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

詹姆斯·麦迪逊大学的光核物理小组在杜克大学杜克自由电子激光实验室的高强度伽马源(HI S)设施中从事康普顿散射计划，该实验室由三角大学核实验室(TUNL)运营。这项拟议的研究使用光子诱导反应来研究核子和核子共振的性质。该程序的主要组成部分是在光核反应中使用光束和目标的偏振观测数据。在HI S，康普顿散射计划将由来自14个机构的32名物理学家合作执行。为了执行这一光子散射计划，正在建造一台可接受的大型高分辨率射线光谱仪HINDA，它由八个大的NaI探测器组成，周围环绕着分段的NaI反符合屏蔽。连同手中的大型NaI探测器在Tunl，我们正在申请资金购买八个NaI屏蔽体和电子设备。HI S装置打开了一扇新的窗口，通过极化和未极化的核子和核靶的康普顿散射来研究与核子结构有关的基本量。这些研究使得能够以前所未有的精度提取中子的电磁极化率，并将首次提供关于目前未知的量的数据，如核子的自旋极化率。这些极化率表征了核子对光子电场和磁场的响应。此外，氦同位素的康普顿散射将允许精确地确定3He和4He原子核的极化率。这些研究还将允许对有效场论、晶格量子色动力学计算和核物理标准模型的预测进行精确测试。NaI反符合屏蔽将被运往JMU，由JMU的本科生进行组装、初步测试和校准。在2006年夏季建造探测器开发实验室和学生培训之后，所有8个屏蔽罩的组装和校准工作将在2006-2007学年完成。这完全在本科生项目的范围内，不应受到学年课程表的强烈影响，因为大部分时间都花在收集数据上。这一时间表是对预期于2006年底完成的HI S升级工程和2007年年初在TUNL实现的UVA极化目标的补充。随着目标在春季安装，欣达将于2007年夏天安装。欣达阵列中的探测器将由探测器支架支撑，其设计允许在目标周围部署探测器时具有极大的灵活性。TUNL最近聘请了一名机械工程师来设计这个支撑系统。JMU的学生将在2007年夏天为HI S的系统组装做出贡献。本科生参与JMU的这个项目将使我们的学生受益匪浅。通过配置电子学和数据采集系统，然后对各个探测器的性能进行表征，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阵列和相关实验硬件在HI S的安装。随后，他们将在暑假期间协助数据采集。高级学生还将在课程的后期阶段协助进行数据分析。

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.