[Amps] Thoriated tungsten lifetime when idling tspa

[Bill Fuqua]

At 12:32 PM 2/9/2007 -0700, John T. M. Lyles wrote:
>Seems I've seen this
> >written up by Eimac or some other manufacturer. Running thoriated
> >tungsten filaments without anode current shortens the life time faster
> >than on-off cycling.

There may be some truth to this because  the filament emission loss is 
related to the filament temperature and the amount of time that it is hot, 
with or with out anode voltage. Running the filament continuously, and 
turning off the anode voltage 50% of the time over the year would shorten 
the life of the tube more than turning off the filament 50% of the time for 
a year.

73
Bill wa4lav