Target Optimisation Studies for Surface Muon Production

The current paper discusses possible designs for a stand alone muon target for MuSR studies of condensed matter science. Considering the ISIS 7 mm graphite target as a reference, Geant4 simulations have been performed in order to optimize the target parameters with respect to muon and pion yield. Previous studies suggested that the muon production can be optimized by using a thin graphite slab target with an incident proton energy significantly lower than initially considered. Surface muon production obtained by firing an 800 MeV proton beam energy onto the target is simulated and potential improvements to the target material, geometry and angle orientation with respect to the incoming proton beam as well as an estimated performance of the muon target are presented in this paper. Implications for the ISIS muon facility are also discussed. A comparison of the pion production cross section between experimental data and three theoretical models for the latest four Geant4 versions is also included in this paper

Geometry Optimization of the ISIS Muon Target

ISIS is the world’s most successful pulsed spallation neutron source that provides beams of neutrons and muons that enable scientists to study the properties of the matter at the atomic level. Restrictions are imposed on the muon target regarding thickness as this will affect the proton transmission to the second neutron target. However, it could be possible to improve the muon production by optimizing the target geometry. Currently the muon target is a 7 mm thick graphite plate oriented at 45 degrees with respect to the proton beam. A set of slices placed at variable distance is proposed instead of the 7 mm thick graphite target. The performance of the set of slices is examined in this pape

Material Studies for the ISIS Muon Target

The ISIS neutron spallation source uses a separate muon target 20 m upstream of the neutron target for MuSR research. Because ISIS is primarily a neutron source, it imposes restrictions upon the muon target, which normally are not present at other muon facilities like PSI or TRIUMF. In particular it is not possible to use thicker targets and higher energy proton drivers because of the loss of neutrons and the increased background at neutron instruments. In this paper we investigate possible material choices for the ISIS muon target for increased muon yield