The large-acceptance spectrometer TAGX for photoreaction studies at the 1.3-GeV Tokyo electron synchrotron

The study of photoreactions on light nuclei with the TAGX spectrometer started in 1987 using the 20% duty-cycle tagged-photon beam at the 1.3-GeV Tokyo electron synchrotron. TAGX is comprised of a π-sr magnetic spectrometer for detection of charged pions, kaons, and protons and a 0.85-sr time-of-flight spectrometer for neutrons. It has served in the past eight years as a unique medium-energy-resolution multi-particle spectrometer for coincidence experiments to detect such final states as pn, pp, π+ π−, ppn, pp−, and pnπ+ π−: some of which were kinematically-complete measurements of three-particle and four-particle final states. Details of the detector components, their performance, data acquisition, event reconstruction analyses, and detector-acceptance calculations are described together with the results of experience acquired in those experiments. A TAGX improvement in the momentum resolution required for charged particle measurements in the 1-GeV photon energy region is also reported.