Neon Bulb Radiation Detector?
George Steber
Just read in a popular electronics magazine about using a neon bulb as a
radiation detector. The article was based on a design idea by Peter
Lay published in the March 18/02 ELECTRONIC DESIGN, Ideas For Design
where it supposedly received an award.
So I grabbed a handful of neon bulbs of various types NE2, NE2H and so
on and put together a circuit to check out the claim. I used a
precision, well regulated, laboratory HV supply so there would be no
chance of power supply variations causing false indications or
triggering of the neon. I also tried various circuits. In each case I
adjusted the HV until the neon barely lit and then backed off a tiny
amount, usually around one volt, and monitored the output signal across
a resistor in series with the neon with my Tek digital scope. Note that
some neons had a threshold of 67 volts DC while some, like the NE2H, had
a DC threshold of 120 volts.
Sorry to report that there was no firing of the neon bulb for any of the
neon bulb types or circuits I tried. I did notice that my overhead
lights did affect the trigger point on the neon. So I put a light shield
over the test setup. So, as I said, there was no indication whatsoever
of the neon triggering with the threshold voltage set to within 1 volt
of firing. I tried a lot of different combinations too.
So, is this idea bogus or what? I'm leaning in that direction right now.
Can anyone, hopefuly with beta and gamma ray detector experience, shed
some light on this??
As far as the published circuit (www.elecdesign.com) of Lay is
concerned, I'm thinking he had some false triggering because of AC line
voltage fluctuations that weren't adequately filtered and regulated.
George
Spehro Pefhany
<ste...@execpc.com> wrote:
>As far as the published circuit (www.elecdesign.com) of Lay is
>concerned, I'm thinking he had some false triggering because of AC line
>voltage fluctuations that weren't adequately filtered and regulated.
They do absolutely no testing of those design ideas, nor would the
person or two who looks at it necessarily by able to make a judgement.
ISTR that they deliberately insert some radioactive material (in the
gas or in the electrodes) in neon lamps to reduce the trigger voltage.
If so, then probably only relatively high levels of radioactivity
would be distinguishable from the artificially high background.
Here's a clip from one data sheet:
--
DARK EFFECT
When glow lamps are placed in a darkened environment, a phenomenon
called dark effect increases BDV and ionization time. To diminish this
effect, a radioactive additive is blended into the gas.
--
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Chuck Simmons
The simplest radiation detector of my experience was constructed thus. A
block of dry ice was placed at the bottom of a 1 gallon pickle jar (I
knew that pickles had a raison d'etre but I could not find it until
then). The dry ice was covered with a single layer of black felt. A damp
towel was placed over the open top of the pickle jar. A bright light was
aimed at the side of the jar. Secondary cosmic ray particles were then
viewed. The towel may be dipped in isopropyl alcohol as well. It is
called a cloud chamber.
Chuck
--
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons chr...@webaccess.net
Sir Charles W. Shults III
Cheers!
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
John Larkin
An electroscope is simple, but not very sensitive. Poke a piece of
wire through the cork of a bottle; bend the bottom end into a hook,
and suspend an inverted V of foil (thin foil, like from a gum wrapper
is best) inside the bottle.
Charge the protruding wire, and the leaves of the foil V will spread.
Expose it to radiation, and the charge will bleed away and the leaves
will collapse. The effect is very dramatic with a smoke-detector alpha
source.
This is the same general idea as the quartz-fiber dosimeter.
John
Dave VanHorn
uranium oxide fuel pellet 1.5 mRem hot stuff!
Ebay?
George Steber
My tests indicate that it does not work for normal background radiation. I did place some alpha emitter radiators like Am241 next to the neon bulb but due to their nature they won't penetrate the glass of the neon bulb. I don't have any other radioactive sources. The original Lay article did not mention using radioactive material and did not give an indication of how many clicks are generated except to say the "short and quiet noise comes out of the speaker."
I'm sure that a sufficiently strong radioactive source will ionize the neon gas. The question is whether this method is practical for low level monitoring similar to a GM tube. BTW, some devices claiming to be GM counters are really ionization chambers and require an order of magnitude more radiation to be detected.
