DescriptionA series of near-threshold pion photoproduction measurements are currently underway at the Tagged-Photon Facility at MAX-lab, the Swedish National Electron Accelerator Facility located at Lund University in Lund, Sweden. The photon beam used in the experiment is produced via bremsstrahlung radiation when a 200 MeV pulse-stretched electron beam strikes a 300 mm aluminum foil. To determine the absolute probability for producing pions, the exact number of photons striking the target must be known. This information is determined using the photon-tagging technique, where the momenta of the
post-bremsstrahlung electrons are determined together with the number of radiated photons, their energies and their relative timings. An important quantity in the photon-tagging process is the tagging efficiency. The tagging efficiency is the ratio of the number of photons striking the target to the total
number of photons produced at the radiator. The photon-tagger is divided into multiple channels, each corresponding to diffierent photon energies, and each of these channels has a tagging efficiency associated with it. For the May 2009 experiment, the tagging efficiency was measured daily. At the conclusion of the experiment, the collected tagging efficiency data were analyzed on a channel-by-channel basis, and the results are presented in this paper.
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