my fukushima soil spectrum

[Peter-1]

Hi all,
here is my spectrum from the soil.

2017_08_15-Cs137-J.png

its very interesting for me. Thank you to Luuk.
Peter

[luuk]

Hi Peter,
That is a very nice spectrum what detector did you use to get it this good?
Luuk

[Peter-1]

Hi Luuk,
take a look by detectors and "my system". The PMT is from EMI 9656B.

Peter

[luuk]

Hi Peter,


Yes I looked at your setup but I think that your resolution(5.6%) is to good to be true for a NaI(Tl) is in my eyes nearly impossible.
I an a suspicion guy and when I see resolutions for NaI(Tl) from below 6% @ 662KeV there must be something wrong.
Best I have ever seen is 5.8% with an standard NaI(Tl) and trust me I have seen and tested many detectors over the years.
I did some test with a very special pmt and then 5.5% @ 662KeV was the best I could get, problem is that only this pmt cost already 650€.
But on the other hand I must also say that your spectrum does not seems to be none linear, I don’t under stand how you get this extreme good results.
But a great result for sure!

Luuk

[sgt_bear]

Like luuk said, 5.6% for a NaI(Ti) is nearly impossible, especially with sound-card spectrometry.

Don't be fooled by theremino. Theremino is a quite qood software since it has a nice GUI and a isotope selector. But it has two main disadvantages:

"Equalizers for Energies" - they can be used to get the energy scale linear, but when you use the slider, your peaks are getting more wide /narrow and give you a false looking height. I was once fooled by this

"Resolution Compensation" - According to the manual of theremino, this can be used to make the peaks more clear by compensating the resolution - but there is no formula or anything how to set them up. So the feature is pretty usefull.


I wish that the "PRA" makers implement a isotope selector one day...

[Peter-1]

Hello,
I do not want to spread fake news. Yes I have the filtering of Theremino used to see the line at CS134 better. In order to show what my system can i show the pulses from minimum to maximum.

Puls-min.jpg

Puls-max.jpg

A new diagram without filter is here.

2017_08_20-Fukushima-3.png

I hope it will bring a little more clarity.

Peter

[luuk]

Jonathan,
Thanks for the explanation, I have no experience with this software, but that is just cheating :-)

Peter,
7.5% that is more realistic, I was wondering if you might found the perfect crystal :-)

Luuk

[sgt_bear]

Luuk, it only would be cheating if the user knows and uses it to say he has a better resolution. :)

In the beginning i didnt noticed it either, and was worried by to small resolutions (in my case)


Personally i use the equalizers, but i dont care about the resolution, the spectra is more important, and to have the peaks at the right place i have to use the equalizers to get the scale linear.

I guess PRA software does something similar since you can have more than 1 calibration point.

[Sesselmann]

Jonathan,

Marek suggests using linear interpolation in PRA, this basically creates a linear calibration between calibration points. In reality the non linearity seems to originate from the PMT or divider and it generally follows a quadratic polynomial function.

You can calculate the best fit polynomial function in Excel and insert this function in Becqmoni which is the only gamma spec software currently with this function.

Steven