Glassblowing #3: A better thermionic diode

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 in anode. This shields it against the influence of any accumulated charge and allows continuous current flow: In practice, building something something like this is tricky. There are the three wires that must be precicly aligned while being sealed through hot glass. For my tube, I started by attaching the leads to a chunk of scrap glass which keeps them aligned throughout the process: The internals can be attached on one side of the glass, and the other side can be sealed in an envelope without…