The effect of resonant magnetic perturbation with different poloidal mode numbers on peeling-ballooning modes

The effect of resonant magnetic perturbation(RMP)with different poloidal mode numbers on peeling-ballooning(P-B)modes is simulated with the BOUT++code.In order to investigate the physical mechanism of edge-localized mode mitigated by RMP,a series of RMPs with different poloidal mode numbers are applied into the four-field P-B mode simulation module separately.The results indicate that RMP has a better reducing effect on the energy loss from the pedestal when the resonant position is near the bottom and top of pedestal rather than near the middle.The RMP could influence P-B modes through the following effects:on the one hand,the E×B shearing rate is significantly stronger when the RMP(resonant surface locates at the top of the pedestal)is added,which can suppress the radial propagation of the negative pressure perturbation and reduce energy loss from the pedestal.On the other hand,the coupling of toroidal modes in the nonlinear phase is enhanced when RMPs are added,which motivated the growth of multiple toroidal modes,and the turbulence fluctuation level is weaker with the RMP when the resonant surface is located at the bottom of the pedestal.

Influence of Poloidal Rotation of Plasma on Peeling-Ballooning Modes

Influence of the poloidal rotation of the plasma on Peeling-Ballooning modes(P-B modes)is studied with BOUT++code.The results show that the poloidal rotation destabilizes P-B modes because of the effect of Kelvin-Helmholtz instability when the poloidal rotation is large enough and the shear is small,and the shear of the poloidal rotation can stabilize high-n P-B modes when the shear is increased.

Mitigation of ELMs by Electrostatic Field in Tokamaks

Mitigation of ELMs by electrostatic field is studied. The perpendicular heating in cyclotron waves tends to pile up the resonant particles toward the low magnetic field side in which a electrostatic field may result [J. Y. Hsu, V. S. Chan, R. W. Harvey, R. Prater, and S. K. Wong, Phys. Rev. Lett. 53, 564 (1984)]. The electrostatic field can make circulating particles trapped or make trapped particles circulating depending on the field direction. The trapped- particle population and bootstrap current change accordantly. Modulating bootstrap current, mitigation of type-1 ELM by the electrostatic field is possible. The electrostatic potential needed for the mitigation is quantitatively estimated. Experiments by either ECRH or biasing are being prepared to verify the theory.

On the Jebsen-Birkhoff Theorem in a Born-Infeld Type Theory of Gravity

In this paper we work with a special theory of gravity|the Novello-Di Lorenci-Luciane (hereby called NDL theory) which extends the Feynman-Deser standard theoretical-fi eld approach to General Relativity. In the so-called NDL theory, matter interacts universally with gravity in accordance with the Weak Equivalence Principle, while gravitons have a nonlinear self-interaction. Our main aim in this work is to show that, though the NDL theory does not admit a Schwarzschild solution, the Jebsen-Birkhoff theorem is still valid in this framework.