Resistive MHD Modelling of Quasi-Single Helicity State in the KTX Regimes

TL;DR

This paper uses resistive MHD simulations to explore the formation and characteristics of the quasi-single-helicity state in the KTX device, highlighting the effects of resistivity and plasma beta on the state’s stability and observability.

Contribution

It presents the first detailed resistive MHD modeling of the QSH state in KTX, analyzing how resistivity and plasma parameters influence its formation and duration.

Findings

QSH state forms after transient phase with multiple helicities

Higher beta leads to longer-lasting QSH states

QSH state development linked to dominant linear tearing mode

Abstract

The potential formation of the quasi-single-helicity (QSH) state in the Keda Torus eXperiment (KTX) is investigated in resistive MHD simulations using the NIMROD code. We focus on the effects of finite resistivity on the mode structure and characteristics of the dominant linear and nonlinear resistive tearing-mode in a finite $\beta$, cylindrical configuration of reversed field pinch model for KTX. In the typical resistive regimes of KTX where Lundquist number $S=5 \times 10^4$, the plasma transitions to a steady QSH state after evolving through an initial transient phase with multiple helicities. The dominant mode of the QSH state develops from the dominant linear tearing mode instability. In lower $\beta$ regime, the QSH state are intermittent and short in duration; in higher $\beta$ regime, the QSH state persists for a longer time and should be more observable in experiment.