Gamma Spectrometry Forum

Hi Guys,

I just happened to have two identical detectors on my desk today, so I decided to do a coincidence spectrum with My Na22 source.

For comparison I also did another run with a thorium mantle.

Results are as expected, but I thought it might be interesting to plot it as a scattergram after I saw one of my clients do this.

Steven
The pure coincidence spectrum of Na22 produces a beautiful sharp peak, as the other incident gammas are nicely suppressed.
The scattergram, showing clear lines at 511 keV and 1022 keV (2 x 511)
The coincidence spectrum of Thorium showing no such clear patterns of coincidences.

Hi Steven,

coincidence data contains so much more information than the normal spectrum. I recently got my own setup running 2 old 3x3 NaI with self made PMT bases. Because PRA software doesn't support 2D coincidence histograms directly, I had to write my own simple sound card acquisition software. I use GNUplot for visualization of the data.

below is a Thorium mantle 2D histogram (number of counts is color encoded on a logarithmic scale) after approx. 8h.
Axis are not calibrated and my setup is a bit non-linear towards the higher energies. But I'm pleased with the results so far.
It would be cool if programs such as PRA would support this directly.

Michael

Michael,

That's pretty cool, maybe it can also be represented as a 3D plot.

Steven

Steven,

Steven Sesselmann wrote: That's pretty cool, maybe it can also be represented as a 3D plot.

Yes, it can be done for example with the ROOT toolkit from CERN https://root.cern.ch/. The result looks quite nice and illustrates even better the gain in information compared to a single detector measurement.
Another nice side effect of coincidence spectroscopy is the reduction of background, even without shielding, because it is very unlikely to have a coincidence of gamma-rays from the sample and from the background sources.

I want to try if it is possible to identify some isotopes in the Thorium decay chain with such a measurement.

Michael

Michael,

That's very neat, very interesting also thanks for sharing the link to the software page.
Steven

Hi I m measuring same spectra but with 2x HpGe detector and ADC is PCI-9820 (14bit 20MSps) Na22. Its normally used for Coincidence Doppler broadening spectra of the anihilation energy peak. If precise 511keV is made then you will see something similar like in attached pictures.

Offtopic: I see "Merania" in the winodow's title as folder. Slovak ?

MartinM wrote:Offtopic: I see "Merania" in the winodow's title as folder. Slovak ?

Ano