Entwicklung eines Mehrkammer-(Ko)Magnetometers mit 199Hg für eine neue Messung des Neutron EDM

精密磁强计是下一代中子电火花加工测量的关键部分，其灵敏度目标为10-28 ecm。在这个提议中，我们描述了一种独特的多室（共）磁强计装置，它可以光学地读出极化199Hg在磁场中的自旋进动频率。它的主要特点是四个大容量磁力计单元的垂直堆叠和基于激光的读出和泵浦方案。该项目的主要目标是提供(i)在nEDM测量运行期间的现场在线磁场测量，要求灵敏度< 10 fT，每个磁力计单元积分时间为250 s； （ii）关于主磁场垂直梯度的信息。在以前的实验中已经证明，使用汞放电灯可以实现一个磁强计电池40 fT的灵敏度。使用激光作为光源将提供更高的泵浦功率和稳定性，这两者都将大大提高信噪比，并使我们能够以更高的精度提取Hg的进动频率。由于我们完全控制了激光的所有特性，我们也有独特的可能性来研究与读出光相关的系统效应。从所有四个单元获得的数据的组合使我们不仅可以获得平均磁场，还可以获得主磁场可能的垂直梯度和畸变。在这个项目中，我们希望在三个阶段开发一个满足这两个目标的系统。第一阶段是利用现有的单电池测试装置对激光性能和汞电池性能进行优化。第二阶段包括在磁屏蔽环境中安装磁力计并扩展到多个单元，以及与其他磁力计系统进行测试，第三阶段是实施中子EDM实验和操作的最终实验设置。

Precision magnetometry is a crucial part for a next-generation measurement of the neutron EDM with a sensitivity goal of 10-28 ecm. In this proposal, we describe a unique multi-chamber (co-)magnetometer setup which reads out the spin precession frequency of polarized 199Hg in a magnetic field optically. Its main features are a vertical stack of four large-volume magnetometer cells and a laser-based read-out and pumping scheme. The main goals of the project are to provide (i) online magnetic field measurements in-situ during nEDM measurement runs with the required sensitivity of < 10 fT for 250 s integration time per magnetometer cell and (ii) information about vertical gradients of the main magnetic field. It has been demonstrated in previous experiments that a sensitivity of 40 fT for one magnetometer cell is achievable using Hg discharge lamps. Using a laser as lightsource instead will provide significantly higher pumping power and stability, both of which will greatly increase the signal-to-noise ratio and allow us to extract the precession frequency of the Hg with higher precision. Since we have full control over all of the laser's properties, we also have unique possibilities to study systematic effects connected to the read-out light. The combination of data obtained from all four cells gives us access to not only the mean magnetic field but also to possible vertical gradients and distortions of the main magnetic field. Within this project we want to develop a system that meets both goals in three stages. Stage 1 is the optimization of laser performance and Hg cell properties using an existing test setup with one cell. Stage 2 consists of the installation of the magnetometer in a magnetically shielded environment and the expansion to multiple cells, as well as testing against other magnetometry systems and stage 3 is the implementation into the final experimental setup of the neutron EDM experiment and operation.