Stability of non-neutral plasma in a magnetic dipole trap
ORAL
Abstract
A non-neutral plasma can be confined in a global thermal equilibrium state as well as a local
thermal equilibrium along magnetic field lines in a magnetic dipole trap [1]. While global ther-
mal equilibrium states are maximum entropy states and hence guaranteed to be stable, local
thermal equilibria can support growing diocotron modes [2]. These modes were studied to a
great extend in the homogeneous magnetic field of a Penning-Malmberg trap [3]. We will focus
on the inhomogeneous magnetic field of a z-pinch, which serves as an approximation of the
vicinity of a levitated coil. This implies two differences in comparison to a Penning-Malmberg
trap. First, grad-B and curvature drifts influence the mode. Second, arbitrary non-neutrality can be
studied. In particular, different fractions of electrons and positrons are considered. This study is
motivated by APEX, "A Positron-Electron eXperiment" in a levitated dipole trap [4].
thermal equilibrium along magnetic field lines in a magnetic dipole trap [1]. While global ther-
mal equilibrium states are maximum entropy states and hence guaranteed to be stable, local
thermal equilibria can support growing diocotron modes [2]. These modes were studied to a
great extend in the homogeneous magnetic field of a Penning-Malmberg trap [3]. We will focus
on the inhomogeneous magnetic field of a z-pinch, which serves as an approximation of the
vicinity of a levitated coil. This implies two differences in comparison to a Penning-Malmberg
trap. First, grad-B and curvature drifts influence the mode. Second, arbitrary non-neutrality can be
studied. In particular, different fractions of electrons and positrons are considered. This study is
motivated by APEX, "A Positron-Electron eXperiment" in a levitated dipole trap [4].
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Publication: [1] Steinbrunner, P., et al., "Thermal Equilibrium of Collisional Non-Neutral Plasma in a Magnetic Dipole Trap"<br>Journal of Plasma Physics 89 (2023)<br>[2] Levy, Richard H. "Diocotron instability in a cylindrical geometry." The Physics of Fluids 8.7 (1965)<br>[3] Davidson, Ronald C. Physics of nonneutral plasmas. World Scientific Publishing Company, 2001.<br>[4] Stoneking, M. R., et al. "A new frontier in laboratory physics: magnetized electron–positron plasmas." Jour-<br>nal of Plasma Physics 86.6 (2020).
Presenters
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Patrick Steinbrunner
Max Planck Institute for Plasma Physics
Authors
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Patrick Steinbrunner
Max Planck Institute for Plasma Physics
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Thomas M O'Neil
University of California, San Diego