High moderation efficiency positron beamline

Abstract A new positron beam system, which has high moderation efficiency and can measure positron lifetime spectra, has been constructed at Wuhan university. A solid neon moderator with about 1% moderation effeciency is used. Secondary electron time‐tagging can be used to measure the positron annihilation lifetime. A target chamber has been designed for positron annihilation lifetime spectroscopy (PALS), Doppler broadening (DB) and coincidence Doppler broadening (CDB). The preliminary beam parameters are: a slow positron flux of 5 million per second for 40 mCi 22Na radioactive isotope, a positron energy spread as narrow as 2.0eV, and a moderator decay rate of 4% per day. Variable energy Doppler broadening annihilation radiation data for stainless steel samples are shown, which demonstrate the capabilities of the system. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)