a little help understanding the issue....

[Marco75]

so..... first tests.
I started with the suggestions from Steven and Tom and playing a little i found one of the main problem is the light!. How much fuc..ng sensible is a PMT?
it is crazy, i had light coming anyway!! Tom you were right, but it seems is not coming from the back but somehow from the front. I put everything below two black thick fabric and something started to change. I am using Am241 and what i see it starts to have a meaning for me. i tested also Cs137 at 32kev
there are still HUNDREDS of calibrations and fine tunings as the spectrum looks TERRIBLE (campared to the same spectrums I can have with GS2020CSI) but at least it starts to make sense!!
tests will continue!

TOM: i hope the weather will improve. Enjoy Firenze ! take care

[Marco75]

okay.... there is still a LOT to improve but first hopefully consistent results are coming:
first picture Am241
second picture Cs137 (xrays at 32kev)
third picture XRF from Cu

[iRad]

Marco - Glad to see you’re making progress. The weather in Venice is perfect, with hardly a cloud in the sky and the temperature around 60°F. Today I feel like a Venetian… Really a perfect day! Ciao.

[Marco75]

Marco - Glad to see you’re making progress. The weather in Venice is perfect, with hardly a cloud in the sky and the temperature around 60°F. Today I feel like a Venetian… Really a perfect day! Ciao.

glad of that!
have fun!
Marco

[Sesselmann]

Marco,

The problem is that NaI doesn't have good resolution in the x-ray region. I have several thin crystals with Be window, but there isn't very much detail in the low end.
I am very keen to do something with low energy, but it probably needs to be CzT or something like that.

Steven

[Marco75]

I totally agree with you Steven. But here LaBr, CeBr or SrI(Eu) are not getting better and in all cases are even worst than NaI for energies below 60kev.
the main problem is the dimension of the NaI crystals that you can get with a beryllium window. we are speaking of a 1-2mm thickness.
this below is the resolution that you can have with a 50mm NaI crystal (with beryllium window) on Am241 energies. 7% on 59kev and lower peaks fully resolved

so the solutiuon exists already . Maybe CzT is a good and very interesting alternatives (i have seen crazy energy res. of 2.5% @662, but don't know the result at very low energy)

my wish is to have something with high res between and 200 kev where you have all the overlaps between different energies.

I am also not sure which could be the improvment considering changing the PMT, for example going from a 9420 to a UBA like a R3998 or the 100 series. i don't know if the resolution would improve

[Madmax]

Hi Marco, Seems unbelieveable.
What's needed to perform same experiment?

[Marco75]

Hi Max,
I am just using data of Scionix on a document provided by them ( a sort of powerpoint presentation) with comparisons at different energies for different type of crystals.
I don't think that I can post here so please write me and I can share
I will be interested in working on a higher resolution solution for xrays in case we find a solution :-)

[Marco75]

new tests are providing better results but i think i an still have better resolution , trying to optimize the optical coupling.
now on Am241 I can see the smaller peak astwo peaks together. the resolution on main line (59.54) is about 20% but potentially i should reach 10-15% in optimal conditions.

[Sesselmann]

Marco,

Interesting how you get better resolution with a larger Be window crystal.

Frankly I long suspected that the crystal suppliers use rejects and broken crystals for the thin 1-2 mm slices, this could explain why they are always so bad. Some customers probably don't care about resolution, so they get away with it.

Steven