Re: TC in a vacuum ... Re: TC vs Electron Gun

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jimlux-at-earthlink-dot-net>
> 
> Actually, we do something like running a TC in a vacuum when we run RF
> breakdown tests in a large (the largest?) clear bell jar at JPL.  Granted, I
> don't recall anyone running tests at 100 kHz, but at 400 MHz, you bet.

	Are you talking about looking for multipactor discharge?  If so, that's
an old subject for me and I had a NASA contract to investigate
"Multipactor Discharge in Space Electronics Systems" way back in the mid
1960's. I got bitten with that in building a  400 MHz bandpass filter
for a 10 watt transmitter we built for the Grumman OAO, which I guess
most people have forgotten about. Turned out that the coaxial resonators
I built had perfect dimensions for resonance at the voltages at which it
operated. About the same time JPL had a problem with multipactor in the
transmitters for Ranger and a kid at JPL named Richard Woo apparently
made a career studying the subject.

	This is just a little off the subject of TC's, but in the course of the
study I found out that people had been having big troubles with
multipactor for many years, from 50 MHz in a big Harvard linear
accelerator to windows in TWT's, etc.  I talked to a lot of those guys
and they had about the same story - it had been a total surprise to them
and they had to go to incredible troubles to get rid of it.  Turns out
that one-sided multipactor is also possible.

	As for the TC in space, the spacings for multipactor resonance would at
100 KYz would be of the order of 7.5 meters, and it is possible that
multipactor might be experienced, although the normal operating voltage
of a TC would probably be above the maximum allowable for multipactor. 
Of course, in the time when the secondary voltage was building up
resonance might occur, in which case the voltage probably wouldn't go
any higher and something would melt.

Ed