Automated spectrometer for measuring annihilation photon angular distribution

Spectrometer for measuring annihilation photon angular distribution (APAD) is described. The spectrometer is intended for investigations into hydrogen and inert gas interaction with materials in particular, for determining helium solubility in metals at the level of several deca-thousandths of atomic per cent. The unit is long-gap with vertical gap position. The distance from sample to scintillator is 2 m with the gap width being 1-2 mm. APAD spectrometer time resolution is 50 ns. The photomultiplier is optically connected with NaJ(Tl) 63x250 mm scintillator. 460 MBq activity 22Na isotope is used as positron source