putting together a gamma spectrometer (using soft MCA)

Hello, it's been awhile since I've posted on here but I though I'd let you guys know what I've been up to.

I getting back into building things now that I've found once decently active test source. I've got a 160uCi Am241 "test" source that I'll use for now to detect the 3 distinct photopeaks.

I have on order a BCM408 organic Scintillation probe for gross incident counting from iRadlabs. Though the resolution sucks for spectroscopy, I intend to use use this on my LENI-CDV700 for going Uranium hunting in a HOT area of B.C. known for Uraninite, gummite and Uranophane. (it might need a pre-amp to amp the incoming signal on the CDV700) I'm going to use this to test the HV power supply and CPM on the Gamma spectrometer once it's up and running.
BCM408 produces a very fast 2ns pulse which is a challenge to pick up with most standard signal processors. ( Why it sucks for gamma spectroscopy but ok for gross counting)

My project that I'm trying to get underway relies on a Quadcore ARM board called an Odroid XU3. It's quite capable of handling highspeed data and complex video/3D processing. The spectrometer part relies on a SoftMCA
(either Theremino MCA, PRA or BecqMoni MCA) and an Audio ADC capable of at least 96Khz 24bit resolution.

HV will be supplied by a Gamma spectacular HS2000 pro spectroscopy driver
and a large Li-ion pack that will power both the Odroid XU3 and the HV unit.

( I scrapped the idea of the GCE project as the ADC is only 10bit and there have been huge issues with read/write i/o on the card slot). Most cards now are diff voltage.

My biggest hangup is on the software. Since I am going to be running linux
(Unbuntu 14.04) on the board I need to be able to run the software natively. I had thought of using WINE on the board but having already tried it on a computer I found the performance very poor esp. on Theremino MCA.

IF anyone has an idea about translating Theremino MCA for use on Unbuntu or other SoftMCA for use in this handheld Gamma spectrometer project please let me know!

Thanks.


I've attached pics showing my LENI-CDV700 doing a distance test with a few of my sources.. the box attached to the meter is a homebuilt high precision scaler to do calibration of the meter or do accurate CPM/or CPS.
If you want to build the scaler PM and I'll get you the parts list. :angel:

Last pic is showing what happens to a covered webcam being exposed to the gamma photons from the 120uCi Am241 source. Webcam has a piece of ZnS/Ag image intensifier screen under the cap than acts to capture the incidents. The dots are Gamma rays interacting with both the scintillation layer
and the CCD sensor. the large flashes are from the 59.5KeV photons and the smaller background dots from the 2 lower energy photons 26.3KeV and 13.9KeV (X-rays)

Here is the new Scintillation probe from iRad labs on my LENI-CDV700.

Indeed, I'm going to add a preamplifier to the counter as the pulses are far to weak to be seen my the internal circuitry.

I'm getting pulses 1 or 2x every 4-6seconds seconds background and about 7-10cpm on a very hot uraninite specimen.

luckily there is a new preamp circuit that looks fairly simple to build for the LENI-CDV700.

Note the pic on the far right is modded in the .pdf. (new amp is the GEO 01 JP01) ----> have a look.
The new circuit is just the upper part of the amplifier circuit on the far right image.

If anyone has a program that could build a circuit board layout I'd be forever grateful
I plan on either building one or purchasing one.



The MCA project is a competely different item. This is just me getting used to scintillation probes. The CDV700 circuit produces FAR
too much noise to be used as the HV for an MCA but will suffice for use a gross gamma scintillation counter for going hot-rockin.

Seoul_lasers, I found your new project interesting. I was under the impression that uranium hunting was a lost project as back in the 1950s people were thinking of getting rich by finding new sources of uranium ore. But, in the intervening years it has lost favor as there hasn't seemed to be a market for new sources of ore. Has this changed? Or is this a Canada thing, where Canada is looking for new sources of ore?

paul1598419 said:

Seoul_lasers, I found your new project interesting. I was under the impression that uranium hunting was a lost project as back in the 1950s people were thinking of getting rich by finding new sources of uranium ore. But, in the intervening years it has lost favor as there hasn't seemed to be a market for new sources of ore. Has this changed? Or is this a Canada thing, where Canada is looking for new sources of ore?

Click to expand...

haha, no we have some huge uranium mines in Canada, primarily in Far Northern Saskatchewan and Northern Ontario. We too like Washington State have very large Uranium deposits in the interior, only there is a moratorium on mining it. Spokane had 2 or 3 open pit mines in the 30-40's and 50's for producing weapons grade uranium as well as for power. Much of the same deposit also exists on the Canadian side of the border some 300-800ft blow the surface around peachland , Summerland and Osyoos.

