Radiation detector, help needed!
We got inquires from Shigeru in Tokyo about Geiger Mueller Tube, as the nuclear accident in FUKUSHIMA is escalating.
Can open hardware community do something to help in this? Seeed Studio is now sourcing sensors, then assemble quick measurement tools, ship as many/fast as possible to Japan.
Since we have no previous experience with such device, your help is needed!
If you have experience in making such device, some quick questions:
1. What would be the right sensor for such detection? Will the education purpose GM tube work?
2. Any recommended peripheral circuits?
3. Does such Geiger counter needs special calibration? Or can we calibrate it with commercial device?
All creations will be open source and donated, thank you for helping out!
About Author
As many have sugested, pin diodes are a good option, they would provide small and portable devices, which consume almost no power.
Check out the “World’s Smallest Geiger Counter” at
http://www.techlib.com/area_50/enricosprojects.htm
john
Unless you are at the site of the event, I’m not sure that detecting alpha and beta radiation is necessary. Those types scatter quickly and are easily blocked. Gamma and x-ray are another story.
Chances are PIN diodes are cheaper than the tubes, but I don’t have a reference price for either.
This is a big business opportunity, Geiger counters are sold out all over Europe for example.
The greatest problem is sourcing a sensitive relatively cheap Geiger tube.
I also started building a counter and bought a Russian SMB-20 tube via Ebay.
Cheers
Rubi
Also, for calibration, you can get sealed radiation sources from United Nuclear:
http://unitednuclear.com/index.php?main_page=index&cPath=2_5
They also carry beta/gamma geiger tubes.
Hi all,
in Libelium we have already started to design a Geiger sensor board to be plugged in Arduino using the cheap SBM-20 tubes.
Once we have the first prototypes we will send to the Tokyo Hackerspace group as Akiba said before so that they can try them and validate them.
This sensor board will be also possible to be plugged in the Waspmote platform (http://www.libelium.com/waspmote) in order to make it work autonomously and wiressly using the ZigBee and GPRS interfaces to send the information when the nodes are deployed in dangerous areas.
comments and suggestions about the coming up design are always welcomed.
David.
Hi. This is Akiba from Tokyo Hackerspace. We have a project going on to setup a geiger counter network. The plan is first to build it around Tokyo and then expand (especially northward) once the sensor feeds are stable. We’re using the SBM-20 geiger tubes which are beta/gamma sensitive and about $18 on eBay.
The tubes that are alpha sensitive are also available. Our quote from LND for the LND-712 alpha/beta/gamma tube was $55 in quants of 100.
Alpha radiation is typically emitted from radioactive decay of heavy elements like Uranium (U-238). Gamma radiation (x-rays) is more typical in fissile by-products which are whats coming out of the reactor. The only worrying thing is that some say that the MOX fuel may release plutonium particles which would emit alpha. Otherwise, we’re going to try using beta/gamma detectors first.
Our plan is to make Arduino shield compatible geiger counters with the SBM-20. We have 10 on the way right now for prototyping.
We can also collaborate on the design going on here and we have members writing software to integrate to Pachube and Geigercrowd.
Nice to see this project going on 🙂
I suspect regular household smoke detectors would provide a suitable and safe calibration source. (not that I have any clue whether they’re readily available in China)
for X-rays, consider this:
http://sales.hamamatsu.com/assets/pdf/catsandguides/high_energy_koth0006e02_3.pdf
I think for your purposes a gamma radiation detector would be enough. Especially is this is in response to the recent disaster in Japan.
http://en.wikipedia.org/wiki/Gamma_ray#Body_response
To measure the level of γ-radiation, consider this chip: http://www.maxim-ic.com/app-notes/index.mvp/id/2236
First of all, thank you very much for your cooperation.
What I have in my mind is upload raw data to Pachube (http://www.pachube.com/) and develop ways to visualize. A few points are already available as: http://www.pachube.com/?q=geiger
I have finished writing code for both Processing and Arduino, and waiting a Gainer Counter (http://www.sparkfun.com/products/9848) from SparkFun.
At current moment, GM tubes are really hard to get (e.g. sold out at SparkFun). Is it possibile to source GM tubes?
