SI-29BG and SBM-20 GM Tube

Never mind!

Good luck with the search and project.

Hello IdeaSmith:

Thanks for greetings. You are welcome.

Shyam, your like a breath of fresh air and humble at that. I subscribed t this thread but haven't had the time to do any research on my own. Between being on call at work and my girlfriend's honey do list keeps me away from the fun things of life, like do something like this. When I do have time there's areas where I go gold prospecting and fishing around Yosemite National Park that has old granite and various other rocks that glow in the dark and always wanted to see just how "hot" these rocks are. Your project would be a cool little instrument to have with me during those rare moments.

Thanks, Dan

Hello dj95401:

Sometime this year I will be in USA to see my daughter who works in Harvard University. I don't mind bringing these instruments to any place in USA and can also let the local group or club to learn to built these. I am always having fun at detecting Cosmic Rays events. It is good to have two systems working at a time for low radioactivity, one for Cosmic Ray background and one for the low radioactivity sample of the rock. Cosmic ray background alters momentarily due to solar flair and other cosmic activity.

Geiger counter have good sensitivity to beta and gamma rays as they multiply ion to 10^4 level to get enough current. Idea is to get the device within $100 such that fun can be cheap but very reliable in performance.

I want many local clubs or groups in USA who make take interest and I can also help University and Colleges.

I will also spend some time in UK and perhaps in Canada. I am retired from Government so I am a free person who makes easy living on Government money for entire life.

Entire sea coast of India is highly radioactive open mine.

Hello dj95401:

Yesterday I did receive CTS-5 GM Tubes 10 numbers from Ukraine based supplier and they look alright to me. GM Tubes were tested for Cosmic Rays monitoring.

I think these CTS-5 GM Tubes are similar to SBM-20 GM Tubes by look.

Now I want to get more GM Tubes from USA, particularly LND 712 and LND 713 types about 50 numbers to involve that many engineering students to try various designs of circuits with these. LND GM Tube are 5 times more expensive.

https://www.youtube.com/watch?v=oGTjp4zMTPA

http://www.ebay.com/itm/like/222007207108?ul_noapp=true&chn=ps&lpid=82

http://www.ebay.com/bhp/geiger-tube

Hello SolarEagle:

Thanks for information. I did order and paid for those 10 numbers GM Tubes US$137 from your last reference but not sure when they will reach me and they may never reach me as they are shipped by post. Other supplier has damaged tubes.

I did get good price from LND Inc. USA now for educational purposes so I am going to order few hundreds from USA LND-712 beta gamma and LND-713 less diameter version types.

I have tested my circuit with LND-712 and with one similar to SBM-20 and entire circuit is responding very well. I initially tried with 15V power supply and then with 6V 4.5AH battery and now 4V 1AH rechargeable battery. It is still working well at low voltages also but I doubt if I can go further down as I am using a MOSFET for the DC-DC conversion which needs 3V plus to fire.

I have to try now with 2V-3V power source also perhaps with lowest gate voltage MOSFET or BJT. I want to avoid BJT to switch high pulsed current of 3A in 10us pulse I am using for 650V MOSFET.

Peak pulse current from high voltage is 16uA to 20uA forming 16V to 20V pulse peak across 1M load resistor and pulse duration is about 100us. I need only 4V to 5V pulse peak so I will decrease the load resistor to about 220 ohms.

I will send design to Electronics Design magazine for publication after it is perfected well.

I will try to get the PCB ROHS such that these can be shared with hobby engineers in all countries.

Here's some other things you might be interested in:

A smart phone can be used as a Geiger Counter if the camera is covered. The camera sensor is sensitive to gamma radiation. There's an app for that.

https://www.youtube.com/watch?v=7y5Kj7vTxgE

Here's an inexpensive gamma ray sensor that fits in the earphone jack of a smart phone. (I haven't tried this.)

Gamma Ray Sensor at Amazon

Hello Rixter:

Yes Radioactive Isotopes are in many common use materials and Radiation sources are not much of a problem for low DPS activity.

I doubt if FTLAB is Geiger at all s Geiger needs high voltage for electron multiplication.

Perhaps FTLAB detector may be an ionization chamber which can work with just 5V bias to collect charge slowly in high radiation zone. There may be Capacitance type ionization chambers used for radiation detection. These work on discharge rate of the capacitance due to radiation caused ions.

I have no idea of their design.