The HelCat basic plasma science device

Abstract

TheHelicon-Cathode(HelCat) device is a medium-size linear experiment suitable for a wide range of basic plasma science experiments in areas such as electrostatic turbulence and transport, magnetic relaxation, and high power microwave (HPM)-plasma interactions. The HelCat device is based on dual plasma sources located at opposite ends of the 4 m long vacuum chamber – an RF helicon source at one end and a thermionic cathode at the other. Thirteen coils provide an axial magnetic fieldB⩾ 0.220 T that can be configured individually to give various magnetic configurations (e.g. solenoid, mirror, cusp). Additional plasma sources, such as a compact coaxial plasma gun, are also utilized in some experiments, and can be located either along the chamber for perpendicular (to the background magnetic field) plasma injection, or at one of the ends for parallel injection. Using the multiple plasma sources, a wide range of plasma parameters can be obtained. Here, the HelCat device is described in detail and some examples of results from previous and ongoing experiments are given. Additionally, examples of planned experiments and device modifications are also discussed.

ExB flows for high-throughput plasma mass separation

“…The end-electrode biasing data with plasma parameters closest to those required for plasma separation are arguably those obtained by Gilmore et al in the Hel-Cat helicon plasma (n ∼ 10 13 ) with a single set of ringelectrodes 98 . However, owing to the different scope of this experiment (turbulence suppression), only data on the effect of a global biasing of the electrodes set are available.…”

Negative electric potential in a cylindrical plasma column with magnetized electrons

“…The answer to this question is usually that if the electrons are magnetized, then the electrode potential will be reproduced with good accuracy along the magnetic field line. However, in a number of experiments, this has not been confirmed [19,20], and the answer to this question is more complicated. This paper shows that, for a fixed voltage on the electrodes, the value of the plasma potential is influenced by such quantities as magnetic field, the density and type of neutral particles, temperature and density of electrons, as well as the geometric dimensions of the system.…”

Emergent kink stability of a magnetized plasma jet injected into a transverse background magnetic field

“…The plasma jet is formed and launched by a compact magnetized coaxial gun, [31] and the background magnetic field is produced in the Helicon-Cathode (HelCat) linear plasma device at the University of New Mexico. [32,33] The injection results in several observed phenomena: (1) when launching the plasma jet into vacuum, a classical n = 1 kink instability is observed, consistent with prior work; [15,16] (2) when injecting the jet into a transverse background magnetic field, a 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 more-stable jet is observed; and (3) analysis of magnetic-field measurements and high-speed-camera images during the injection indicate that the transverse background magnetic field exerts a magnetic tension force on the jet, allowing the formation of extended-length, kink-free jets. Although, the measured safety factor is below unity, implying kink instability, we show that the stability is a result of an emergent sheared axial flow due to the tension force of the background field acting on the jet.…”