Radiation detector, help needed!

98 thoughts on “Radiation detector, help needed!”

1. Hi all.
   Tokyo Hackerspace is working with RDTN.org on the geiger counter and radiation map. They’re a couple of people located locally in Tokyo and one of the guys is coming to the hackerspace meetings. I’m posting my findings on their wiki and will be updating it with the design as it progresses. Here’s my page on the site:

   http://wiki.rdtn.org/index.php/RDTN.org_Wiki:Community_portal/Akiba

   And the main wiki is at http://wiki.rdtn.org .

2. Right now, I’m looking into CCFL flyback transformers. Coilcraft has the FL2810-1L which has a 1:100 turns ratio. I picked up some surplus CCFL inverters locally in Akihabara and will test those out. I also got in 10 of the SBM-20 geiger tubes and will test. I’m going to be asking for a quote from LND on beta/gamma geiger tubes which I think will be less than the LND-712.

   Tokyo Hackerspace will also be assisting RDTN.org and some of the volunteers from the group will be attending hackerspace meetings. They have radiological guys with expertise in the field so it should be interesting.

   I haven’t had too much time to work on the geiger schematic recently since we’re busy on more immediate needs for tsunami survivors. But I should be able to get back on it soon. I’ll keep everyone posted.

3. I built pocket Geiger counters (speaker output – no meter) in the late 60s.

   What I would suggest today is the transformer used in a flash camera – for the “high” voltage. If you need to buy Mouser has a nice selection.

   BTW the regulator on the flash board might work. You would need to “discard” the flash capacitors and replace them with much smaller ones (100 nF @1000 V). Also a trimpot for adjusting voltage.

4. We could actually use a good wikibook on measuring radioactivity.
   And with everything in it you can find.
   Gamma and neutron counters and dosimeters
   All the possible ways to do this.
   There are quit some things possible with PIN photometers, GaAs diodes, ion chambers made from cans with air in and many other things. This is so valuable, I think we really should make a wikibook from stuff like that.

5. Most dosimeters measure if they are exposed to radiation, it is hard to imagine being exposed to radioactive particulates without that happening. So it will come down the the sensitivity of the dosimeter. Most modern ones I have had friends in labs have to use, are sensitive enough that taking one on an airplane will cause it to report exposure when they are reviewed.

6. For those of you that would like to better understand what is currently happening, I recomend this Areva document.

   http://www.seyth.com/ressources/quake/AREVA-Document.pdf

7. does anyone know if a portable dosimeter on your person would work to see if you have been exposed to radiation particulates please respond

8. Can you send a link with your source or more info about the sensors?

   
   admin:
   
   We have sourced GM tube within China, ~
   VN:F [1.9.6_1107]Rating: 0 (from 0 votes)

9. Have you seen this do it yourself device http://www.ki4u.com/free_book/s60p792.htm

10. Sorry, 2nd link should be http://is.gd/66CIkS 🙂

11. I want to emphasize on GM-tubes offered on Ebay those days: PLS do not buy used tubes! GM-tubes have a limited lifetime and do not necessarily stop counting if reaching the end, which makes it difficult to recognize the dead.
    As Okian Warrior wrote, GM-tubes contain two gases (at least). The counting one produces the pulse´s rising edge by avalanching the initial incident by a lot of secondary electrons, the quenching gas stops the avalanche by catching electrons and produces the pulse´s falling edge. As long, as the pulse is up, the tube can´t see any other incident. The nominal pulse length is called the “dead time” (not very clear, should be called “recovery time” IMHO)
    The bad news is, that the quenching gas looses strength by the catching, which prolonges the the dead time if the tube dead is near. In other words: Each GM tube has it´s maximum number of counts depending on the quenching gas (and proper handling, of course).

    Beside prolonged pulses, a good aging indicator is also a temperature correlation in the counting rate. We clamp a KTY10 temperature sensor to the tube, which may be easily linearized and correlated to the count reading by MCUs. In a screening process, counting the same radioactive source at different temperatures identifies bad tubes from beginning.
    Another challenge for MC programmers 😉

    @okian warrior: Thanks for providing info about self-measuring you´ve done. Very interesting.
    I have one caveat: Uwrote: “The russian GM tubes use hydrocarbon quenching, which gets used up over time. After awhile, the tubes will stop working.”
    Although I know some russian types containing hydrocarbon causing lower max counts lifetime, the SBM-20´s data sheet tells it to be halogen(Bromine) -quenched. See here http://is.gd/ZkVQa9 and there http://is.gd/66CIk Lifetime should be no problem (20 billions forecasted) , if one avoids buying used ones. Anyway I agree this tube has a relatively long dead-time (190 µs) and a reduced sensitivity (due to the small volume), but it´s cheap !

12. Japanese crowd sourcing radiation sensor maps and equipment sources
    http://www.rdtn.org/jp

13. just rip one out, its next to the alpha source.

14. Thank you guys for such active response! We have sourced GM tube within China, would post sample photos and carry out experiment ASAP. Cheers~

15. Alex,

    I am interested in getting your thesis. Thanks for being willing to share it. Please send it to “mail” at provideyourown.com.

16. hey
    for calibration (even if , as said , everyone use the same tube ,so only one calibration is needed ) , you can use this :

    http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=260753899259&ssPageName=STRK:MEWNX:IT

    good luck 😉

17. Akiba, I can redraw the schematic and board in Eagle for you. Send me some screen-shots after it is done so that I can produce an exact copy.

    If there are some parts that we have to make footprints for, it will take longer, I hate that part!

18. Here is a circuit based on two 555 timer chips
    published in a German zine in 2006
    http://cc.c.de1.cc/fr/GMcounter06_de.pdf
    A standard (230V) supply transformer drives a HV-cascade, which is degenerated (back-coupled) for stabilization to the timer´s threshold. Keep the 10M resistors clean, as fingerprints may cause drift!
    Although the cascade is designed to provide up to 700V output (some tubes do require this), it requires 250v capacitors and 400V diodes available in stock here. Beside the 555 (you can use a 556 containing two timers), a 75V Zener diode is the only non-standard part.

    @Alex: Pls send a link to your thesis to lab{8}cc.c.de1.cc
    @all: Feel free to ask me, if any German auto-translations remain foggy.

19. Thanks. Gonna check out the DC/DC converter EPE used and see if I can build it.

    Just got a note from the eBay seller for the Geiger tubes and they’re going to take 14-20 days to arrive from Moscow. That’s going to take a while so I’m going to contact LND to pick up 2 LND-712 tubes if they can ship them FedEx.

    One of the Tokyo Hackerspace members is a toxicologist and has access to calibrated radioactive isotopes in the US military research lab. He’s always growing poisonous plants in our backyard. Nice guy, but don’t trust his cooking. We’ll keep people updated on calibration efforts.

    Once we can settle on the power supply for the 500VDC and get in some tubes, then I’ll cut out a PCB on my CNC and put together a prototype. I’m thinking to send it to Shigeru Kobayashi who is working on the data upload to Pachube and visualization if he’s okay with that. Cutting out PCBs is a slow process though so I’ll probably just do one to make sure it works. After that, I’ll send out a batch for fab.

    I’ll keep everyone updated on the status and also schematics. I’ll post the gerbers once things are finalized. I don’t use Eagle so probably someone will need to redraw the files in that tool for everyone else.

    Guess that’s about it. Its going to be kind of a slow process until parts come in, but hopefully we can get something going soon.

20. Sorry, wrong cut and paste; here is the initial publication:
    http://david.alfa-romeo.eu/elektro/EPE/2007/EPE_2007-02.pdf

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