A pulsed positron lifetime beam designed for semiconductor studies is under construction at Helsinki University of Technology [1]. The target of the beam is kept at ground potential to simplify the use of the beam and facilitate sample manipulation while the source and pulsing components are floating. Due to this it is necessary to pay attention to the realization of the high voltage power supply configuration and the HV surge protection. Details of the measurement chamber and the accelerator-decelerator structure are presented.