The first LIVE ignition test of the AIS-GDN1 Glow-Discharge Hollow-Cathode Neutralizer is set for tomorrow 10am EST (-4 UTC)! Join me as I attempt ignition of this highly unconventional micro neutralizer with Adamantane fuel and only a few watts of power! Link to the livestream can be found HERE.
This will be the first time I have fired up this design. While I ran some simulated hollow cathode test during the 3rd preliminary Adamantane sublimation/glow-discharge test to achieve a successful plume (recap and overview HERE), this is a bit different, since it will be the actual full hollow cathode, rather than the glass discharge test cell.
There are some unique differences of the GDN1 from standard hollow cathodes in EP. This design is based off of hollow cathode e-beam sources utilized in particle physics/experimental industrial processing applications, which is something I have surprisingly not come across in EP.
The hollow cathode itself is literally just a hollow stainless cathode – no heaters, no LaB6 or BaO dispenser inserts, no RF excitation. Rather it operates at significantly higher voltages (several kV) establishing a plasma discharge between the cathode/anode for extraction.
These systems can be run both DC and pulsed, anywhere from a few watts of power and uA of current to MWs of peak power at kA of current. They are also incredibly versatile in that they can operate at quite high pressures to produce e-beams, and can be run with any gas source. This particular design is pushing the geometric limits of what can be sustained for a glow discharge at my target operating pressure. Unfortunately I don’t have any data on the Paschen curve for Adamantane, so I am betting on it being similar to air (non-noble complex gas).
The biggest unknown going into this test will be fuel flow. The GDN1 will be mounted to the EHT1 with all feed holes open simulating full fuel flow to the thruster and neutralizer. Based on prior tests I should be able to achieve discharge as long as enough fuel gets to the GDN1. Only one way to find out!