Effects of thin wall on resistive wall modes in KTX

Keda Torus eXperiment (KTX) is a newly built reversed field pinch (RFP) device with a copper thin shell. The stability and control of resistive wall modes (RWMs) are essential for the sustained operation of KTX in high parameter regimes. In this work, we investigate the effects of thin wall on the RWM in KTX, based on a cylindrical α-θ model of the RFP equilibrium. We first evaluate the analytical dispersion relation for RWM formulated from the MHD energy principle, and then calculate the dominant linear growth rate of RWM using the full MHD code NIMROD. The dependences of RWM growth rate on the position and the conductivity of vacuum wall for KTX are in qualitative agreement between the two types of calculations. The radial location for the transition from RWM to external kink mode is identified to be 0.53m, same for various wall resistivity conditions, which is well beyond the KTX copper wall location (r=0.4m).