George
Jim Stockton
>
> Part 1.1 Type: Plain Text (text/plain)
> Encoding: 7bit
Try to find some thoriated welding rod. The lantern mantles available
now don't have any thorium in them any more. The civil defense type
geiger counters seem to have been thresholded for uranium . They barely
register a cobalt 60 source that will drive a scintillation counter
nuts. If you can find a local outcrop of shale that usually contains K T
U salts that are locked in and would make a decent source (100-200 cps
on scintillation detector). You can buy unlicensed sources from Canberra
but they are kind of expensive. A large bottle of KCl could be used but
there isn't a lot of K40 in there. Ash from a coal fired power plant
supposedly contains a fair amount of K40. Clay also contains K U T
salts. Am241 also has a gamma emission at 59.5 kev but you probably
won't see it without a scintillation detector.
Good luck
Jim Stockton
James Meyer
>
>Sorry to report that there was no firing of the neon bulb for any of the
>neon bulb types or circuits I tried.
I doubt that you have a source of particles that will penetrate the
glass envelope of the bulb.
The general scheme is at least 50 years old. There were commercial
microwave oven testers built with neon bulbs biased just short of conduction.
You waved them around door seals to check for leakage. Microwaves go through
glass easily.
Hams use neon bulbs, sometimes without bias, as rf indicators for tuning
up transmitters in the 50 watt or better range.
When I was fixing tube type TV sets for a living, I had a neon bulb
stuck in the end of a plactic wand that I used to see if the horizontal
oscillator was working in sets that had dark screens.
I used an NE-2 to detect static electricity. It was at least as
sensitive as a gold leaf electroscope for static charges. Could turn it on from
a foot away with a plastic comb that I had passed through my hair. Wouldn't
work today though, .... no hair 8-(
I also built some flip-flops from neon bulbs. Never got around to
duplicating the neon bulb adding machine that was printed up in 1960 Pop Tronics
magazine though.
Jim
Rene Tschaggelar
> Neon Bulb Radiation Detector?
>
> Just read in a popular electronics magazine about using a neon bulb as a
> radiation detector. The article was based on a design idea by Peter
> Lay published in the March 18/02 ELECTRONIC DESIGN, Ideas For Design
> where it supposedly received an award.
>
>
In addition to what's been said already :
Since Aplha particles are absorbed in a single sheet of paper, you won't
get them into the tube. The only thing you can measure is an ionized
air molecule, when the charge avalanches. In order to get oxygen or
nitrogen ionized it'll take probably a gamma. The walls of the tube should
be sufficiently thin as not to absorb the gamma already.
Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
James Meyer
>In article <a3326v4tg3lc45j0p...@4ax.com>,
> dated Sat, 01 Mar 2003 19:46:50 GMT,
> Spehro Pefhany, <sp...@interlog.com> says...
>
>
>> ISTR that they deliberately insert some radioactive material (in the
>> gas or in the electrodes) in neon lamps to reduce the trigger voltage.
>> If so, then probably only relatively high levels of radioactivity
>> would be distinguishable from the artificially high background.
>
>In my junk box I have a neon detector, it is the shape and
>size of a pen, with one long electrode in the midle and
>another very short one. I cannot tell wich is the anode and wich
>is the cathode :-)
I seem to recall that the negative electrode is the one which has the
glow surrounding it.
Jim
George Steber
Am241 source, in air, using just a simple ionization chamber charged to 300
volts or so. But the neon bulb approach seemed to have some advantages. But
so far I haven't found any <smile>.
BTW, I should have mentioned in the original post that the neon was to be used
to detect nuclear radiation not microwave or RF radiation. I'm quite familiar
with using the neon to detect microwaves having worked near high power radar
in my younger days.
George
Tim Shoppa
> Neon Bulb Radiation Detector?
>
> Just read in a popular electronics magazine about using a neon bulb as a
> radiation detector. The article was based on a design idea by Peter
> Lay published in the March 18/02 ELECTRONIC DESIGN, Ideas For Design
> where it supposedly received an award.
