Sciencemadness Discussion Board - DIY Gamma Spectrometer with MCA

DIY Gamma Spectrometer with MCA

Alexey-RH - 28-4-2018 at 00:34

Hi,
I want to share photos of the project I recently finished. My gamma ray spectrometer project has 2 parts: detector and MCA module. The detector can be also used independently with computer software like PRA.

I started with making the detector that has NaI(Tl) crystal 30x40mm and R9420 tube. High voltage step-up and pulse amplifier are installed on tube. The enclosure has additional board with lipo battery and charger (not shown on the photos)

On the detector output I have ready PMT pulses, one of the typical pulse are shown in the attachments photos.

typical_PMT_pulse_shape_from_amplifier.jpg - 75kB

Alexey-RH - 28-4-2018 at 00:40

Next step was to make electronics adjustments to find optimal mode for the tube for best FWHM% and linearity. I use BecqMonitor2011 for the tests, the software based on PRA sourcefiles.
The adjustments ended up with ~7.30% FWHM% on 662keV
On computer I use 24bit Asus audio cart for that purpose.

R9420-800V-900K-boxed-cs-137.jpg - 399kB

Alexey-RH - 28-4-2018 at 00:47

The portable multi-channel analyzer is also my DIY project. I purchased MHH-95A enclosure and prepared PCB design of the MCA that can fit this box.
The MCA module build with PIC18 8-bit processor and it has 10bit ADC 1024 channels. The 128x64 display can show only partial information of spectra, the full 1024 bins CSV is saved to SD cart.

Alexey-RH - 28-4-2018 at 00:53

The finished project photos below. The detector turn on automatically when cable is connected. The lipo battery inside the detector charged through same cable and 5V adapter.
The MCA is powered with 2xAA batteries.

Alexey-RH - 28-4-2018 at 00:58

The CSV files as recorded by PIC18 MCA.
1. Cs-137 1 hour log.scale
2. Radium old watch 30 minutes linear scale
3. same Radium old watch 30 minutes log. scale
4. Thoriated lantern mantle 30 minutes log.scale

Ubya - 28-4-2018 at 05:40

really nice work!
it looks (and i'm sure it is) really professional and well made.
may i ask what's the total price of the project?

Alexey-RH - 28-4-2018 at 06:14

Thank you for the feedback.
The project is NOT cheap. I don't have exact cost summary for every part I used in this project, but the most expensive are:

1. NaI(Tl) crystal. I purchased this sample new for about $200. It expensive mostly because it has guaranteed resolution and it manufactured in nowadays. Old stock crystals are problematic in my experience.

2. R9420 Photomultiplier Tube. $60 The PMT tube I used is not new, but in good condition from trusted supplier.

3. Enclosure manufacturing. Even I do it by myself it has cost and need a lot of time. The materials in small quantity I buy are expensive, for example tube, aluminum rod and plastic can cost you about $100 including shipping, you also need to add machining costs on tools, inserts etc.

4. Electronics prototyping and PCB manufacturing. The cost is high. I even cannot count the total hours, days and months I spent on this subject. I addition I try to avoid low cost ebay-ali electronic components. The MCA microprocessor software wrote by me too. It took for me too many resources and time, as a self-employed maker and student I choose not to share my source files because it will never cover my costs indeed, sorry.

5. All other parts around like cables, jacks, batteries, materials, glues, tapes and etc are about $100, yes small things makes difference here...

[Edited on 28-4-2018 by Alexey-RH]

[Edited on 28-4-2018 by Alexey-RH]

pantone159 - 28-4-2018 at 08:32

Wow, that is very impressive work. I want such an instrument someday, but I would never make it all myself.

What radionuclides do you think you can detect from the Ra and Th items?

Alexey-RH - 28-4-2018 at 09:23

The calibration low activity isotopes samples I have where purchased from spectrum techniques. Some low radioactive items are from ebay, like a Chinese "scalar energy" pendant what contains Th-232. I did gamma spectrum of Cs-137, Co-60, Am-241, Th-232, Ra-226, Lu-176, Ba-133, Eu-152, Tc-99m, natural background with K-40 and radon daughters, I also have in collection fiestaware plate with uranium glaze.
Of course I cannot get short half life isotopes that produced by neutron activation, but if the gamma is in range of 20keV-3000keV it will be detectable for sure.

Alexey-RH - 28-4-2018 at 11:06

Eu-152 + Cs-137 gamma spectrum

R9420-800V-900K-eu-152-cs-137.jpg - 235kB

neptunium - 5-6-2018 at 17:59

very nice work indeed! very happy to see others interested in gamma spectroscopy!

https://www.youtube.com/watch?v=5l9wAgXETR4

and maybe

https://www.youtube.com/watch?v=b83ekaPKr1w&t=15s

https://www.youtube.com/watch?v=7J2CEuuXQoU

and if you haven't already may i suggest...

http://www.sciencemadness.org/talk/viewthread.php?tid=27963&...

[Edited on 6-6-2018 by neptunium]

stamasd - 16-6-2018 at 05:50

Nice work. I believe I have purchased from you in the past some of the older Geiger counter kits you were selling. I see that you're working on getting some PIN diode detectors working also http://www.rhelectronics.net/store/gamma-photon-nuclear-radi...

I've made some detectors myself, with various NaI(Tl) crystals and PMT tubes purchased probably from the same source you have. They work well for their size with a Theremino-style adapter, though making enclosures for them was a pain since I don't have much available in terms of metalworking equipment and had to improvise. I've also played a bit with LYSO (lutetium yttrium oxyorthosilicate) as a detector, not much success due to the high intrinsic background of these crystals from the 176Lu isotope...

