Group Ion gun design - ideas only

[walter_b_marvin]

what about good old carbon as a filliment? Inexpensive, high temp, available

[3l]

Hi Mark:

It is simple enough to thoriate tungsten just coat he filament in a slurry of thorium nitrate . The slurry is a pile of thorium nitrate wetted until it is paste like. I applied the paste to the filament with an artists brush. I have a separate conflat rig to treat and pump away the nitrogrn dioxide formed by heat decompostion of the Thorium nitrate at 800 degrees. (to allow the pump ample time to remove the N2O ..pump to 1 torr then turn on the filament) I used a crudded up piece of conflat that could not be used for anything else as the pumping body. A chemical trap of dry NaOH saves the pump from corrosion. It is well worth all the fuss. it almost doubles the emmision of electrons from the filament. In the old radio tube days a small glass vial would be used for thoriation. Simply dip the filament in and you are done. But these days I mix up tiny batches on a jar lid and paint it on. Powdered tungsten mixed with thorium nitrate works better in a pressed solid. Molybdem is prefered for production units (cost) but requires loads of processing equipment , tungsten can be pressed in an automotive press and heated in a metalurgical furnace. Thanks for the link on pressed thoria work. My reference was a 1920's physics book,but this 1950's reference is very detailed and a good read.

Happy Fusoring!
Larry Leins
Fusor Tech

[MARK-HARRISS]

Ahh thanks for that cool tip Larry. Just a quick question: how soluble is ThNO3?, is it considered toxic apart from the obvious properties?.


regards
Mark H

[3l]

Hi Mark:

Thorium nitrate will gather water on sitting.
The stuff loves water just like most inorganic nitrates. Thorium nitrate you would will get from a yard sale will be a solid lump if it has been opened a lot. I bought mine from a recycler and the powder is pure as driven snow. One of the permitted uses is for thoriating filaments but who knows these days how long it will last?. The real hazard is opening a bottle in your face, thorin gas is as bad as radon gas. For god's sake don't suck up the powder!

Happy Fusoring!
Larry Leins
Fusor Tech

[Richard Hull]

A single supply ion source would be a field emission type and would never produce decent ion currents.

The simple fusor does this.

It could be considerably enhanced if the walls could be coated with millions of tiny tungsten needles in a vertically distributed fuzz.

Richard Hull