>
> So I grabbed a handful of neon bulbs of various types NE2, NE2H and so
> on and put together a circuit to check out the claim. I used a
> precision, well regulated, laboratory HV supply so there would be no
> chance of power supply variations causing false indications or
> triggering of the neon. I also tried various circuits. In each case I
> adjusted the HV until the neon barely lit and then backed off a tiny
> amount, usually around one volt, and monitored the output signal across
> a resistor in series with the neon with my Tek digital scope. Note that
> some neons had a threshold of 67 volts DC while some, like the NE2H, had
> a DC threshold of 120 volts.
>
> Sorry to report that there was no firing of the neon bulb for any of the
> neon bulb types or circuits I tried. I did notice that my overhead
> lights did affect the trigger point on the neon.
Your overhead lights produce gamma rays with energies of a few eV's.
So the neon bulb did work as a radiation detector :-).
Tim.
Boris Mohar
>Neon Bulb Radiation Detector?
>
>Just read in a popular electronics magazine about using a neon bulb as a
>radiation detector. The article was based on a design idea by Peter
>Lay published in the March 18/02 ELECTRONIC DESIGN, Ideas For Design
>where it supposedly received an award.
>
Make a neon relaxation oscillator and see if you can detect any
frequency change as it is exposed radiation.
--
Regards,
Boris Mohar
Viatrack Printed Circuit Designs
Fred Bloggs
Peter Lay knows what he's doing, you are misunderstanding the operation
of the neon. You really have two thresholds at play with the neon bulb,
the strike voltage and the maintaining voltage. The strike voltage is
the bulb voltage for very small currents say up to a few uA. As the
current increases beyond a certain threshold, the bulb enters a negative
resistance transition region where increases of current cause the bulb
voltage to drop to the much lower maintaining voltage. Current can also
be increased beyond this region and into a second transition region of
positive resistance followed by a second negative resistance and arc
current region. Therefore your initial set-up should be to adjust
voltage across the bulb into the strike voltage region and just short of
the *current level* for transition into the first negative resistance
region. This will be a current measurement and not a voltage
measurement. Obviously the sensitivity will be a function of the how
close your current bias is to the transition threshold within the strike
voltage region. The interesting aspect of this is that small source
voltage fluctuations produce far less incremental current increase than
an ionizing radiation current pulse, the bulb appears as a voltage clamp
with small incremental resistance and consequently very large
attenuation of current fluctuation to due voltage fluctuations through a
large source impedance. Current induced by ionizing radiation triggers
an avalanche effect to a low maintaining voltage which instantly draws
the maximum available current from the source. As the rectifier
capacitor discharges, the source current falls out of the maintaining
voltage region and the bulb rapidly returns to its steady state in the
strike voltage region. The bulb is *all* about electric field when in
the strike voltage region, so interference from overhead lighting will
obviously produce false triggering.
George Steber
at length on pages 1 and 2 of the GE Glow Lamp Manual in Chapter One "Physics
And Characteristics Of Glow Lamps". Figure 1.1 is particularly good as it
inducates the "Characteristic Curve Of The Neon Lamp" and all of the
interesting regions.
I have been setting up my circuits in accordance with Lay's article on
building a "low cost Geiger detector" as well as others and some of my own. I
have set the voltage to the Townsend region, as well as the breakdown or
firing region and other regions too. I am still not conviced that the neon
bulb can be used as a reliable nuclear radiation (Geiger) detector.
Fred Bloggs wrote:
>
>
> Peter Lay knows what he's doing, you are misunderstanding the operation
> of the neon. You really have two thresholds at play with the neon bulb,
> the strike voltage and the maintaining voltage. The strike voltage is
> the bulb voltage for very small currents say up to a few uA. As the
> current increases beyond a certain threshold, the bulb enters a negative
> resistance transition region where increases of current cause the bulb
> voltage to drop to the much lower maintaining voltage. Current can also
> be increased beyond this region and into a second transition region of
> positive resistance followed by a second negative resistance and arc
> current region. Therefore your initial set-up should be to adjust
> voltage across the bulb into the strike voltage region and just short of
> the *current level* for transition into the first negative resistance
> region. <snip>
Sir Charles W. Shults III
cannot travel far through air, beta is stopped by a thin sheet of paper, and
gamma can penetrate very nicely. Neutrons will go through lots of stuff very
well also.
