On-line Measurement of Beam Intensity in Experiment of Ionization Cross Section Induced by Positron

In this paper, the HPGe detector was used to collect the annihilation photon generated during positron collision with a thick Ti target. In combination with the detection efficiency of HPGe detector for the 511 keV photon annihilated by the positron emitted from the ²²Na standard source placed at the collision point, the on-line results of positron beam intensity in the measurement of Ti inner-shell ionization cross section impacted by 8-9.5 keV positrons were obtained. The results show that the positron beam intensity generated by the slow positron beam device based on the ²²Na standard source is unstable. The positron beam intensity decreases with measurement time. Besides, the slight fluctuation exists during the experiment. Therefore, it is necessary to apply the on-line monitoring technique in measuring positron beam intensity for obtaining accurate atomic inner-shell ionization cross section induced by low energy positron.