Influence of deeply trapped energetic ions on tearing modes

Abstract

The effects of deeply trapped energetic ions (DTEIs) on the stability of tearing modes through stability criterion Δ′ are studied. In contrast to the stabilizing adiabatic effect of background plasma pressure, the adiabatic contribution of the DTEI destabilizes due to the direct coupling between the bad curvature and asymmetrical pressure of energetic ions. When the orbit width is much larger than the island width, the nonadiabatic effect of the DTEI stabilizes, which counteracts the major destabilizing adiabatic contribution. DTEIs are shown to have a net destabilizing effect on the tearing mode. The main physics of destabilization of Δ′ comes from the modification of the Mercier index.

Excitation of 2/1 fishbone-like modes by trapped energetic ions

“…The effect of energetic particles on magnetohydrodynamic (MHD) modes has become an intensive field of research for several years [1][2][3][4][5][6][7]. It was found that sometimes energetic particles (EPs) [8][9][10][11] are capable of improving MHD stability [12] in the plasma [13][14][15][16].…”

Alpha particle ripple loss in CFETR steady-state scenario

“…However, a small perturbation of the magnetic field or electric field can interact with energetic particles and lead to a significant particle loss, which will damage the first wall of tokamak and even lead the plasma to extinguish. In recent years, many pioneering works on energetic particles have been made [10][11][12][13][14][15][16][17][18]. In future reactors, such as ITER and CFETR, the alpha particle heating will act as the primary heating source.…”

Effects of plasma radiation on the nonlinear evolution of neo-classical tearing modes in tokamak plasmas with reversed magnetic shear

“…This explosive burst can lead to a fast driven nonlinear reconnection between both rational surfaces and thus can trigger off-axis sawteeth observed in RMS tokamak plasmas. [51,54] In the early nonlinear phase, the magnetic islands on both rational surfaces continue to grow and drive each other. When the magnetic separatrices of the magnetic islands on both rational surfaces merge together, the field lines of magnetic islands reconnect with the equilibrium field lines.…”

“…[8,32,50] The process is regarded as a new type of secondary instability by the width and the angle rating of triangularization. [51] It is noted that due to the flattening of the pressure profile in the magnetic island, the fraction of the local bootstrap current decreases, triggering the neo-classical double-tearing mode (NDTM) instability in RMS, which is different from the positive magnetic shear. In fact, a preliminary study on NDTM had been conducted by Yu et al and they found that the effects of bootstrap current on the inner rational surface and outer rational surface were quite different.…”