Making a scintillator

[AnomalySmith]

Hi,

Finally able to (almost) finish the plastic scintillator. For the final version, I used SMD package type resistor which helped me to conceive a low-profil circuit, especially for voltage divider.
I changed the 10MOhm base value with 5.1MOhm following the datasheet's ratio like so:
K-Dy1: 10MOhm
5
5
5
5
5
6
8
11
20
Dy10-P: 15

And it works well.
Just a catch: I noticed the background count rate was bellow the last time I've tested with 10MOhm, I had to increase the sensibility of my Ludlum (Discriminant) to get the same result. But now the whole is disturbed by electromagnetique interferences (like transformer charger, bad-grounded equiment, ...) even though the Mu-metal is grounded around the PMT.
Could this problem be caused by the increasing of resitance value for the last dynodes (even if the global impedance is less than the last time: 120MOhm against now 95MOhm)?

Here is a picture of the beast.

Yvan.

[AnomalySmith]

Hi folks,

I give you some news about this project.
I have lastly decided to improve the shielding of the entire enclosure which helped greatly against interferences. I'm actually obliged to set the sensibility especially for this scintillator on my Ludlum bit it's fine.
The next time, and for those who want to build there own scintillator, I recommend to use metal enclosure which do away with the electromagnetic shielding part (exept of course for the pmt where mu-metal must be used for proper pmt shielding).

Thank you all for your support during this project!

Yvan.

[Sesselmann]

Yvan,

Well done on your project. For EMF shielding of the PMT, you can buy thin sheets of Mu metal on eBay. Mu metal is virtually impermeable to electromagnetic waves.

Steven