I don't see the swch problem, maybe you should check your tpt version or disable some mods. I'll make it go down a bit slower for better detection.
maybe also add a second smaller tube, since neutrons go through them easier then photons, photons won't be able to go through the 2nd one so you can technically seperate the 2, anyways just a suggestion i really don't mean to criticize, very sorry
i don't mean to criticize but maybe if it doesn't detect any neutrons for a bit it goes down quicker, and when it detects one, a SWCH turns off for a second or so stopping it from going back down, (again don't mean to criticize, please don't think im rude or im asking for too much, just an idea)
i like geiger counters they're pretty cool
I wish this game had alpha particles/decay as well as other types
the device is not green anymore!