Trapped-Particle-Mediated Asymmetry Induced Transport and Damping

Recent experiments have characterized 6 transport and damping effects caused by trapping separatrices. Here, pure electron plasma columns have a trapping separatrix created by an applied ``squeeze'' voltage. The experiments have now established that this separatrix 1) damps the novel ``Trapped Particle Diocotron Mode''; 2) damps $m_\theta >0$, $k_z > 0$ Langmuir (plasma) modes; and 3) adds a new dissipative term in resonant 3-wave couplings.\footnote{A.A.~Kabantsev {\it et al.}, Phys.~Rev.~Lett. (Aug.~2008).} When external confinement asymmetries such as magnetic tilt are added, the separatrix 4) damps $m_\theta > 0$, $k_z =0$ diocotron modes; 5) damps $m_\theta = 0$, $k_z > 0$ Langmuir modes; and 6) causes bulk plasma expansion and loss. Initial theory analyzed ``collisional'' separatrix transport scaling as $\sqrt{\nu_{\mathrm{ee}} }$; but recent theory and experiments characterize ``chaotic'' separatrix transport when the separatrix is not $\theta$-symmetric. The experimental scalings for all 6 effects are unambiguous; and the different $B$-scalings for collisional and chaotic separatrix transport may explain the commonly observed bulk expansion rate $\nu_P \propto B^{-1.4}$.