The main devices of the PAS laboratory are the lifetime (LT) spectrometers: one of them ensures high time resolution (225 ps), the other one has higher detection efficiency but weaker time resolution (320 ps). To measure the Doppler effect our laboratory is equipped with an HPGe semiconductor detector with large efficiency (25%) and high energy resolution (1.2 keV FWHM). (This setup is actually a normal γ-spectrometer with extended scaling on the registered energy range. The Doppler-coincidence method is also applied occasionally, the direction correlated and goniometer-equipped version has been developed by the PAS group of RMKI.)
The sample-holder cryostate allows to perform LT and Doppler measurements within the temperature range of 90-573K (in vacuum or in gas atmosphere) even simultaneously when applying appropriate geometry. The slow positron generator – which has been developed in the PAS laboratory – is going to perform Doppler measurements in the 0.5 keV – 30 keV energy range using positrons that are focused on samples placed in the rotating sample holder within the target chamber.
The low activity of the ²²Na source and the difficulties of the vacuum bake-out of the positron moderator limit the effective operation presently.
Slow positron generator
(0.5-30 keV, 50-150 positron/s)