A neon bulb is only going to be good for detecting gamma and on occasion,
neutrons (from their interactions with other particles) and on rare occasions,
the secondary stuff from alpha or beta impacts on the glass.
Chuck Simmons
>
> cannot travel far through air, beta is stopped by a thin sheet of paper, and
> gamma can penetrate very nicely. Neutrons will go through lots of stuff very
> well also.
> A neon bulb is only going to be good for detecting gamma and on occasion,
> neutrons (from their interactions with other particles) and on rare occasions,
> the secondary stuff from alpha or beta impacts on the glass.
What about secondary cosmic ray events? These give about a 30 to 60
count backgroung in a G-M counter. They are very evident in CCD images.
They are commonly seen in image intensifiers both conventional and
microchannel plate. Secondary cosmic ray events are easily found inside
of quite heavy structures. The glass is nothing.
Fred Bloggs
George Steber wrote:
> I am aware of the theory behind neon bulbs. Most of what you say is
> discussed at length on pages 1 and 2 of the GE Glow Lamp Manual in
> Chapter One "Physics And Characteristics Of Glow Lamps". Figure 1.1
> is particularly good as it inducates the "Characteristic Curve Of The
> Neon Lamp" and all of the interesting regions.
>
> I have been setting up my circuits in accordance with Lay's article
> on building a "low cost Geiger detector" as well as others and some
> of my own. I have set the voltage to the Townsend region, as well as
> the breakdown or firing region and other regions too. I am still not
> conviced that the neon bulb can be used as a reliable nuclear
> radiation (Geiger) detector.
>
>
Taking a second look at the Electronic Design print of the circuit, it
is now clear that the schematic is in error. The bulb series resistor
should be in the range 100->1K and not the values shown. Now when the
bulb fires the current will be in the 10mA region, the zener is cut-off,
and the capacitor discharges to a low enough voltage for bulb quenching
with a 100ms time constant. You don't have any gain with the circuit
shown. Of course the bulb will be a reliable detector, but the question
is the sensitivity. Does the GE manual state anything about the gas
composition and density?
Spehro Pefhany
Here's a bit of information from a Japanese lamp maker, nothing
quantatative and no mention of the radioactive gas additive that the
other manufacturer said they added.
http://www.toyokawadenki.co.jp/LAMP%20USU(2).htm
Real GM tubes have a quenching gas additive (halogen or something like
that) as well.
George Steber
neon relaxation oscillator circuits that have the DC supply voltage adjusted to
just below oscillation. When an external event or power supply variation occurs,
it can trigger the neon.
In my experiments I have found that I can trigger the neon (into oscillation) by
moving my hand, from as far away as 12 inches. This is a electrostatic effect
which seems to greatly affect the neon. Also placing a small 1/2 inch metal disc
near the neon can trigger it on, so that it oscillates.
I have filed away the glass of the neon bulb, thining it, to make it more
transparent to alphas but no results with Am241 or Po210.
My results seem to correspond to those in the GE Glow Manual where it discusses
external effects on pages 5 and 6. I will quote some of them below.
Some parts From GE Glow Manual follow:
DARK EFFECT
Since the cathode surface material is photosensitive, its emission can be
greatly reduced by the absence of illumination. Glow lamps in complete darkness
become erratic....
ELECTROSTATIC FIELDS
Electrostatic fields noticeably affect glow lamps. For example, if the voltage
across the lamp is held below the static breakdown voltage, the appearance of an
electrostatic field in proximity to the lamp can cause it to start....
