Enhanced particle transport caused by resonant magnetic perturbations in the J-TEXT tokamak

Abstract

The effect of resonant magnetic perturbations (RMPs) on particle transport has been studied in J-TEXT tokamak. It is found that for the discharges with an existing saturated 2/1 resistive tearing mode, applied RMPs of moderate amplitude lead to a decrease in electron density with a relative amplitude 3% < |ne/ne0| < 10% in plasma core, and the mode stabilization and electron temperature increase are observed simultaneously in this case. Sufficiently large amplitude of RMPs, however, lead to locked modes and much larger decrease in the electron density as well as in the electron temperature, with |ne/ne0| ~ 20%. For the discharges without 2/1 tearing modes, applied RMPs cause a relative density decrease |ne/ne0| ~ 10% (30%) before (after) field penetration. Using the two-fluid equations and experimental parameters as input, the numerical results approximately agree with experimental observations.

Density modulation experiment to determine transport coefficients on Joint-TEXT Tokamak

“…For the case of I p = 130 kA, B t = 2.0 T, variation of τ p follows a similar pattern. In addition, the τ p inferred by the density modulation experiment is in good agreement with the result given by Qiming Hu, 18 where the transport coefficients are obtained by fitting measured density with sinusoidal functions. 19 It gives τ p ∼ 26 ms at n 0 ∼ 1.5×10 19 m −3 , but does not consider the particle source term.…”

Plasma response to m/n = 3/1 resonant magnetic perturbation at J-TEXT Tokamak

“…Previous studies on J-TEXT exhibit resonant feature for the influence of RMPs on particle transport, and density pump-out occurs when m/n = 2/1 locked mode is triggered by the 2/1 RMP [32], where m and n are the poloidal and toroidal mode number, respectively. Recent studies by using rotating 2/1 RMPs showed that RMPs improve (degrade) particle confinement when its frequency is higher (lower) than the natural 2/1 tearing mode (TM) frequency, and the amount of change in electron density is proportional to the difference between these two frequencies [33], being in good agreement with numerical predictions [27,28].…”

Influence of rotating resonant magnetic perturbations on particle confinement

“…In previous J-TEXT experiments using static RMPs, the edge safety factor qa was varied from 2.7 to 3.8, and RMPs were varied from a spectrum dominated by the 2/1 component to others with negligible 2/1 component. Significant change in the electron density is observed only when there was a large resonant 2/1 component RMP to cause mode locking or mode penetration [22]. The required static RMP amplitude at r = a to cause mode locking is about the same as that of rotating RMPs if the value of ∆f is about the same [22].…”

“…Significant change in the electron density is observed only when there was a large resonant 2/1 component RMP to cause mode locking or mode penetration [22]. The required static RMP amplitude at r = a to cause mode locking is about the same as that of rotating RMPs if the value of ∆f is about the same [22].…”

“…The improved particle confinement was achieved on TEXTOR when static RMPs is applied to the plasmas with neutral beam injection in the plasma current direction [20]. In J-TEXT Ohmic discharges in which m/n = 2/1 modes rotate in the counter-current direction, degraded particle confinement is usually observed after applying static RMPs dominated by the 2/1 component [22], where m and n are the poloidal and toroidal mode number.…”