Cosmic rays are not just photons. A faraday cage is meant to block electromagnetic fields; it won't do anything to stop leptons. In my university labs I rememb

Cosmic rays are not just photons. A faraday cage is meant to block electromagnetic fields; it won't do anything to stop leptons. In my university labs I remember an experiment where we were detecting cosmic ray muons that would travel through a series of stacked lead plates. You didn't have to wait long before recording an event. These particles are big and fast and you need quite a lot of shielding to block them.