Snow shielding by muons?
Another once-asked-question (OAQ) about the exposure age calculators [names and places anonymized…]:
Dear Greg: I am working with some CRN data from the [Misty] Mountains in [Middle-Earth], and have a question regarding the use of shielding factors in the CRONUS calculator. We believe that snow shielding may be an important factor in this relatively high elevation area (~1000 m asl), and wish to do some simulations of the effect of different snow depths. My first thought had been to do this via the shielding factor, but I note from your paper of 2008 that this factor is only applied to the spallogenic production rate, and not the production rate due to muons. Before I start modifying the Matlab code, I wanted to ask if you had any thoughts or recommendations. Perhaps work has already been done on this issue, and it would be useful to know of any potential pitfalls.
Dear [Frodo]:Yes, the shielding factor is not applied to production by muons. However, i) at elevations much above sea level, production by muons is very small relative to spallogenic production, and ii) the fall-off of muon production with depth is an order of magnitude slower than for spallation. Say, for example, that you have snow shielding in the amount of 10% of spallogenic production. This will only have about a 1% effect on production by muons. Production by muons is about 2% of surface production at 1000 m. Thus, the inaccuracy created by ignoring muon shielding in this case is 1% of 2%, which is obviously very much smaller than the uncertainty in your snow cover correction and is insignificant for your purposes. In fact, this is nearly three orders of magnitude smaller than the production rate uncertainty. The summary is, you can just enter the snow correction you think appropriate and not worry about it further. I strongly suggest instead spending your time looking for good production rate calibration sites…regards,–greg