3-Dimensional density profiles in edge plasma simulations for ICRF heating

Abstract

Abstract. In this paper we discuss improvements made to two codes for the simulation of ICRF waves in edge plasmas: SSWICH-SW, which self-consistently models the interplay between sheath physics and radiofrequency waves (the slow wave), and RAPLICASOL, a Finite Element solver for Maxwell's equations in the cold plasma approximation. We have extended both to be able to handle 3D plasma density profiles. A comparison between a 1D and a 3D simulation reveals that the density profile dimensionality has a relatively small effect on E at the aperture, but a large effect on the sheath potential at the antenna limiters

Characterization of 3-strap antennas in ASDEX Upgrade

“…Better quantitative agreement between simulations and measurements is presenting a challenging task, given the uncertainties and variations in the experimental input [2,6]. An independent method to reduce the RF currents by actively feeding the antenna limiters and synchronizing operation of all four antennas in ASDEX Upgrade could be tested in the future.…”

“…As can be inferred from [6], details of 3D density profile have a significant effect on the RF image currents and E || at the limiters. On top of that, the profiles are not stationary in experiments [2].…”

“…Horizontal stripes on V RF are visible in Fig.2 and Fig.3 and can be explained by evolving conditions during scans of P central /P outer conducted at fixed as well as by associated non-linearities. The 3D density profile in front of the antenna is likely evolving and affecting the overall balance of RF image currents at the antenna [2], as shown by calculations in [6]. Measurements of DC current I DC have not been reported before for the 3-strap antennas and require a particular attention.…”

Recent progress on improving ICRF coupling and reducing RF-specific impurities in ASDEX Upgrade

“…Theoretical approaches [24][25][26] to model sheaths are being developed and will be validated against measurements on ASDEX Upgrade [11,27] and on IShTAR [28,29]. Theoretical insight of experimental results will provide key guidelines to design antennas with reduced sheaths and RF-induced impurities.…”

Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments

“…RAPLICASOL was not originally intended to be a standalone RF code, but rather to be the RF module of the nonlinear sheath code SSWICH [10,11]. As we extended the capabilites of both RAPLICASOL and SSWICH, it became apparent that RAPLICASOL has its own uses independent from SSWICH, such as the calculation of coupling resistances when the plasma is not toroidally and poloidally uniform [8,12].…”