TY - JOUR

T1 - On the stability of the m = 1 rigid ballooning mode in a mirror trap with high-beta sloshing ions

AU - Kotelnikov, Igor a.

N1 - This work was supported by the Russian Science Foundation under the Grant 24-12-00309 awarded to Novosibirsk State University. This work is also a part of the state assignment of the Russian Federation for the Budker Institute of Nuclear Physics.

PY - 2025/4/14

Y1 - 2025/4/14

N2 - Stability of the ‘rigid’ ( m=1 ) ballooning mode in a mirror axisymmetric trap is studied for the case of oblique neutral beam injection (NBI), which creates an anisotropic population of fast sloshing ions. Since small-scale modes with azimuthal numbers m>1 in long thin (paraxial) mirror traps are easily stabilized by finite-Larmor-radius (FLR) effects, suppression of the rigid ballooning and flute modes would mean stabilization of all magnetohydrodynamic (MHD) modes, with the exception of the mirror and firehose disturbances, which are intensively studied in geophysics, but have not yet been identified in mirror traps. Large-scale ballooning mode can, in principle, be suppressed either by the lateral perfectly conducting wall, or by the end MHD anchors such as the cusp, by biased limiters or by a combination of these two methods. The effects of the wall shape, vacuum gap width between the plasma column and the lateral wall, angle of oblique NBI, radial profile of the plasma pressure and axial profile of the vacuum magnetic field are studied. It is confirmed that the lateral conducting wall still creates the upper stability zone, where the ratio β of the plasma pressure to the pressure of vacuum magnetic field exceeds the second critical value βcr2, β>βcr2. However, in many cases the upper zone is clamped from above by mirror instability. When the lateral wall is combined with end MHD anchors, a lower stability zone β

AB - Stability of the ‘rigid’ ( m=1 ) ballooning mode in a mirror axisymmetric trap is studied for the case of oblique neutral beam injection (NBI), which creates an anisotropic population of fast sloshing ions. Since small-scale modes with azimuthal numbers m>1 in long thin (paraxial) mirror traps are easily stabilized by finite-Larmor-radius (FLR) effects, suppression of the rigid ballooning and flute modes would mean stabilization of all magnetohydrodynamic (MHD) modes, with the exception of the mirror and firehose disturbances, which are intensively studied in geophysics, but have not yet been identified in mirror traps. Large-scale ballooning mode can, in principle, be suppressed either by the lateral perfectly conducting wall, or by the end MHD anchors such as the cusp, by biased limiters or by a combination of these two methods. The effects of the wall shape, vacuum gap width between the plasma column and the lateral wall, angle of oblique NBI, radial profile of the plasma pressure and axial profile of the vacuum magnetic field are studied. It is confirmed that the lateral conducting wall still creates the upper stability zone, where the ratio β of the plasma pressure to the pressure of vacuum magnetic field exceeds the second critical value βcr2, β>βcr2. However, in many cases the upper zone is clamped from above by mirror instability. When the lateral wall is combined with end MHD anchors, a lower stability zone β

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-105002750623&origin=inward&txGid=2c0800ec12afdc0b111f01b7c1945af3

U2 - 10.1017/S0022377824001338

DO - 10.1017/S0022377824001338

M3 - Article

VL - 91

JO - Journal of Plasma Physics

JF - Journal of Plasma Physics

SN - 0022-3778

IS - 2

M1 - E54

ER -