Superbanana transport in the collisional heating of a plasma column forced across a squeeze potential

• Published in: Physics of plasmas 2017-11, Vol.24 (11)
• Main Author: Dubin, Daniel H. E.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/1.5001062

When weakly collisional plasmas have locally trapped particle populations, perturbations to the plasma equilibrium (such as waves or static field-errors) can induce phase-space discontinuities in the particle distribution function that strongly enhance entropy production, plasma loss, and wave damping via superbanana transport. Here, this paper presents a simple version of this superbanana transport process, wherein a plasma is heated as it is slowly forced back and forth across a squeeze potential (at a frequency ω that is small compared with the particle bounce frequency). The squeeze potential traps low-energy particles on either side of the squeeze, but particles with higher energy can pass through it. Trapped and passing particles have different responses to the forcing, causing a collisionless discontinuity in the distribution function at the separatrix between the trapped and passing particles. Expressions for both the adiabatic and non-adiabatic distribution functions are presented, and the heating rate caused by collisional broadening of the separatrix discontinuity is derived. The heating rate is proportional to √νω , provided that ν