Glassblowing #3: A better thermionic diode (opens in new tab)

My last attempt at a vacuum tube technically worked, but not very well because there was a lot of glass between the anode and cathode: Because of this, many any electrons that miss anode and build up on the glass. This negative charge will keep accumulating until it's strong enough to overpower the anode's positive charge. With enough voltage, some current does flow, but a diode that only conducts a microamp at 1000 V is not very useful. On paper, the solution is simple: surround the filament...