Farhad Zolfagharpour - Department of physics, University of Mohaghegh Ardabili, Ardabil, Iran
Roghaye Sohrabi - Department of physics, University of Mohaghegh Ardabili, Ardabil, Iran
Meysam Ghaebi - Department of physics, Univer sity of Damghan, Damghan, Iran
Maryam Noorani - Department of physics, University of Mohaghegh Ardabili, Ardabil, Iran

In this paper, coincidence intensities of 511 keV gamma rays yieldedfrom electron and positron decays emitted from 22Na source, aremeasured using two NaI detectors with timing response of 4 microseconds. The experiment is done under angles of 90º, 180º and 270ºwith respect to detectors in two situations: First they are shielded usinga lead shield and a lead window and then they are unshielded. Theresultant gamma ray spectra in detectors are recorded in coincidenceand normal modes. Due to Campton scattering, the gamma rays can bescattered in angles other than 180º and with increasing or decreasing thescattering angle, the recorded gamma ray intensities decrease. Ourresults show that in the case in which the lead window is consideredand the gamma rays are coincident, with changing the scattering angle,the peak area in gamma spectrum in 511 keV energy reduces to zerofaster than the case in which the lead window is not considered. Thisshows that using the lead window, the Campton scattering reduces.Also, without the lead window, the recorded gamma ray intensity interms of the scattering angle, is compatible with Klein-Nishinaequation.

Coincidence, NaI detector, Positron, 22Na source