Build a Pocket Ionizing Radiation Detector (PIRD)

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In this instructable I will be demonstrating how to build a pocket radiation detector or "PIRD." The parts for this radiation detector will all be salvaged (that means no pricey GM tube off of ebay), but building will require steady hands and alot of patience! This is a "clicking" radiation detector, unlike many other DIY versions without a Gieger-Muller tube out there, and I have yet to see anyone try this concept and/or make one like it. Although it may not be as sensitive or practical as a standard geiger counter, it does detect background radiation (most likely gamma rays). Similar concepts are seen on the CERN website, demonstrating the potential to detect both alpha rays and background radiation: (http://teachers.web.cern.ch/teachers/archiv/hst2000/teaching/expt/new/new.htm) and on youtube (http://www.youtube.com/watch?v=RzglpP3D2tQ).

Here is a video testing it using a small amount of radioactive Americium found in a smoke detector:

Step 1: How it Works

This geiger counter works on similar principles that any other ordinary geiger counter works on. Essentially there is a small gap between two wires - a high dc voltage is applied to both wires, and when an ionizing particle moves between the wires, an ion channel is created and electrons arc across the wires, creating an audible "click" on a radio. Normally, the gap is inside of what is called a "geiger muller tube," where gases ideal for ionization are held for increased sensitivity. With this geiger counter, the absence of gases ideal to ionization is made up for by placing the wires in closer proximity to one another (so close that to the human eye they appear to be touching). The process of slowly moving the wires closer to one another is called "spark gap quenching".

Comments

[chocokitti]

The tips of the brass screws I used seem to corrode very quickly. It sparks frequently at first but tapers off and after several seconds it does not work at all. Anyone know what I'm doing wrong?

[techno guy]

There is the possibility that when the screws corrode, it creates some kind of residue or something that acts as an insulator, you might want to check that out.

[mammasboy]

Does the PIRD have much range? in the video the Americium was right next to it, at kind of ranges can it detect radioactive materiel's?

[sciman1]

why not make a simple wooden bracket to hold two small machine thread srews.
kinda like a ~||_||~ u shaped bracket with the screws from either side.
then you could pretty simply just twist in one of the bolts till it "auto quenched"
sand the tips of the srews to remove any burrs... DONE.

[Maters]

Nice instructable but the name is funny for me cuz PIRD in my language means - to fart.

[yellowdart31]

The spark gap quenching could be accomplished easily using an insulating bracket and two finely threaded screws facing each other (tip to tip). Such a configuration would also lend itself more easily to recalibration.

[imshanedulong]

I was thinking something like wires held in by screws to calibrate, but this sounds much easier!

[kelseymh]

That is a really awesome I'ble! I wish I had seen it before Randy, so I could get the glory of Featuring it :-)

I had a bit of trouble following the pictures and descriptions -- you might consider using the "image notes" to identify exactly where in each picture we should focus.

One comment about your "ambient air" G-M counter. You note that when properly aligned, the counter should discharge every minute or two. That's consistent with sea-level cosmic ray rates in the Northern Hemisphere. I wonder if you could get a more quantitative calibration using an Am-241 source scavenged from a smoke detector?

[TheHomebrewGuru]

Video added

[kelseymh]

Nicely done. And a good demonstration that your device really does work to detect ionizing radiation. Thanks!

[TheHomebrewGuru]

I'll try to get my hands on some soon

[jiovine]

Hi, I like your project. However I am not convinced you're detecting gamma radiation. If you like to verify the function of your detector, it's a pretty straight forward test. Bring a radioactive source close to your detector. If it is detecting radioactivity you ought to see and hear an uptick in the number of radioactive particles detected when the source is close by.

[TheHomebrewGuru]

Video added

[TheHomebrewGuru]

http://teachers.web.cern.ch/teachers/archiv/hst2000/teaching/expt/new/new.htm

[TheHomebrewGuru]

I don't have any radioactive samples, I'll try to get my hands on some Americium. But judging by the fact that I only hear the clicks once or twice every couple on minutes, it's a safe bet. Also, a similar idea was published on the CERN website as an educational experiment for use in detecting gamma radiation

[magranger15]

Go to a hospital and see if you can pick some up from X-ray those cancer treatment rooms.

