Verification of the Equilibrium and MHD Stability Codes within the Integrated Tokamak Modeling Task Force

Validation of the numerical tools used for modeling of the fusion plasma is an important step in the interpretation of experimental results. As several codes are usually used in the fusion community to model the same plasma processes, prior verification of the codes should be done in order to avoid discrepancies in the results treatment. Often numerical codes use different post- and pre-processing routines, coordinate system conventions, etc. These make such comparison complicated. One of the main efforts within the Integrated Tokamak Modeling Task Force (ITM TF) is the verification and validation of the existing numerical tools on the existing tokamak experiments. The framework developed in ITM provides common standard interfaces for accessing, storing and exchanging data. All codes integrated in the ITM framework use this common interface which makes the verification process straightforward. Analysis of the plasma equilibrium and MHD stability is one of the topics covered by the ITM. Several equilibrium and MHD stability codes presently integrated in the ITM framework are verified in this work including fixed boundary equilibrium codes CHEASE, HELENA, SPIDER, CAXE and linear MHD stability codes MARS, MARS-F and KINX. Reconstruction of the equilibrium for the JET the Pulse No: 74221 using EQUAL or EFIT codes is used as starting point of these studies. The steady state experimental scenario was studied in the chosen pulse with high values of normalized beta observed (bN up to 2.4). The pulse was terminated by a disruption at t 9.24 sec due to a loss of vertical control. The studied operational scenario with such high values of bN could be unstable to the ideal kink modes allowing verification of both equilibrium and linear stability codes using one set of experimental conditions.
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