Internal-source method of measuring absolute pair-production cross sections

摘要

The history,detailed description and results obtained using a unique but simple method of measuring absolute pair-production cross sections is reviewed.These activities which occurred between 1973 and 1985 yielded results for photons on targets of Z = 26,29,50,82,and 92 for photons with energies of 1.1205,1.3325,1.8362,and 2.6145 MeV.They were measured for these energies and for 1.077 MeV for targets up to Z = 82.The cross sections deviated significantly from theoretical calculations for energies near threshold.The discrepancy was later confirmed and an explanation suggested.