[jiovine]

Spark detectors can detect alpha particles but not beta, gamma or x-rays. If you look at this youtube video you can see a video of a alpha particle spark detector I built a while ago.

http://www.youtube.com/watch?v=RzglpP3D2tQ

[florinc]

Have you tested it using some radioactive material (lie tungsten rods or mantle)?

[TheHomebrewGuru]

Video added

[TheHomebrewGuru]

I don't have any radioactive substances to test it out, but something similar was posted on the CERN website as an educational tool: http://teachers.web.cern.ch/teachers/archiv/hst2000/teaching/expt/new/new.htm

[emcelhannon]

I want to see yours tested on a smoke detector.

[TheHomebrewGuru]

I'm going to ask a friend if I can have his old ones

[TheHomebrewGuru]

Video added

[ricks]

We built this but only see about 200 volts or so when connected to a 3v button cell pack. While we hold the button cell to the leads, the HV output continuously drops.

On an earlier build we thought if 3V gets us 200, then 8v might get use 500 or so, but it seemed to "kill" the unit. Back to the store for a new camera.

Any ideas on what we are doing wrong. We are nowhere close to the 400-600 volts needed to allow the ionization.

[TheHomebrewGuru]

I got 400-600v easy. And do not buy cameras, ask for free used disposable cameras from stores that develop photos. I got hundreds (not to mention free AA batteries). Try a different model camera or make sure that your batteries have enough juice

[atrumblood]

Hmm this looks like a fun project. In the field I work in we deal with compact radiation sources that I could test this on. Something a little more "hot" than an old smoke detector.

[techno guy]

that's pretty cool, i didn't think it would be possible by just putting the contacts close together, but apparently i was wrong

[Caspar]

ps. Am-241 might not have penetrating radiation and may be poisonous. Check the MSDS.

[TheHomebrewGuru]

Opening a slit in the tin might allow the radiation to hit the spark gap

[Caspar]

There are various disposable camera HV supplies, one type uses a neon tube. With a bit of modification, the neon tube (which indicates when the capacitor is fully charged) can be the spark gap. The glass envelope around it makes it rather insensitive, though humidity and vibration effects are eliminated. The neon will strike at around 80-100 V, and some sort of voltage stabilization will improve its performance. Or you could just buy a neon tube, at around 15 to 50 cents.

[TheHomebrewGuru]

I would like to see someone try this, though getting the correct voltage might be a pain. It would eliminate the need for any DIY-er to buy a GM tube off of ebay which would be a first (never been done before). I thought this originally but getting the correct voltage would be difficult. Using multiple neon tubes might increase sensitivity

[spiceyweasel]

It says my breath is radioactive. :(

[TheHomebrewGuru]

Vibrations can make it arc

[AndyGadget]

Do you have to recalibrate depending on the weather?  I'm thinking that high humidity would cause arcing more easily, and therefore the electrodes would have to be further apart.

Thinking on from that, using a variable HV supply and the flash tube from the camera may make a more stable version as the gas is fully contained.  Commercial GM tubes use a variety of noble gases, of which the xenon in the tube is one.

[TheHomebrewGuru]

I thought of using the flash tube initially, and it might work, but you would need a higher hv dc power supply I think

[daemonral]

Hi I was wondering if you could use the flash tube to make it more accurate?

[TheHomebrewGuru]

It would require a higher hv power supply and it would need to be variable because it would need to be calibrated, so possibly, as I've heard that Xenon has been used, but it may be impractical here

[eelco_g]

I always thought that spark gap quenching referred to extinguishing the arc once it had formed between the two conductors. While reading your instructable I wondered if an ordinary neon bulb can be used as a geiger tube? It obviously has an inert gas inside and the two 'electrodes' are close to each other. Has anyone tried this yet?