On Mon, 4 Jan 2010, Scott Dorsey wrote:

Barry wrote:
I know this is a very long shot, but I wondered if anyone has a
geiger-muller tube lurking anywhere?
Perhaps you may know of a supplier or have an old geiger counter that you
may wish to dispose of?


Not sure if you've seen these but...

http://www.goldmine-elec-products.co...?number=G17365

The thing about these is that the glass is designed to block lower energy
radiation. Still, if you want to detect background gamma radiation, it's
not bad. It's probably okay for beta radiation too although you don't know
until you test it.

The market is glutted with Victoreen survey meters. Millions of them were
made for the civil defense folks in the fifties and sixties, and they are
all on the surplus market. They also don't respond well to lower energy
particles, and the scale calibration is useless because the integrator stage
is intended for use in very high radiation environments, but they are very
cheap.

But there was also a need for geiger counters so you could go out and
prospect for uranium. I hadn't given it a lot of thought, until a few
years ago when I found a "magazine" about how to prospect for uranium.
I guess it was published by Fawcett, from the fifties, when it was common
to issue single issue magazines that would be books if they were published
more formally. I have no idea how common the "hobby" was, or how many
geiger counters it sold, but it did seem a big concept for a while.
Robert Heinlein even has some bad guys in one of his juvenile novels
prospecting for uranium on the moon.

There have been solid-state replacements for geiger tubes in recent
decades, but at the moment I can't think of what. Some projects used
existing components that reacted to radiation, but I seem to recall there
were solid-state devices that came along.

Michael VE2BVW

"Kenneth Scharf" wrote in message
...
Geoffrey S. Mendelson wrote:
Kenneth Scharf wrote:

Once upon a time I recall the type CK1026 GM tube. This was about the
size of a 50C5 tube, but with a single pin and an aquadag coating on the
outside of the tube. This tube was used in a geiger counter project
that was in one of Alfred Morgan's 'boys books of radio and
electronics', either the 2nd or 3rd book. There were other types of GM
tubes made, but the CK1026 was one of the least expensive and was used
in many simple radiation detectors.

The ones used in the 1960's radiation detectors and then sold in a pack
of 3 for $1 at Radio Shack in the late 1960's looked like long neon bulbs
with an extra wire comming out of them. I think they were around two
inches
long, but it's been a long time since I've seen them.

Considering that they were designed to detect levels of radiation that
would
only exist if you were close to ground zero and poking your head out of
a shelter in the rubble of an east coast (US) city, for all I know they
really were neon bulbs. :-)

Geoff.

You probably could use a Neon bulb as a radiation detector. You'd have to
keep the tube in the dark (inside a black plastic box) and carefully
adjust the voltage across the tube so it was just below the firing voltage
(need a well regulated power supply). Then an alpha or beta particle
might be enough to trigger the tube into conduction. The sensitivity
would be determined how close to the firing voltage the bias supply was
set.

I recall being unconvinced when a customer complained that the neon
lamp in his old, rotary disk type depth finder would not work at night
unless he shined a flashlight on it. He was absolutely correct, and
as time went on, we found that as all neon flash lamps (mostly NE2's
and NE51's I think) grew old and weak, they required a little extra
external excitation (flashlight worked ok) to light.

Old Chief Lynn, W7LTQ

On Mon, 4 Jan 2010, coffelt2 wrote:


"Kenneth Scharf" wrote in message
...
Geoffrey S. Mendelson wrote:
Kenneth Scharf wrote:

Once upon a time I recall the type CK1026 GM tube. This was about the
size of a 50C5 tube, but with a single pin and an aquadag coating on the
outside of the tube. This tube was used in a geiger counter project that
was in one of Alfred Morgan's 'boys books of radio and electronics',
either the 2nd or 3rd book. There were other types of GM tubes made, but
the CK1026 was one of the least expensive and was used in many simple
radiation detectors.

The ones used in the 1960's radiation detectors and then sold in a pack
of 3 for $1 at Radio Shack in the late 1960's looked like long neon bulbs
with an extra wire comming out of them. I think they were around two
inches
long, but it's been a long time since I've seen them.

Considering that they were designed to detect levels of radiation that
would
only exist if you were close to ground zero and poking your head out of
a shelter in the rubble of an east coast (US) city, for all I know they
really were neon bulbs. :-)

Geoff.

You probably could use a Neon bulb as a radiation detector. You'd have to
keep the tube in the dark (inside a black plastic box) and carefully adjust
the voltage across the tube so it was just below the firing voltage (need a
well regulated power supply). Then an alpha or beta particle might be
enough to trigger the tube into conduction. The sensitivity would be
determined how close to the firing voltage the bias supply was set.

I recall being unconvinced when a customer complained that the neon
lamp in his old, rotary disk type depth finder would not work at night
unless he shined a flashlight on it. He was absolutely correct, and
as time went on, we found that as all neon flash lamps (mostly NE2's
and NE51's I think) grew old and weak, they required a little extra
external excitation (flashlight worked ok) to light.

It's not so much that they needed light, but they could no longer light
up with the old value resistor. Changing the resistor would have worked,
as did the external excitation with a light.

That was the previous point, you put enough current into the neon bulb
so it's not quite lighting up, and then external radiation would excite
it. It's about setting a threshold right below where the bulb lights
up, and then any external excitation ignites it.