You can look at this project…
http://brohogan.blogspot.com/2010/04/geiger-counter-part-2-complete.html
and here is talk about conversion from cpm to Sieverts
http://boards.straightdope.com/sdmb/archive/index.php/t-585737.html
There seem to be number of projects out there which might give you inspiration:
http://www.cyberpcb.com/movie/geigercounter_v1.zip
http://www.best-geiger-counter.com/geiger-counter-kit.html
http://hackedgadgets.com/2010/04/12/diy-geiger-counter-project-based-on-the-arduino-microcontroller/
Hope it helps,
Hans
Wouldn’t something like a dosimeter be more useful and cheaper/easier to produce? Maybe using just some photographic emulsion. It would be a one time use thing, as once it tripped, the detector would need to be replaced.
For this project you don’t really need that much accuracy, just “safe” and “run away” indications. The real problem will be testing such a circuit because you will have to handle radioactive material to do it. I don’t know how easy it is to get in China.
I am actually in Tokyo at the moment. Radiation levels are very low, far too low to cause any harm. The highest amount detected is 1/40th the amount you receive when getting a medical x-ray, and I have had 16 x-rays in my lifetime.
I am a chemist and although I would normally welcome any device that can measure something (it’s in the genes), I would strongly advise against building these devices on your own. Most of the cheap devices you can buy can have huge errors, leading to panic if the reading is higher than it should be or to ignorance to danger if the reading is too low. In any case you would also need a radioactive source so you can calibrate it for the higher readings, which is something you should NOT do without precautions. Just my two cents.
http://www.sparkfun.com/tutorials/132
this one g8
Addendum:
The russian geiger-muller tubes referred to by skater_j10 (http://shop.ebay.com/i.html?_nkw=sbm-20+geiger) seem pretty good to tell you quickly whether you are in any immediate danger. Accurately measuring radiation levels near background can take some time though.
If you take a background radiation of about 0.3 uSv/hr (approximate of the UN 2000 estimate) and the sensitivity mentioned you expect about 0.6 counts per second. If you are only concerned about quantization error and you want to get roundabout 5% accuracy, you would have to measure for 20 counts, or about 33 seconds.
This is without any enclosure. Covering the tube will limit the sensitivity further, especially for alpha and beta radiation. The tube operates at 400V, so an enclosure might be a good idea nonetheless …
I’m a physicist, but my knowledge of kit GM counters is severely out of date. I built one in the aftermath of the last serious nuclear accident — about 25 years ago now.
I remember it was a bit of a fiddly project.
The tube required high voltage to operate. It was produced using a charge pump-like system to get hundreds of volts out of a battery. That means that you need to take lots of precautions to avoid shocking the operator and damaging other components.
Also, the tube itself was very fragile, with a thin mica window to collect the less penetrative radiation types. The enclosure was a bit of a balancing act between protecting the tube, keeping the high voltage away from the operator and interfering with the measurement as little as possible.
If your tube is not very sensitive, you will need longish measuring times to detect normal levels of radiation. My kit had integration times of up to 30 seconds. With a modern microcontroller based design that does not have to be a problem, as you can easily keep a moving average.
Calibration is an issue. On average your instrument will pick up X% of all event. Calibrating the instrument means figuring out how big X is and compensating for it. Unfortunately, X depends on the physical construction of the device and the enclosure, and it’s fairly tricky to estimate from first principles. Eventually I resorted to reference samples (for beta and gamma) for calibration.
Here’s a better explaination of the Detector theory: http://bit.ly/gTrTup
I forgot that when radiation is detected by a GM tube pulses are emitted which gives you the audible clicks and pops. For the Sodium Iodide crystals photons are emitted that are picked up and outputed to op-amp circuitry by a Photo Multiplier Tube (PMT) (which needs High voltage to run as well).
As long as you have a tube (helium filled or other inert gas) or Sodium Crystal (coupled with a PM tube) that can detect radioactive particles (Alpha, Beta, and/or Gamma), such as ones from Electronic Goldmine, you can then use a high voltage circuit to excite the gas molecules inside in order to collide with the radioactive particles which will emit energy. The energy will then effect the high voltage signal and then you’ll need to feed that to a step-down circuit that’s further fed to a speaker (piezo) and LED for your output. Electronic Goldmine has posted a circuit diagram to use these tubes here: http://bit.ly/h6xf9m (So the description may not be perfect but I was employed as a Nuclear Energy Worker (NEW) for 5 years so I know a little theory)