We seem intent on only doing oil in "full scale" in Canada and that's going to be our downfall. We need Uranium additionally to keep our energy resources varied.

Gamma spectroscopy has caught me eye because of the recent softMCAs becoming available for phones, tablets and computers. Some excellent work from both Australia (Bee research) Gamma spectacular and Theremino MCA based out of Italy. Theremino's soft MCA works extremely well
as a sound card MCA utility. Even more interesting is it's ability to be used in XRF. :beer:


The posted file .png is of a Cs137 1uCi source on a 1.5" NaI/Tl detector. This was an audio recording played though Theremino MCA. The pulses were binned properly and the resulting spectrum even shows the 32KeV Xray emission. This took approximately 30seconds to show up at 192Kz sampling rate at 24bit depth. :yh:

Hmm, very cool! I hadn't heard about the iRad labs yet, I'll have to look into it.

Look forward to seeing the progress on your mca project!

How about some more pics of that am source?

Sigurthr said:

Hmm, very cool! I hadn't heard about the iRad labs yet, I'll have to look into it.

Look forward to seeing the progress on your mca project!

How about some more pics of that am source?

Click to expand...

The process on the MCA will be fairly slow. Due in part by lack of funds. Spring break.
I'll get some close up pics of the source (s) once I get my camera battery charged up again. It's actually 2 core ionization sources @ 60uCi ea.
The amount of active material is 160uCi total in the chambers.

Again, all will be used for Gamma spectroscopy and particle interactions.
:san:

Pic of the same source below. 60uCi for the source below.

That is a very interesting source!

Sigurthr said:

That is a very interesting source!

Click to expand...

Next will be to acquire a Cs137 source @ about 5-10uCi.
This will be the Calibration source for the meter. Unfortunately I think that such a source here in Canada requires a massive amount of paperwork to import and CNSC transfer papers (~$400CDN).

If you know of a good "fresh" Cs137 source several uCi let me know, I'll need it once I get everything built.


In Fukushima pref and Ukraine it's free. :wave:

SL, I was thinking about your spectrometer and, though I'm not up on the technology, gamma radiation is ultra high frequency photons that, unlike X- rays, can't be refracted by the atomic structure of crystals. I'm wondering how you are going to get the frequency of the gamma radiation as I understand it this can only be done by very circuitous means.

Hey Paul,
In most scintillator materials there is a correspondence between pulse intensity and wavelength, as such in the PMTs used there is a correlation between pulse height and detected wavelength. By sorting counted pulses by pulse characteristics they're able to generate a graphical picture of the gamma source. Wish I could explain further, but the cost of scint probes has prohibited me from engaging in their use and finer points.

paul1598419 said:

SL, I was thinking about your spectrometer and, though I'm not up on the technology, gamma radiation is ultra high frequency photons that, unlike X- rays, can't be refracted by the atomic structure of crystals. I'm wondering how you are going to get the frequency of the gamma radiation as I understand it this can only be done by very circuitous means.

Click to expand...

Thanks, Sig. This gives me a direction to look for the answer to my question.


Already knew about the correlation of gamma photon energy and wavelength. I thought I was going to find some technology that made making this correlation simple and give a direct way of determining wavelength, but so far, nothing I didn't already know. Maybe you could give me a link that would show me something new, Sig.

I think you misread what I wrote and missed out on the explanation; the gamma energy determines the pulse height electrically of the pulse generated in the scint probe.

Anyway, see: https://www.google.com/url?sa=t&rct...TuMPBjKZA7yjOOqVfLU8Yw&bvm=bv.110151844,d.eWE

Excerpt: "Because the amount of light (number of photons) produced in the scintillation crystal is proportional to the amount of gamma ray energy initially absorbed in the crystal, so also are the number of photoelectrons from the cathode, the final anode charge, and the amplitude of the preamp and amplifier voltage pulses. The overall effect is that the final pulse height is proportional to the gamma ray energy absorbed in crystal."

Been away for the past few days and didn't get to look at the information provided. It seems like what is really new in this detection system is the software involved in doing some of the tedious calculations and manipulating them so one gets a useful output of the spectrum from the radiation source decay. Would love to get a chance to observe one in action.

Hi there, I have been away for quite some time. Mainly because of a college electronics course and CompTIA A+ certification.

I am starting a completely different course next week.

Yes, I got a new probe kit coming from USA and Russia. I have a CsI/Na crystal on the way with a high quality PMT kit from Irad labs in Florida.

more pics on the way.

SL, I'm looking forward to seeing what you come up with.

This stuff both terrifies me, and fascinates me ...its like the forbidden fruit, using radioactive material.