[AMPS] Network analysis of suppressors

[Michael Tope]

Tom and Rich, please see my comments below:


----------
From: 	Tom Rauch[SMTP:w8ji@contesting.com]
Reply To: 	W8JI@contesting.com
Sent: 	Sunday, March 05, 2000 4:39 AM
To: 	AMPS; measures
Subject: 	Re: [AMPS] Network analysis of suppressors


Hi Rich,


> >This almost sounds like your theory that photons arriving from outer
> >space can make amplifiers on standby explode because the photons hit the
> >amplifier so hard they make the standby relay arc, and the arcing relay
> >starts a parasitic in what is an otherwise stable amplifier that is just
> >sitting there on standby!
> 
> Borrow a geiger counter, Mr. Rauch, and tune in on what's happening on the
> upper frequencies.  Be not surprised if you occasionally encounter some
> humungous signals.

Rich or Tom, please forgive me if I misrepresent any of your
claims as I haven't been following this debate very closely
and hence am not fully versed in the details of your respective
positions. Regarding the idea that radiation single events can 
cause significant current to flow in a high power vacuum tube, 
this seems unlikely to me. First of all, the only place I know
of where radiation single event upsets (SEUs) are of great 
concern, is in space applications and military applications. 
In the case of military applications, we haven't to the best 
of my knowledge any reason for concern, as nuclear weapon 
detonation appears to be a rather rare event (perhaps hams 
in Nevada have a higher rate of 8877 failures). In terms of 
space related SEUs, from what I have seen the, devices that 
are effected tend to be integrated circuits (microprocessors, 
PICs, etc) with very compact geometries (on the order of microns). 
Unless latch-up occurs, these events are generally non-destructive.  

Although, a high energy particle could conceivably strike the 
cathode of a high power vacuum tube and knock loose some 
electrons, it would seem that this would pale in comparison 
to the number of free electrons being produced by thermionic 
emission. Unfortunately I don't have training in this area
(high energy physics), so this is only a guess on my part. I do 
know that in photomultiplier tubes, this is the mechanism that 
is at work. A photon strikes the PMT cathode and knocks loose 
and electron. This electron then gains kinetic energy from the 
electric field applied to the anode, until it collides with a 
subsequent cathode. At this point several free electrons results 
from this secondary event. This process continues until the 
original photon absorption has multiplied itself into a barrage 
of free electrons zooming toward the anode. 

As I said before, for this kind of radiation event to be 
significant in a high power vacuum tube, the number free electrons 
created by the radiation event would have to be on the same ordern 
as the number of electrons created by thermionic 
emission. If one could still make a case for this sort of 
thing (I think that this is unlikely), the hypothesis could be
tested by exposing the amplifier in question to the appropriate 
radioactive source while simultaneously monitoring anode current.


Just my $.02

Mike, W4EF.............


The detector in a geiger counter is specifically designed to respond 
to photons (it uses pressurized gas) when exposed to radiation. 
Even when exposed to high levels of background radiation current 
is in picoamperes.

You are proposing that a high vacuum tubes respond with many 
amperes of current.

If that is the case geiger counters would work better with 3-500Z 
detectors than with gas-filled geiger-muller tubes.

Please explain the apparent discrepancy between your theory and 
how things really work.


73, Tom W8JI
w8ji@contesting.com

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