Josephson junctions as ultrafast nuclear particle detector

The problem of optimizing Josephson junction parameters to realize a fast particle (radiation) discriminator is discussed. The switching operation is investigated, focusing on problems of intrinsic noise and nonequilibrium processes induced by the radiation. The key concept is the effective radiation flux, namely, the flux which produces a number of switchings equal to that produced by intrinsic noise. This quantity gives a direct measure of the device performance. The effects of some relevant junction parameters, such as the junction area, the Josephson current density, and the bath temperature, on the behavior of the effective flux as a function of the response time of the device are presented.