Precision field characterization for the next generation measurement of the neutron EDM

在这项计划中，我们计划实现一个磁场测量系统，用于下一代测量中子电偶极矩(EDM)，灵敏度为10-28ecm。该系统将用于两个目的：(I)在磁稳定环境内的磁场线圈和组件的各种场的表征，在安装期间和之后，每个组件在其最终位置离线。这对于真空室内的电火花加工腔部件、UCN光学元件和硬件尤其重要。对于内部部件，污染物大小的优值系数在3厘米处最大为1pT，从而产生几何相位效应。目标(二)是在线测量电火花加工过程中的磁场。在这里，每个传感器在100FT级别上的长期性能和在10-4rad倾斜级别上的场方向分辨率是必要的。这有助于在实验运行时使用矢量信息跟踪来自大小局部源的渐变形状的变化。由于所有其他现场(共)磁力仪只提供平均信息，这对于了解系统效应至关重要。为此，我们使用全光学Cs磁强计系统进行了测试，该系统非常适合在线和离线现场测量，而不会因感应射频或磁化硬件组件而产生噪音。在这个项目中，我们希望在随后的3个阶段为这两个目标开发一套这样的探测器。第一阶段是传感器及其运行模式的进一步优化，第二阶段是现场安装更多的传感器，用于离线和在线现场测绘和调试，第三阶段是对其他系统的操作、表征和测试。

In this proposal we plan to realize a magnetic field measurement system for a next generation measurement of the neutron's electric dipole moment (EDM) with a sensitivity of 10-28 ecm. The system will be deployed for two purposes: (i) characterization of all kinds of fields from field coils and components inside the magnetically stabilized environment offline during installation and after of each component at their final location. This is in particular important for the EDM chamber parts, UCN optics and hardware inside the vacuum chamber. The figure of merit for the magnitude of contaminations is maximum 1 pT at 3 cm distance for inner components, giving rise to geometric phase effects. Goal (ii) is the measurement of magnetic fields during the EDM measurement online. Here, the long-term performance on a 100 fT level per sensor and the resolution of field direction on the 10-4 rad tilt-level is necessary. This helps to track changes of the shape of gradients from large and small localized sources using vector information while the experiment is operating. As all other in-situ (co-)magnetometers only provide averaged information, this is critical for the understanding of systematic effects. For this purpose we made tests with a fully optical Cs magnetometer system that is perfectly suitable for in-situ measurements online and offline without producing noise due to induced RF or magnetized hardware components. Within this project we would like to develop a set of such probes for both goals in 3 subsequent stages. Stage 1 is further optimization of sensors and their operation modes, stage 2 is the installation of a larger set of sensors on site for offline and online field mapping with commissioning and stage 3 is the operation, characterization and test against other systems.