Cool stuff! Here are a few interesting resources:

http://www.techlib.com/science/ion.html - old and gold. A friend tried building these ion chambers, but apparently getting high enough isolation between the container and the electrode was very hard.

http://physicsopenlab.org/2016/04/24/diy-cherenkov-detector/ - one for detecting muons (a PMT taped inside a thermos)

And a fun little application note from Maxim to build a gamma detector from a photodiode : https://www.maximintegrated.com/en/design/technical-document...