TY - JOUR

T1 - Influence of the shape of a conducting chamber on the stability of rigid ballooning modes in a mirror trap

AU - Zeng, Qiusun

AU - Kotelnikov, Igor

N1 - This work has been done in the framework of ALIANCE collaboration [\u2013]. It was supported by Chinese Academy of Sciences President\u2019s International Fellowship Initiative (PIFI) under the Grant No. 2022VMA0007, Chinese Academy of Sciences International Partnership Program under the Grant No. 116134KYSB20200001, and the HFIPS Director Fund under the Grant No. 2024YZGH03.

PY - 2024

Y1 - 2024

N2 - MHD stabilization of flute and ballooning modes in an axisymmetric mirror trap is studied under the assumption of strong finite Larmor radius effect that suppresses all perturbations with azimuthal numbers m ⩾ 2 and makes the m = 1 mode ‘rigid’. The rigid mode can be effectively suppressed using perfectly conducting lateral wall without any additional means of stabilization or in combination with end MHD anchors. Numerical calculations were carried out for an anisotropic plasma produced in the course of neutral beam injection into the minimum of the magnetic field at the right angle to the trap axis. The stabilizing effect of the conducting shell made of a straightened cylinder is compared with a proportional chamber, which, on an enlarged scale, repeats the shape of the plasma column. It is confirmed that for convincing wall stabilization of the rigid modes, the plasma beta (β, the ratio of the plasma pressure to the magnetic field pressure) must exceed some critical value β cr 2 . When conducting lateral wall is combined with conducting end plates imitating MHD end anchors, there are two critical betas and, respectively, two stability zones β < β cr 1 and β > β cr 2 that can merge, making the entire range 0 < β < 1 of betas allowable for stable plasma confinement. The dependence of the critical betas on the plasma anisotropy, mirror ratio, width of the vacuum gap between the plasma column and the lateral wall, radial pressure profile and the axial magnetic field profile is examined.

AB - MHD stabilization of flute and ballooning modes in an axisymmetric mirror trap is studied under the assumption of strong finite Larmor radius effect that suppresses all perturbations with azimuthal numbers m ⩾ 2 and makes the m = 1 mode ‘rigid’. The rigid mode can be effectively suppressed using perfectly conducting lateral wall without any additional means of stabilization or in combination with end MHD anchors. Numerical calculations were carried out for an anisotropic plasma produced in the course of neutral beam injection into the minimum of the magnetic field at the right angle to the trap axis. The stabilizing effect of the conducting shell made of a straightened cylinder is compared with a proportional chamber, which, on an enlarged scale, repeats the shape of the plasma column. It is confirmed that for convincing wall stabilization of the rigid modes, the plasma beta (β, the ratio of the plasma pressure to the magnetic field pressure) must exceed some critical value β cr 2 . When conducting lateral wall is combined with conducting end plates imitating MHD end anchors, there are two critical betas and, respectively, two stability zones β < β cr 1 and β > β cr 2 that can merge, making the entire range 0 < β < 1 of betas allowable for stable plasma confinement. The dependence of the critical betas on the plasma anisotropy, mirror ratio, width of the vacuum gap between the plasma column and the lateral wall, radial pressure profile and the axial magnetic field profile is examined.

KW - LoDestro equation

KW - MHD stability

KW - ballooning modes

KW - compact axisymmetric toroid

KW - gas-dynamic trap

KW - wisconsin HTS axisymmetric mirror

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85196018860&origin=inward&txGid=fa6aae5c02a9b5fc1a8d457faddad388

UR - https://www.mendeley.com/catalogue/7923f844-0a57-3370-b1f2-5ec838a8c07b/

U2 - 10.1088/1361-6587/ad4f10

DO - 10.1088/1361-6587/ad4f10

M3 - Article

VL - 66

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

SN - 0741-3335

IS - 7

M1 - 075020

ER -