Michael VE2BVW

On Tue, 5 Jan 2010 12:28:52 -0500, Michael Black wrote:

On Mon, 4 Jan 2010, coffelt2 wrote:


"Kenneth Scharf" wrote in message
...
Geoffrey S. Mendelson wrote:
Kenneth Scharf wrote:

Once upon a time I recall the type CK1026 GM tube. This was about the
size of a 50C5 tube, but with a single pin and an aquadag coating on the
outside of the tube. This tube was used in a geiger counter project that
was in one of Alfred Morgan's 'boys books of radio and electronics',
either the 2nd or 3rd book. There were other types of GM tubes made, but
the CK1026 was one of the least expensive and was used in many simple
radiation detectors.

The ones used in the 1960's radiation detectors and then sold in a pack
of 3 for $1 at Radio Shack in the late 1960's looked like long neon bulbs
with an extra wire comming out of them. I think they were around two
inches
long, but it's been a long time since I've seen them.

Considering that they were designed to detect levels of radiation that
would
only exist if you were close to ground zero and poking your head out of
a shelter in the rubble of an east coast (US) city, for all I know they
really were neon bulbs. :-)

Geoff.

You probably could use a Neon bulb as a radiation detector. You'd have to
keep the tube in the dark (inside a black plastic box) and carefully adjust
the voltage across the tube so it was just below the firing voltage (need a
well regulated power supply). Then an alpha or beta particle might be
enough to trigger the tube into conduction. The sensitivity would be
determined how close to the firing voltage the bias supply was set.

I recall being unconvinced when a customer complained that the neon
lamp in his old, rotary disk type depth finder would not work at night
unless he shined a flashlight on it. He was absolutely correct, and
as time went on, we found that as all neon flash lamps (mostly NE2's
and NE51's I think) grew old and weak, they required a little extra
external excitation (flashlight worked ok) to light.

It's not so much that they needed light, but they could no longer light
up with the old value resistor. Changing the resistor would have worked,
as did the external excitation with a light.

That was the previous point, you put enough current into the neon bulb
so it's not quite lighting up, and then external radiation would excite
it. It's about setting a threshold right below where the bulb lights
up, and then any external excitation ignites it.

Michael VE2BVW

Probably more a question of voltage supply rather than resistor value,
as unless the neon fires, the drop across the resistor is zero, and so
the resistance value is not controlling the starting.

Peter

"Peter Dettmann" wrote in message
...
On Tue, 5 Jan 2010 12:28:52 -0500, Michael Black wrote:

On Mon, 4 Jan 2010, coffelt2 wrote:


"Kenneth Scharf" wrote in message
...
Geoffrey S. Mendelson wrote:
Kenneth Scharf wrote:

Once upon a time I recall the type CK1026 GM tube. This was about
the
size of a 50C5 tube, but with a single pin and an aquadag coating on
the
outside of the tube. This tube was used in a geiger counter project
that
was in one of Alfred Morgan's 'boys books of radio and electronics',
either the 2nd or 3rd book. There were other types of GM tubes made,
but
the CK1026 was one of the least expensive and was used in many simple
radiation detectors.

The ones used in the 1960's radiation detectors and then sold in a
pack
of 3 for $1 at Radio Shack in the late 1960's looked like long neon
bulbs
with an extra wire comming out of them. I think they were around two
inches
long, but it's been a long time since I've seen them.

Considering that they were designed to detect levels of radiation that
would
only exist if you were close to ground zero and poking your head out
of
a shelter in the rubble of an east coast (US) city, for all I know
they
really were neon bulbs. :-)

Geoff.

You probably could use a Neon bulb as a radiation detector. You'd have
to
keep the tube in the dark (inside a black plastic box) and carefully
adjust
the voltage across the tube so it was just below the firing voltage
(need a
well regulated power supply). Then an alpha or beta particle might be
enough to trigger the tube into conduction. The sensitivity would be
determined how close to the firing voltage the bias supply was set.

I recall being unconvinced when a customer complained that the neon
lamp in his old, rotary disk type depth finder would not work at night
unless he shined a flashlight on it. He was absolutely correct, and
as time went on, we found that as all neon flash lamps (mostly NE2's
and NE51's I think) grew old and weak, they required a little extra
external excitation (flashlight worked ok) to light.

It's not so much that they needed light, but they could no longer light
up with the old value resistor. Changing the resistor would have worked,
as did the external excitation with a light.

That was the previous point, you put enough current into the neon bulb
so it's not quite lighting up, and then external radiation would excite
it. It's about setting a threshold right below where the bulb lights
up, and then any external excitation ignites it.

Michael VE2BVW

Probably more a question of voltage supply rather than resistor value,
as unless the neon fires, the drop across the resistor is zero, and so
the resistance value is not controlling the starting.

Peter

And thus the irritating (and sometimes useful) Neon tube oscillator!

Old Chief Lynn

"Kenneth Scharf" wrote in message
...
You probably could use a Neon bulb as a radiation detector. You'd have
to keep the tube in the dark (inside a black plastic box) and carefully
adjust the voltage across the tube so it was just below the firing voltage
(need a well regulated power supply). Then an alpha or beta particle
might be enough to trigger the tube into conduction. The sensitivity
would be determined how close to the firing voltage the bias supply was
set.

GM tubes don't work quite like that. They have a halogen gas in there as
well to "quench" the conduction caused by the radiation.


--
73
Brian G8OSN/W8OSN
www.g8osn.net

Sparkfun.com sells a 712 end-window geiger tube from LND, Inc. It's
sensitive to alpha and beta particles as well as gamma radiation, and
it's something like $70. They have a complete geiger counter kit which
includes a DC-DC converter to get the 500V for $140.

They currently have a promotion going on which is causing their site to be
hammered, but it should be back to normal in a day or two.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."