Generation of very slow polarized muons by moderation

At the Paul Scherrer Institute very slow, nearly 100% polarized, positive muons with an energy of ∼ 10 eV are produced by moderating a secondary beam of surface muons in a thin film of an appropriate condensed gases. These epithermal muons can be used as a source of a tertiary beam of tunable energy between ∼ 10 eV and ∼ 20 keV. Such a beam allows the μSR technique to be extended to the study of thin films and surfaces.In order to be able to perform time differential μSR experiments we have developed an ultra-thin detector that registers the passage of keV muons and permits to trigger the experiment. The results achieved so far demonstrate that first investigations of thin film samples can be performed with the present set-up