A Pair Polarimeter for Linearly Polarized High-energy Photons

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The precise measurement of the polarization of high energy photons is an important topic. The scientific program at the Jefferson National Laboratory (JLab) includes fundamental experiments that require polarization measurements to be accurate to at least 5%, and some of them require an accuracy of 1-2%. However, all known methods at JLab energies have low analyzing power, and the absolute accuracy is below that required for the approved and anticipated physics programs. The proposed polarimeter is at the present the only solution. The polarimeter will have an experimental asymmetry of approximately 1.7 for an energy range from a few tens of MeV up to several GeV. The polarimeter is simple in construction, compact, and its costs will be lower than for polarimeters built according to any other available method. We have already built and tested two prototypes. The performance of the detectors and the electronics met expectations and the measured analyzing power is as large as predicted. However, more improvements are needed; we need to do additional work on pair production theory and calculations, data acquisition and analyzing software, and the detector hardware. The proposed research and education program will increase competitiveness of the North Carolina Central University physics and science programs, and improve conditions for the faculty and student recruitment. Well-equipped learning environment and the original research in the fields of nuclear and computational physics, and computer modeling, will increase production of more competitive students. Emerging scientific advances and opportunities will also provide flexibility in career choices of our graduates and adequately prepare our students for further graduate studies. Furthermore, we expect that this program will stimulate research in additional directions, and thereby support the continuing expansion of training for African American graduate and undergraduate students.