Studies of range and straggling of muons in metals by the projected range imaging (PRI) technique

Abstract

A new μSR method for directly imaging the implantation depth distribution of positive muons in metals (Projected Range Imaging: PRI) is presented and the results obtained from several experiments are reported. Strong magnetic field gradients inside a metallic film are produced by driving an electric current in it: spin polarized muons stopped in the film have Larmor precession frequencies proportional to the implantation depth. Generation of field gradients, advantages and features of the method are discussed. For muon energy in the MeV range the results are compared with Monte Carlo simulations and with experimental results obtained by using the conventional moderator curve method. Applications to range and straggling studies with epithermal muons are also envisaged. These future extensions will allow a better understanding of the energy loss mechanisms in the previously inaccessible very low energy range.