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Notes:
When we apply about 400V negative to the magnet, a DC glow discharge is initiated around the magnet. The discharge is self-limiting, and after igniting draws only micro-amperes of current. When the magnet is biassed negative, electrons are expelled, ionize the neutral gas, and form ions that circulate around the magnet in a trapped ring. We have movies of the discharge, which under some conditions can be very dynamic, but for this purpose we adjust the voltage for the pressure to achieve a stable pink glow around the magnet (caused by nitrogen plasma). These pictures were taken through the glass port with a $100 Webcam. They were bright pink, but the CCD camera saturates to white. Several frames are shown, side views at the left, and top views on the right. The disk of plasma is confined to the equatorial plane, the thicker disk at the top was taken at 200 mTorr, with decreasing pressure downward to about 30mTorr. One can see that the disk becomes thinner and larger when the collisions with the neutral gas are reduced. The blue glow, seen at higher pressures, is electon-impact ionization of the neutral gas, whereas the pink glow is ion-neutral impact.
On the right hand side is shown a sequence of frames from an oscillation of the discharge, caused by positive feedback of the circulating ions. Gradually the ion density builds up until it triggers a plasma instability that dumps 90% of the plasma and begins over again.
We demonstrate here that a magnetized plasma generated with a DC electric field is constrained to a thin sheet, much as Yokota found for a spinning magnet. The next step is to add dust.