The Polaris Linear Plasma Device

Abstract

We report the construction of Polaris, a new linear plasma device with an axial magnetic field dedicated to research and education at the American University of Beirut in Lebanon. The goal is to initiate the investigation of topics related to basic magnetized plasma physics and nuclear fusion. We discuss the novel technical solutions found to set up various components of the device. We start with the magnetic coils where we use power cables to generate the required axial magnetic field. They are included in a stainless steel case for water-cooling. Then, we present the vacuum and the gas inlet systems with which we control the neutral pressure. The way we manufacture the water-cooled radio frequency (RF) antenna allows the production of a variety of designs. Polaris is thus built to operate in a steady state. Using a reciprocating Langmuir probe, we determine the plasma properties as a function of the various control parameters. As the plasma remains in the “blue mode,” we show that the increase in the main magnetic field leads to an increase in the density but a decrease in the plasma temperature. The increase in neutral pressure yields the same effects. However, the increase in RF power leads to an increase in both density and temperature. Finally, plans for future investigations are briefly described.