Is There Something Different About the Neutrino Gun?

The way you filter out all particles except neutrinos is that you're relying on the fact that neutrinos really don't interact with much. So when you have the receptor for the neutrinos you're hoping that there's that very small chance that they do actually have that weak force interaction. It seems a little bit like a catch 22 where it's like you are using statistics to try and make your detector see more neutrinos than other types of matter. The key is that nothing else is going to survive so you have this intense beam of neutrinos which mostly ignores the rock but has a few interactions.