Suppression of large edge localized modes in high confinement DIII-D plasmas with a stochastic magnetic boundary

Abstract

Large 70 Hz Type-I edge localized modes (ELMs) are converted into small 130 Hz oscillations using edge resonant magnetic perturbations (RMPs) from a coil with currents 60.4% I p in double null DIII-D plasmas. When the RMP is properly phased with respect to the background field errors, all but a few isolated ELM-like events are suppressed. The impulsive pedestal energy loss DE ELM /Dt 1/2 to the scrape-of layer is reduced a factor of P20 relative to the Type-I ELMs and the core confinement is unaffected by the perturbation field. Significant changes in the properties of the ELMs are also observed when edge RMPs are applied to lower single null plasmas but the nature of these changes are much more complex. Both lower single null and double null plasmas are being studied to determine how ELM control techniques based on the application of edge RMPs can be expected to scale to future devices such as ITER.

Analysis of edge magnetic field line structure in ITER due to in-vessel ELM control coils

“…Resonant magnetic perturbations (RMPs) have proven to be successful for the suppression and mitigation of edge localized modes [1,2] (ELMs) in DIII-D [3,4], JET [5] and ASDEX-U [6]. ELMs drive impulsive energy losses and can be detrimental to plasma facing surfaces in future ITER high power experiments.…”

A Comparative Study of Electron Heat Transport in a Stochastic and a Non‐Stochastic Magnetic Field

“…[1][2][3]13] Also, stochastic fields were used at the plasma edge in some tokamak experiments to achieve a more evenly distributed energy loadings on the walls and possibly to suppress edge localized modes. [14,15] The experimental studies obtained a qualitative control over the Edge Localized Mode (ELM) by imposing Resonant Magnetic Perturbations (RMPs) at the plasma edge as the recent experiments carried out on DIII-D, JET and TEXTOR [7][8][9].…”

Real-time wavelet detection of crashes in limit cycles of non-stationary fusion plasmas

“…This scaling function (t) is not a wavelet because +∞ −∞ (t)dt = 1, see (2). The scaling function (father wavelet) transform and (mother) wavelet transform are defined as [40]:…”

“…This is done by means of a maxima chain (Section 3.3) whereby a number of maxima, which indicate the middle of the edge, are followed from the maxima in a scale m > 1 to lower scales preferably to m = 1. The maxima are detected in every scale by a simple maxima detector (d[1] < d max [2] > d [3]) and are stored in a buffer, which has the size of the wavelet with the biggest dilation. Otherwise, due to the different delays for the different scales, important maxima can be lost.…”

“…This scenario features a periodic reorganization of the pressure and magnetic flux in both the plasma core (often referred to as the sawtooth instability) and the plasma edge (referred to as the Edge Localized Mode or ELM) [2]. The sawtooth affects the exhaust of the fusion ash (helium), the replenishing of the fusion fuels deuterium and tritium, drives premature losses of energetic particles required for plasma self-heating and triggers performance limiting, secondary instabilities, referred to as Neoclassical Tearing Modes (NTMs).…”