High precision photon flux determination for photon tagging experiments

The Jefferson Laboratory PrimEx Collaboration has developed and implemented a method to control the tagged photon flux in photoprocluction experiments at the 1% level over the photon energy range from 4.9 to 5.5 GeV. This method has been successfully implemented in a high precision measurement of the neutral pion lifetime. Here, we outline the experimental equipment and the analysis techniques used to accomplish this. These include the use of a total absorption counter for absolute flux calibration, a pair spectrometer for online relative flux monitoring, and a new method for post-bremsstrahlung electron counting. (C) 2014 Elsevier B.V. All rights reserved.