• Book : 178()
• Pub. Date : 2025
• Page : pp.105492
• Keyword :

• Book : 604()
• Pub. Date : 2025
• Page : pp.155535
• Keyword :

• Book : 227()
• Pub. Date : 2025
• Page : pp.112400
• Keyword :

• Book : 178()
• Pub. Date : 2025
• Page : pp.105519
• Keyword :

• Book : 431()
• Pub. Date : 2025
• Page : pp.113720
• Keyword :

Abstract

The velocity-space distribution of the fast-ion loss in EAST neutral-beam injection (NBI) heating discharge is obtained both from Scintillator-based fast-ion loss detector (FILD) signals and by ASCOT5 and FILDSIM simulations. The results of simulations are in good agreement with the distribution of beam-ion losses measured with FILD of EAST and the correctness of the fast-ion loss distribution has been demonstrated. Simulations indicate that the beam-ion losses observed by the FILD probe are attributed to the fast ions from both the high-field side (HFS) and the low-field side (LFS). However, the beam-ion losses from the HFS (associated with NBI1L) have not been observed experimentally due to the limited detecting range of the FILD probe. Therefore, an upgrade and modification of the FILD probe was carried out in 2022 to enable the detection of fast-ion loss with smaller pitch angles. Comparative analysis is conducted in neutral-beam injection (NBI2R) discharges after the upgrade, which indicates that the velocity-space distribution of beam-ion losses from the HFS has strong agreement between experimental measurements and simulation results. However, the experimental and simulated results of the velocity-space distribution of beam-ion losses from the LFS shows inconsistencies, primarily because the BBNBI module in the simulation does not consider the contributions of boundary neutral particles to neutral-beam deposition (ionization reactions). These conclusions not only provide valuable references for improving the neutral-beam deposition model but also establish a fundamental basis for further exploring the mechanisms of fast-ion loss under various conditions on the EAST tokamak.

• Book : 65(1)
• Pub. Date : 2025
• Page : pp.016026
• Keyword :

Abstract

Thanks to the tail of fast electrons generated by the lower hybrid (LH) waves, the plasma conductivity changes significantly with respect to the ohmic heating status (Fisch 1985 Phys. Fluids28 245). In this paper, the synergy effects of lower hybrid current drive (LHCD) in the presence of a DC electric field (namely, the loop voltage Vloop ≠ 0) on the EAST tokamak are studied numerically using the ray tracing and Fokker-Planck tools of C3PO/LUKE. In addition to the normal case of a positive loop voltage with an asymmetric power spectrum (namely, co-current LHCD), the synergy effects of negative loop voltage with an asymmetric power spectrum (namely, counter LHCD), and positive/negative loop voltage with a symmetric power spectrum are also investigated, which are previously rarely reported. It is found that the total plasma conductivity can be increased by a factor of 1.68-2.18 (depending on the value of Vloop) when a 1.1 MW LH power at 2.45 GHz with a symmetric power spectrum is injected. Furthermore, unlike the asymmetric power spectrum, the direction of the sum of the pure LH current (Ilh0) and the synergetic current (Iad) resulting from the variation in plasma conductivity is always in line with the ohmic current (Ioh) for a symmetric power spectrum, which is favorable for AC tokamak operation. These simulated results are helpful for LHCD applications, especially in current ramp-up and AC operation.

• Book : 65(1)
• Pub. Date : 2025
• Page : pp.016016
• Keyword :

• Book : 604()
• Pub. Date : 2025
• Page : pp.155470
• Keyword :

• Book : 217()
• Pub. Date : 2025
• Page : pp.29-46
• Keyword :

• Book : 178()
• Pub. Date : 2025
• Page : pp.105520
• Keyword :