An investigation of positrons interacting with solid argon, krypton and xenon

With this article we intend to shed some light on all the important characteristics of the up-to-date most efficient positron moderators, the rare gas solids. We stress on the importance of the impurities in the performance of the solid rare gas moderators. The impurity factor is linked with the crystalline changes to explain the effect of annealing, and we demonstrate the role of impurities in the endurance. Significant increase in the low energy positron yield is observed after repeated anneals. The positron energy distributions from Ar, Kr, and Xe moderators are measured to be about 2 eV (FWHM).