Impurity transport in the pedestal of H-mode plasmas with resonant magnetic perturbations

Abstract

Experiments on DIII-D show that resonant magnetic perturbations (RMPs) reduce the impurity confinement time in the H-mode pedestal below that of naturally ELMy plasmas. STRAHL modeling of discharges with aluminum laser blow off (LBO) injection show increased diffusion in the pedestal of H-mode discharges with RMPs. The increased diffusion from the RMPs provides improved impurity control compared to the naturally ELMy discharges and prevents the buildup of impurities near the edge of the plasma. Tungsten LBO injection into discharges with and without RMPs led to striking differences in the evolution of the discharge. The naturally ELMy discharge became ELM free and showed an increase in edge radiation, leading to the eventual radiative collapse of the plasma. Injecting a similar number of W particles into discharges with RMPs, either with or without ELMs, led to a measurable accumulation of core W but did not significantly impact the evolution of the discharge. These results indicate that RMPs are beneficial for controlling the buildup of impurities in the pedestal region of the plasma.

Non-parametric inference of impurity transport coefficients in the ASDEX Upgrade tokamak

“…The sum of information from various diagnostics provides a more localized likelihood and improves the ill-posed conditions. References [15,16] combined charge exchange spectroscopy (CXRS), vacuum ultraviolet spectroscopy, and soft x-ray measurements and inferred the D and v profiles that are consistent with all the diagnostics.…”

“…Several references [11,[15][16][17] have already reported impurity transport studies by using the Bayesian formalism. In these approaches, the probability distribution for the D and v profiles, which is called the prior, is first defined without considering the data.…”

Monte Carlo Solver for Partly Calculating a Solution to the Poisson Equation in Three-Dimensional Curvilinear Coordinates

“…where Φ (1) and Φ (2) are the numerical solutions calculated twice and the difference is evaluated in the domain D. In the case of Fig. 8, this difference is 1.9 × 10 −2 .…”

“…When numerical simulation methods are used to study impurity transport in the edge region of a quasi-steady tokamak plasma, the three-dimensionality of the magnetic field in the edge region should be considered. Currently, static resonant magnetic perturbations (RMPs) are commonly used to mitigate or suppress edge-localized modes (ELMs) in tokamak plasma [1][2][3]. Victor et al [2] reported that "RMPs are effective at controlling impurity build up in the pedestal region, regardless of ELM suppression."…”

“…Currently, static resonant magnetic perturbations (RMPs) are commonly used to mitigate or suppress edge-localized modes (ELMs) in tokamak plasma [1][2][3]. Victor et al [2] reported that "RMPs are effective at controlling impurity build up in the pedestal region, regardless of ELM suppression." Since the magnetic structure becomes three-dimensional (3D) in the edge region, the electric field generated in the 3D magnetic field is presumed to also affect the impurity transport.…”