I have NO idea whats the use of Carbon since #62 !?
Before I thougt you are looking for a LV rod, the thing between diode's cathode and air gap inside Gray Tube.
And for this purpose I thougt of a spark plug, a conventional, resistor-type spark plug.
Between middle electrode right and helical steel spring you can see a (carbon?) resistor with ~15mm length. In case of this plug it had some kOhm (5(?)kOhm) resistance.
Every standard plug got this resistance. We can measure it between middle electrode down and up.
Why not using plug as a LV rod? Isnt this the aim?
Aaron or Admin, if I am complete wrong with purpose of carbon here, please remove my contri asap!