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Registered Member #3282
Joined: Wed Oct 06 2010, 05:01PM
Location:
Posts: 224
would it be possible to run a neon lamp as a geiger tube. lets say we bias the lamp to 40vdc just under the threshold for discharge. would it pick up radiation?
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
The other problem is that they lack a quench gas, so once ionized by radiation they tend to continue to conduct. You can get some really cheap Russian geiger tubes on ebay, the worst of them will work better than a neon lamp.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
The glass is quite thick, probably one reason? (I don't know absorbtion rates)
If quenching is the only problem use a tiny capacitance in parallel charged by a tiny current. I think that neons can 'flash' 100's of Hz, by that time I'd have legged-it (ran far far away!)
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
if you could place the lamp under the right pressure with a small recipient of quenching agent like alcohol or ether for several hours, and slowly (for a couple days) reduce the pressure to atmosphere, you could allow molecules to pass through and add to neon, maybe acting as a quenching agent
this is purely theoretical and an idea of mine...
if you heat the lamp to higher temperature (two to three times ambient) its porosity will raise accordingly
I have a helium-cadmium laser which refills its helium by heating a quartz reservoir, at high pressure
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Quenching is not the issue here, since it is not uncommon for GM tubes to use external electronic quenching to achieve high count rates without pulse pile-up.
The question is whether a given neon bulb has a GM region in which Townsend avalanches can occur - a question most easily determined empirically, I'd say, but I wouldn't be optimistic.
... not Russel! Registered Member #1
Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052
If I remember correctly, neon bulb electrodes are coated with thorium, to make the lamp easier to ignite. That makes them pretty useless for GM service, but interestingly does make them useful as an extremely high value resistor.
Registered Member #1334
Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615
I know very little about GM tubes, but a bit about cold cathode discharge tubes (like neon lamps, nixies etc.)
What might be better to use (more sensitive) is a trigger tube like the Z700U or similar - these have bare electrodes with a fairly high work function, but also can be used with their trigger electrode used as a source of ions for the main anode/cathode gap - the problem with general trigger tubes if that they required some external source of radiation to make their triggering deterministic/reliable - with coated electrodes which have a lower work function, daylight was ok, but uncoated required UV at a minimum but allowed higher current. The trigger electrode circumvents this problem by allowing the creation of enough free ions that the main gap behaviour becomes predictable and much more sensitive even with uncoated electrodes.
Point to make is that the trigger electrode is often coated so the trigger current must be carefully controlled if a negative (quenching) pulse is used in order to prevent the coating sputtering onto the anode and changing the characteristics of the whole tube.
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neon lamp as GM tube
