We now need to see how often a muon of sufficient energy to produce a significant noise pulse will pass through the detector and then determine how often such a muon will interact close to the detector and actually deposit energy. Also, at a fixed primary energy, the cosmic ray nuclei have a mixed composition and, if we are concentrating on high energy muons, we are only interested in the proton primary component. This is because other, more complex, nuclei will produce more, but lower energy, muons. If we take shower primaries with an energy of 1TeV, we can say that the flux of muons produced with energies above 0.2TeV is about per square metre per year. As we noted earlier, an energy deposition of this order is capable of producing significant noise in presently proposed antennas.
Muons generally lose energy by ionisation.
We need to consider the probability of such an event occurring in the gravitational detector for a muon of this energy noting that already, by selecting these energetic muons, we are examining only one muon in 30,000. If the gravitational detector has an absorption thickness of 10 to 100gcm we would thus estimate that there is a probability of about one in of our muon interacting in this way in the detector. We are now looking at about 1000 potential events per year per square metre. The question now is how much energy will actually be deposited in the gravitational detector. The detector will absorb some of the energy but, with a limited thickness and typical ionisation loss rates of charged secondaries of 2MeV per gcm or a few hundred MeV per particle per detector thickness, a significant fraction will leak out.