…Low-temperature plasmas offer an even larger variety of scenarios since light ion species are not necessarily fully ionized. Ion species T 9 Be, 7 Li, 22 Ne D, 4 He, 12 31 . Their study resembles closely the ( 3 He)-H minority heating in tokamaks.…”

“…Instead, such plasmas are typically used for localized electron heating through mode conversion (see ref. 7 for more details).…”

An unconditionally stable time-domain discretization on cartesian meshes for the simulation of nonuniform magnetized cold plasma

“…A third example involves mode conversion from the fast wave to the ioncyclotron wave, a phenomenon of interest for Ion-Cyclotron Resonance Heating (ICRH) [9,10]. This example is similar to the one used by Smithe [7].…”

“…Explicit solutions have been proposed [7] and are stable provided the vacuum Courant condition is obeyed. This is problematic when simulating phenomena whose wavelength is much shorter than the vacuum wavelength λ vac = 2πc/ω, like the waves that occur in mode conversion layers [7,8,9,10]. In that case, to resolve the phenomena in space (i.e.…”