Wall stabilization of the rigid ballooning $m=1$ mode in a long-thin mirror trap

TL;DR

This paper investigates how a conducting lateral wall can stabilize the m=1 ballooning mode in a long-thin mirror trap, identifying conditions for effective stabilization and the possibility of full beta range stability.

Contribution

It demonstrates that a conducting wall can stabilize the m=1 mode at high beta values and reveals the existence of two stability zones that can merge for complete stability.

Findings

Effective stabilization requires beta > 70%.

Combining lateral wall with end plates creates two stability zones.

Full beta range stability is achievable under certain conditions.

Abstract

The prospect of stabilization of the $m=1$ ``rigid'' ballooning mode in an open axially symmetric long-thin trap with the help of a conducting lateral wall surrounding a column of isotropic plasma is studied. It is found that for effective wall stabilization, the beta parameter must exceed $70\%$. The dependence of the critical beta on the mirror ratio, the radial pressure profile, and the axial profile of the vacuum magnet has been studied. It is shown that when a conductive lateral wall is combined with conductive end plates simulating attachment of the end MHD stabilizers to the central cell of an open trap, there are two critical beta values and two stability zones that can merge, making stable the entire range of allowable beta values $0<\beta<1$.