RADIATION EFFECTS
Tests have been made on glow lamps in operation with sawtooth oscillators under
continuous gamma radiation up to levels of 1.2 x 10 to 5th Roentgen per hour. No
appreciable or consistent changes were observed in the frequency, firing voltage
or extinguishing voltage of the glow lamps that were tested. The results from
these tests and other reports indicate that short time operation of glow lamps
is not appreciably affected by radiation even though the radiation may reach
rather high levels of intensity. ....
MISCELLANEOUS
Glow lamps are also sensitive to the presence of high-intensity radio frequency
fields since the gas will glow in such a field.
End of GE Manual quotes.
As is seen above there are many effects that cause a neon bulb to fire. Many of
them are very common, such as electrostatic fields or RF and can cause glowing
of the bulb. In addition GE did not find gammas to seriously affect the neon.
Consequently I am still dubious about the use of a neon bulb as a "Geiger" type
radiation detector. I am in process of obtaining some radioactive material with
beta and gamma emmisions for further testing, but I am not optimistic about
producing results from it.
George
John Larkin
wrote:
> I am still not conviced that the neon
>bulb can be used as a reliable nuclear radiation (Geiger) detector.
>
>
It obviously can't. If it were a reliable radiation detector, somebody
would have commercialized its use sometime in the last 100 years.
Instead, people keep going to the trouble to make expensive Geiger and
scintillator detectors.
John
Mark Zenier
George Steber <ste...@execpc.com> wrote:
>I am aware of the theory behind neon bulbs. Most of what you say is discussed
>at length on pages 1 and 2 of the GE Glow Lamp Manual in Chapter One "Physics
>And Characteristics Of Glow Lamps". Figure 1.1 is particularly good as it
>inducates the "Characteristic Curve Of The Neon Lamp" and all of the
>interesting regions.
>
>I have been setting up my circuits in accordance with Lay's article on
>building a "low cost Geiger detector" as well as others and some of my own. I
>have set the voltage to the Townsend region, as well as the breakdown or
>firing region and other regions too. I am still not conviced that the neon
>bulb can be used as a reliable nuclear radiation (Geiger) detector.
Especially after you read the paragraph on Radiation Effects on page 6.
Mark Zenier mze...@eskimo.com Washington State resident
John Popelish
(snip)
> As is seen above there are many effects that cause a neon bulb to fire. Many of
> them are very common, such as electrostatic fields or RF and can cause glowing
> of the bulb. In addition GE did not find gammas to seriously affect the neon.
> Consequently I am still dubious about the use of a neon bulb as a "Geiger" type
> radiation detector. I am in process of obtaining some radioactive material with
> beta and gamma emmisions for further testing, but I am not optimistic about
> producing results from it.
Have you ever thought of testing an ordinary incandescent light bulb
that has a blown filament? Can low pressure nitrogen gas avalanche
under high voltage the same way neon does? I have seen a beautiful
pink discharge in light bulbs when they are held near tesla coils.
--
John Popelish
Thomas
> The greatest obstacle is the thick glass envelope itself. Alpha particles
> cannot travel far through air, beta is stopped by a thin sheet of paper, and
> gamma can penetrate very nicely. Neutrons will go through lots of stuff very
> well also.
Well, there is a reason a Geiger tube has a really horrible gas filling with the
halogen mixed in - this stuff reacts to your electrodes, and if it could be
missed it would probably be left out.
I guess the neon bulb just lights, doesn't get quenched, and stays on, where a
Geiger tube would not ignite.
Some interesting thoughts are on http://www.techlib.com/science/ion.html - ion
chambers, and the suggestion of using a neon bulb as a light dependent variable
resistor.
Thomas
Thomas
> Have you ever thought of testing an ordinary incandescent light bulb
> that has a blown filament? Can low pressure nitrogen gas avalanche
> under high voltage the same way neon does? I have seen a beautiful
> pink discharge in light bulbs when they are held near tesla coils.
I think there is something with the quenching. A photoelectron or thermal noise
will ignite the neon, but maybe not the GM tube. At least, you'd hope it would
give a lower pulse than a real 'hit'.
Thomas