HINDA: Development of a Detector Array for Compton Scattering using Polarized Beams and Targets

詹姆斯麦迪逊大学（JMU）的光核物理小组正在杜克大学杜克自由电子激光实验室（DFELL）的高强度伽马源（HI S）设施上进行康普顿散射计划，该实验室由三角大学核实验室（TUNL）运营。 拟议的研究使用光子诱导的反应，调查核子和核子共振的性质。该计划的主要组成部分是使用光束和目标偏振观测的光核反应。康普顿散射计划将由来自14个机构的32名物理学家合作进行。为了进行这一光子散射计划，一个大的接受，高分辨率的射线光谱仪，HINDA，由八个大型碘化钠探测器包围分段碘化钠反符合屏蔽正在建设。沿着在隧道实验室的大型碘化钠探测器，我们正在申请资金购买八个碘化钠屏蔽和电子设备。HIS装置为通过极化和非极化核子及核靶的康普顿散射研究与核子结构有关的基本量打开了一扇新的窗口。这些研究允许提取的电磁极化率的中子前所未有的准确性，并将提供数据，目前未知的数量，如自旋极化率的核子第一次。这些极化率表征了核子对光子的电场和磁场的响应。此外，氦同位素的康普顿散射将允许精确测定3 He和4 He核的极化率。这些研究还将允许有效场论的精确测试，晶格量子色动力学计算和核物理标准模型的预测。碘化钠反符合屏蔽将被运往JMU进行组装，初始测试和校准的JMU本科生。在2006年夏季建造探测器开发实验室和对学生进行培训之后，将在2006-2007学年完成所有八个屏蔽的组装和校准。这完全是一个本科生项目的范围内，不应该强烈受到影响的课程安排在学年期间，因为大部分的时间都花在收集数据。这个时间表补充了预计完成的HI S升级到2006年底和UVa偏振目标在2007年初在TUNL的到来。随着目标在春季安装，HINDA将在2007年夏季安装。HINDA阵列中的探测器将由一个探测器支架支撑，该支架的设计使探测器在目标周围的布置具有很大的灵活性。Tunl最近聘请了一位机械工程师来设计这个支持系统。JMU的学生将在2007年夏天为HI S的系统组装做出贡献。JMU的本科生参与这个项目将对我们的学生有很大的好处。通过配置电子和数据采集系统，然后表征单个探测器的性能，这些本科生将获得宝贵的实验技能。一旦在校园内接受培训，学生将参与HINDA阵列和HI S相关实验硬件的安装。此后，他们将在暑假期间协助收集数据。高级学生还将在该计划的后期阶段协助数据分析。

The photonuclear physics group at James Madison University (JMU) is engaged in a program of Compton scattering at the High Intensity Gamma Source (HI S) facility at the Duke Free Electron Laser Laboratory (DFELL) laboratory at Duke University, operated by the Triangle Universities Nuclear Laboratory (TUNL). The proposed research uses photon-induced reactions to investigate the properties of the nucleon and nucleon resonances. The dominant component of this program is the use of beam and target polarization observables in photonuclear reactions. The program of Compton scattering at HI S will be carried out by a collaboration of 32 physicists from 14 institutions. To carry out this photon scattering program, a large acceptance, highresolution -ray spectrometer, HINDA, consisting of eight large NaI detectors surrounded by segmented NaI anti-coincidence shields is being constructed. Along with the large NaI detectors in-hand at TUNL, we are requesting funding to purchase eight NaI shields and electronics. The HI S facility opens a new window to the study of fundamental quantities related to the structure of the nucleon through Compton scattering from both polarized and unpolarized nucleons and nuclear targets. These studies allow the extraction of electromagnetic polarizabilities of the neutron with unprecedentedaccuracy, and will provide data for the first time on currently unknown quantities such as spin polarizabilities of the nucleon. These polarizabilities characterize the response of the nucleon to the electric and magnetic fields of the photon. Furthermore, Compton scattering from helium isotopes will allow for a precision determination of the polarizabilities of the 3He and 4He nuclei. These studies will also allow for precision tests of effective field theories, lattice quantum chromodynamics calculations and predictions of the standard model of nuclear physics. The NaI anti-coincidence shields will be shipped to JMU for assembly, initial testing and calibration by JMU undergraduates. After construction of the detector development lab and student training during the summer of 2006, the assembly and calibration of all eight shields will be completed during the academic 2006-2007 year. This is well within the scope of a project for undergraduates and should not be stronglyaffected by class schedules during the academic year since most of the time is spent collecting data.This schedule complements the expected completion of the HI S upgrade by the end of 2006 and the arrival of the UVa polarized target at TUNL in early 2007. With the target installed during the spring, HINDA will be installed in the summer of 2007. The detectors in the HINDA array will be supported by a detector stand designed to allow great flexibility in their disposition around the target. TUNL has recently hired a mechanical engineer who will design this support system. JMU students will contribute to the assembly of the system at HI S during the summer of 2007.Undergraduate involvement in this project at JMU will be of enourmous benefit to our students. Byconfiguring the electronics and data acquisition system, and then characterizing individual detector performance, these undergraduate students will gain valuable experimental skills. Once trained on-campus, the students will participate in installation of the HINDA array and associated experimental hardware at HI S. Following this, they will assist in data acquisition during the summer breaks. Advanced students will also assist with data analyzes in the later stages of the program.