A Pair Polarimeter for Linearly Polarized High-energy Photons

高能光子偏振态的精确测量是一个重要的课题。杰斐逊国家实验室（JLab）的科学计划包括基础实验，这些实验要求偏振测量至少精确到5%，其中一些实验要求精确到1- 2%。然而，在JLab能量下的所有已知方法都具有低分析能力，并且绝对精度低于批准和预期的物理程序所需的精度。所提出的旋光仪是目前唯一的解决办法。偏振计将有一个实验的不对称性约为1.7的能量范围从几十兆电子伏到几个GeV。该旋光仪结构简单、紧凑，并且其成本将低于根据任何其他可用方法制造的旋光仪。我们已经制造并测试了两个原型。检测器和电子器件的性能符合预期，测量的分析能力与预测的一样大。然而，还需要更多的改进;我们需要在对产生理论和计算、数据采集和分析软件以及探测器硬件方面做更多的工作。拟议的研究和教育计划将提高北卡罗来纳州中央大学物理和科学课程的竞争力，并改善教师和学生招聘的条件。设备齐全的学习环境和在核和计算物理领域的原始研究，以及计算机建模，将增加更具竞争力的学生的产量。新兴的科学进步和机会也将为我们的毕业生提供职业选择的灵活性，并为我们的学生进一步的研究生学习做好充分的准备。此外，我们预计，该计划将刺激在其他方向的研究，从而支持非洲裔美国研究生和本科生的培训继续扩大。

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.