Alexey-RH - 17-6-2018 at 12:42

neptunium, subscribed to your channel now

stamasd, I have SiPM with CsI, it gave much more greater results than PIN diode alone. SiPM with CsI can be used for counting and counting application has simple circuit because SiPM needs only 30V bias comparing with PMT that needs 1KV. But I'm experimenting with SiPM in gamma spectroscopy field. My result until now was 7% FWHM.

stamasd - 17-6-2018 at 16:55

I don't have any SiPM. Been looking around on ebay and other places for about 9 months now. I envy you.

MJ101 - 17-6-2018 at 17:10

It's beautiful.

Best of luck with everything.

Alexey-RH - 18-6-2018 at 00:11

Quote: Originally posted by stamasd

I don't have any SiPM. Been looking around on ebay and other places for about 9 months now. I envy you.

https://sensl.com/estore/microfc-60035-smt/

you can order SiPM from manufacturer

new crystals from manufacturer; they can cut size you need:
http://www.epic-scintillator.com/CsI-crystal-scintillator

Quote: Originally posted by MJ101

It's beautiful.

Best of luck with everything.

Thank you.

[Edited on 18-6-2018 by Alexey-RH]

[Edited on 18-6-2018 by Alexey-RH]

stamasd - 18-6-2018 at 02:18

Quote: Originally posted by Alexey-RH

https://sensl.com/estore/microfc-60035-smt/

you can order SiPM from manufacturer

Oooh that's very interesting. The main page says they have been acquired by On Semiconductor. I have had an account with OnSemi for many years and can get free samples of many products. Recently I've been sampling many Fairchild high speed MOSFETs (they bought Fairchild too not long ago). I don't see SiPMs listed on their product lineup yet. Who knows, maybe soon. Though they usually don't offer free samples of parts that cost more than $10 per piece or so.

[Edited on 18-6-2018 by stamasd]

neptunium - 19-6-2018 at 10:34

Quote: Originally posted by Alexey-RH

neptunium, subscribed to your channel now

Sweet! thanks ! here is a link on how to lower the FWHM with NaI(Tl) but 7% is already pretty good ...

http://pico.dreamhosters.com/soft/MinimizingFWHM_ENG.pdf

Alexey-RH - 21-6-2018 at 09:42

Just have to say, before start to check resolution, I would recommend to check linearity or detector and amplifier first on low and high energies. Hobby devices, like Theremino and DIY probes usually are non linear on higher energies. A solution for second order polynomial equation can fix nonlinearity in narrow region in MCA software, but if the system has large nonlinearity factor then resolution will degrade after energy calibration applied. For example in BecqMonitor2011 for Energy[keV] = ax^2 + bx + c (x = Channel Number) solution, the nonlinearity factor "a" need to be a<=0,00005 Look at my screenshots above with software settings of energy calibration.

http://www.sciencemadness.org/talk/files.php?pid=515861&aid=67770

If you plot that function in range of 0-1024 channels then the energy results will be almost ideally linear for range of 0-3000kev.
I found it tricky to get perfect linearity of the hobby DIY hardware, but at least the range I need up to 3MeV is linear.

[Edited on 21-6-2018 by Alexey-RH]

Alexey-RH - 21-6-2018 at 09:47

I use Eu-152 +Cs-137 to find channel number for 122kev, 662kev and 1408kev and after that make energy calibration.

Alexey-RH - 21-6-2018 at 11:43

Gamma spectroscopy SiPM CsI(Tl) detector that works with audio cart and amateur MCA software. It run with one 9V battery and turn-on automatically when I plug the cable. Battery mA drawn ~15mA. The electronics in prototype stage, made on home-etched PCB.

The pulse amplifier has some non-linearity issue, I hope it will be resolved later.

Alexey-RH - 20-7-2018 at 10:29

Prototype of gamma spectrometer with builtin USB interface. The computer connect to the device as to an external USB audio card. Works nicely with Theremino and BecqMoni.

stamasd - 20-2-2019 at 09:12

Just a quick update on the SiPM, I was recently able to acquire one through OnSemi. Wasn't cheap, $100 for a 6x6mm detector. Haven't had time to play with it yet. I plan to try a 5x5x 20mm LYSO crystal with it.

[Edited on 20-2-2019 by stamasd]

Alexey-RH - 3-5-2019 at 06:04

Yes, the 6x6mm SiPM cost about $100. New CsI crystal with sizes 10x10x50 is also about $100
The toy is not cheap and small

Alexey-RH - 26-7-2019 at 14:09

assembled prototype with CsI(Tl) + SiPM. Temperature compensated circuit for range 5C-50C. MCA 1024 bins.

Alexey-RH - 26-7-2019 at 14:12

Fluorine-18 from CT PET, 511keV is visible.
Activity seems to be nicely high, here on the photo about 2 meters away from a patient after PET and instrument reads as ~1500 CPS

Alexey-RH - 26-7-2019 at 14:17

Tc-99m spectrum, 140keV + 75keV from lead container
Spectrum recorded at about 1000 CPS count rate from a distance, I don't remember activity of the source but I was told it in range of several mBq

Alexey-RH - 14-2-2023 at 07:21

Project updates: I wrote RIID software for the following isotopes:
Cs-137, Ra-226, Th-232, Bi-214, Ba-133, Am-241, Lu-177, Eu-152, K-40, Co-60, U-235, I-131, Co-57

here is the short video:
https://www.youtube.com/watch?v=HJWBur8yqVU

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