Positron annihilation 2D ACAR device using position-sensitive photoelectron multiplier tube

For a positron annihilation 2D ACAR device, the γ ray detector with good position resolution and detection efficiency is indispensable. The authors have examined the performance of the new type γ ray detector, in which the scintillator with high detection efficiency and high luminance is attached to a position-sensitive photoelectron multiplier tube (PS-PMT). As the result, it was found that the detector of attaching many fine columnar BGO scintillators being bundled to a PS-PMT is suitable to the detector for the 2D ACAR device. The 2D ACAR device using this detector was made in the Radioisotope Center, University of Tokyo. The position-sensitive γ ray detector and the method of detecting position are explained. The arrangement of the 2D ACAR device including two detectors and the circuit are shown. The two-dimensional angular correlation of KI at 14K measured with this device is shown. The momentum resolution was estimated to be about 1.2 x 10-3 mc from the width of a positronium peak. 70 counts/s on average was obtained under the conditions of 30 mCi Na-22 source and 7.5 k gauss magnetic field. The detector is compact, its efficiency is high, and price is low. (K.I.)