A method for evaluating the transmission properties of ultracold-neutron guides

Abstract

A method for evaluating the properties of guides for ultracold neutrons (previous termUCN)next term has been developed as an extension of the common technique for measuring previous termUCNnext term losses in the sample contained between two diaphragms. With two measurements at both ends of the guide one can evaluate both, the loss probability _s13_s17956_s19 per wall collision and the probability f for diffuse scattering from the wall. A 3.4 m long aluminum tube coated with a double layer of stainless steel (thickness 500 nm) and beryllium (thickness 250 nm), proposed as a previous termUCNnext term guide for the Mini-D2 previous termUCNnext term source at the FRM-II reactor at Garching, was tested. We obtained _s13_s17956_s19=(1.1±0.1)×10-3 and f=0.18±0.04. Systematic errors and a possible improvement of the method are discussed.