View Full Version : OT: Gamma Spectroscopy

05-21-2012, 05:21 AM
So, A couple weeks ago I found a Harshaw 2"x1.5" NaI(Tl) scintillator attached to a 6199 PMT at a surplus store for $3. Finally got a socket and made up the dynode string and it seems to work well. I am running it off an old Ultravolt power supply.

I decided to give PRA a try, It is a free piece of software that plots voltage height vs occurrence into a histogram that will show you the gamma spectrum of a radioactive source. I ended using my desktop PC which can handle 192khz and 24bit input. I found the settings in the Sound control panel make a huge difference in the amount of noise. 100% volume and +20db amplification gave me virtually zero background noise shown in Intune and there was an audible difference when I monitored through speakers. Intune shows nice clear pulses. The first pic is a capture from my Tek TDS340A of the pulses coming out of the tube.

I need to get a Cs-137 source ordered. Once I get that I can get the thing calibrated to show the electron energy the detector sees. I am really not sure if this thing is working right until I get the source. The problem with the U ore is all the daughters produced with the decay of the U.


http://farm8.staticflickr.com/7057/6994997180_b65e418215_c.jpg (http://www.flickr.com/photos/67292116@N00/6994997180/)
IMG_2238 (http://www.flickr.com/photos/67292116@N00/6994997180/) by macona (http://www.flickr.com/people/67292116@N00/), on Flickr

http://farm6.staticflickr.com/5344/7220403646_138b09a1fc_o.jpg (http://www.flickr.com/photos/67292116@N00/7220403646/)
Scintillator PMT output (http://www.flickr.com/photos/67292116@N00/7220403646/) by macona (http://www.flickr.com/people/67292116@N00/), on Flickr

http://farm8.staticflickr.com/7096/7240311338_931b16446a_c.jpg (http://www.flickr.com/photos/67292116@N00/7240311338/)
Uore2.475 (http://www.flickr.com/photos/67292116@N00/7240311338/) by macona (http://www.flickr.com/people/67292116@N00/), on Flickr

05-21-2012, 09:43 AM
You find some of the coolest junk.:D

Bob Fisher
05-21-2012, 10:43 AM
Trying hard not to flaunt my ignorance, but what will you use it for? I have to agree, though, a neat find, and the price is right.Bob.F.

05-21-2012, 12:54 PM
Somebody bought something for 3 bucks. It's electrical. And Uranium is somehow involved.
How am I doin'?

05-21-2012, 04:19 PM
Yeah, some of the daughters of U decay are real bitches, and all of them are a little heavy for my taste.

05-21-2012, 04:39 PM
and a bitch to machine, even with flood suds

05-21-2012, 07:42 PM
You can use it to figure out what is in stuff. Like last year when fukushima went up I could have seen what isotopes were in the rain water.

Wiki has a bunch on it:


It looks like something I am doing is wrong with my set up. Not sure if I have a bad photomultiplier tube or what.


05-21-2012, 07:50 PM
The only reason you got that for $3 is there's only 2 people on earth that knows what it is, you & the guy that donated it & he probably died of gamma ray poisoning so it all you baby!:eek:

Bob Fisher
05-21-2012, 07:53 PM
AND, after we find what is in the rain water, Then what do we/you do? I don't think I need one. Bob F.

05-21-2012, 09:08 PM
Been a while since I was involved in this stuff but I suspect that a Cs 137 source larger than a smoke detector will require a specific NRC license. Major pain in the ass and red tape.

05-22-2012, 12:15 AM
Nah, they are usually around $50 to $80 depending on amount.