Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Vacuum Tube Filaments
Date: Nov 10, 2:51 pm
Poster: d.preston

On Nov 10, 2:51 pm, d.preston wrote:

>I have had discussions with old ITT tube lab folks and some NRL gurus of custom vacuum tube manufactury. They advised the 5U$ specifically as one which will deteriorate very little if the fils are taken just prior to use for transfer to air.
>I would have to "flash" the filaments and if done well, they should be almost as good as new in a fusor. The key is to avoid the water/oxygen- tungsten cycle common to degrading tungsten and vacuums in tubes.
>Richard Hull

I am guessing that tube you are speaking of has an oxide coated filament.

The filament is coated with a mix of barium carbonate, strontium carbonate, and calcium carbonate (and depending on manufacturer preferences possible with a small addition of strontium nitrate or an alkali azide)

The 'flashing' of a filament with emmitter coating can only be done ONCE. In this proceedure you basically thermally decompose the chemical coating and depending on application may also react the byproducts with a specific gas or ionized gas. filaments are then further 'aged' in which complex reactions occur, ie. electrolytic migration into host material, O2 binding, etc...

you can not remove this emmitter from the tube and then REactivate it.

filaments and emmission chemicals are basically inexpensive and available why go through the trouble to fudge it...

the filaments must, i would think be easily available and changeable for your fusors given the poor vacuum levels. High efficiency emmitters will be damaged unless properly maintained.