AN IMPROVED PULSED LOW-ENERGY POSITRON SYSTEM

A pulsed low-energy positron system for positron-lifetime spectroscopy has been up-graded and modified with regard to its three main compone nts. A new moderator preparation chamber has been added, the radiofreq uency pulsing concept has been modified using a pre-buncher and a pre- chopper in front of the existing chopper-buncher section. Furthermore, a new target station allowing measurements at variable temperatures h as been incorporated. The lifetime spectra now reveal a strongly incre ased ratio of peak to background and of peak to satellite peak.