Spatially resolved toroidal plasma rotation with ICRF on JET

Abstract

Plasmas heated by ICRF only in the JET tokamak show distinct structures in the toroidal rotation profile, with regions where dω/dr>0 when the minority cyclotron resonance layer is far off-axis. The rotation is dominantly co-current with a clear off-axis maximum. There is only a slight difference between a high-field side (HFS) or a low-field side position of this resonance layer: the off-axis maximum in the rotation profile is modestly higher for the HFS position. This is in contrast to the predictions of theories that rely mainly on the effects arising from ICRF-driven fast ions to account for ICRF-induced plasma rotation. The differences due to the direction of the antenna spectrum (co- or counter-) are small. A more central deposition of the ICRF power in L-mode and operation in H-mode both lead to more centrally peaked profiles, both in the co-direction. Strong MHD modes brake the rotation and lead to overall flat rotation profiles.

Toroidal rotation and momentum transport in Alcator C-Mod plasmas with no momentum input

“…Despite the fact that there is no momentum input in Alcator C-Mod plasmas, ICRF [16,17] and Ohmic [16,18,19] H-mode discharges are found to have substantial spontaneous co-current toroidal impurity rotation. Similar observations have been made on other devices such as JET [20,21], COMPASS [22] and Tore Supra [23][24][25]. The Alcator C-Mod rotation results are summarized in the following.…”

Dimensionless size scaling of intrinsic rotation in DIII-D

“…Published data from JET [9] and C-Mod [4] also fit this scaling. In machine parameters, this scaling is related to the ion temperature dominant scaling postulated by Parra et al on physical grounds [10], where T i is the ion temperature.…”

“…In addition to DIII-D data, we have included data from JET and C-Mod discharges that have been the subject of prior publication [4,9]. In JET, the L-Mode discharges had relatively low power ICRF heating and the velocity profiles are qualitatively similar to the ECH DIII-D discharges, so we used the same methodology in adding these data.…”

“…The C-Mod data are from four discharges described in Table 1 of reference [4]. The JET data are from the low ICRF power phase of discharges presented in reference [9]. The black crosses in the JET points are from the first CER time slice in the NBI blips utilized there.…”

“…For JET we use data from one of the first intrinsic rotation experiments done on JET, with results published in [9]. In JET short NBI pulses are used for CER velocity measurements of C 6+ , as in DIII-D. All NBI is in the co-I p direction for these discharges.…”