Comparison between two positron annihilation setups

After the design, the building and the installation of two new setups for positron annihilation at RMO/SCK.CEN, including their radiological shielding, it was necessary to establish a procedure for the calibration, and optimization of the techniques before measuring the irradiated material. Up to now, the work has been devoted mainly to measurements on non-radioactive specimens including very pure and well annealed metals and alloys. Measurements on radioactive specimen necessitate a very good knowledge of the electronics, the acquisition systems and also the calibration methodology. To gain some relevant experiences on the methodology of performing correct measurements, one of the authors (MJ) has spend few weeks stay at the well experienced and world known lab of Prof. Hasegawa at IMR /Oarai branch. During this visit, aspects like calibration, specimen preparation and mounting, data acquisition and analysis were carried out using the very same samples. In this report, the technical description, the measurement methodologies as well as the results obtained in the two setups are compared. It is demonstrated that an updating of the RMO/lifetime setup by using a high speed oscilloscope instead of the fast-fast coincidence setup will allow a much higher resolution of the system from 280 ps up to 120 ps. Further, Our setup is being used as one of the experimental tools in the validation task within the Perfect project (Sub-project: Physics Modeling, WP3: long term validation), it is our intention to compare the results obtained from two different setups, in two different labs (Japan/Belgium) but the same operator using the same samples to insure their quality.