The original simple lead (Pb)? lid worked great as a shield but was giving stray Pb XRF peaks to the detector.
To fine tune it, different combinations of aluminum topped with lead were tried and tested.
It's going to take a thick aluminum lining and a thinner lead top to get rid of the strays.. The picture shows the arrangement of materials that worked.
I discovered that there is leakage along the edges of the thick aluminum when used as a shield, probably from internal scattering. Therefore the final lid will have the aluminum layer a smaller diameter than the Pb top, so it can be completely surrounded by the Pb chamber wall. Perhaps I'll simply attach an thick aluminum disc to the bottom side of the existing lid.
A 10 minute scan to record the background radiation picked up by the Si-PIN when inserted into the chamber, but no exciter present. Only two hits were recorded,? probably random Cosmic Ray Muons
Geo>K0FF
