You would probably be very surprised about just how much work is put in to characterizing these things. My graduate work was on another experiment (though our postdoc worked on one of the earlier g−2 experiments mentioned here!), but we literally had man-years of work sunk into measuring one thing about the experiment, one number, as accurately as possible and with valid error bars.
That was not the only thing about the apparatus, just one of the most important, but the point is: we cared, we cared a lot, and we cared a lot about a lot of things.
That was not the only thing about the apparatus, just one of the most important, but the point is: we cared, we cared a lot, and we cared a lot about a lot of things.