Omnidirectional magnetometer in Brazil for dark matter search within GNOME

用于奇异物理搜索的全球光学磁强计网络(GNOME)是一个通过寻找光泵磁强计(OPM)中的自旋耦合来寻找暗物质特征(例如，由轴子或类似轴子的粒子形成的宏观结构)的国际合作组织。由于在单个磁力计中不可能区分外来相互作用和局部磁场波动的影响，GNOME建立在从分布在全球各地的传感器阵列检测时空相关性的基础上。在其当前状态下，该网络由12个活动的“站”组成，即复杂的、磁屏蔽良好的OPM设置，不断地向协作服务器传输数据。从对第一个多站长期运行的分析中，可以明显看出当前状态网络的局限性：所有站都位于北半球。此外，所有的有源磁力计都会出现所谓的“死区”，即空间中的角度范围，即传感器对外来(和磁性)耦合是盲目的。这导致全球范围内的敏感度降低，地球坐标系中的各向同性敏感度显著降低。在这个项目中，我们建议开发一个新的GNOME站来弥补这两个限制：首先，该站将安装在巴西国家天文台的Vassouras地磁观测站，使其成为世界上第一个南半球站。因此，它将在重建奇异耦合的时空过程中获得强大的权重。它将通过使用现场提供的补充传感器系统(例如，Vassouras是国际地球磁场观测网络的一部分)的高级否决方法(有待开发和测试)，进一步提高网络的数据质量。其次，我们想要开发和研究一种新颖的OPM工作方案，它不仅在单一方向上敏感，而且在所有三个方向(全方位)上都同时敏感，即没有死区。我们希望使用基于莱布尼茨IPHT制造的几个小型化碱性蒸汽室的布置来实现这一点，通过一种新的方法，可以在公共磁屏蔽内操作而不受干扰串扰。在该项目的第一阶段，将在瓦苏拉斯安装久经考验的OPM系统，以确保来自南半球的数据将及时提供给GNOME网络。在实验室成功演示全向传感器后，巴西站将在项目结束时升级为该方案。所有这些都将使GNOME能够以前所未有的灵敏度试验性地测试各类暗物质模型。

The Global Network of Optical Magnetometers for Exotic physics searches (GNOME) is an international collaboration hunting for signatures of dark matter (e.g., macroscopic structures formed by axions or axion-like particles) by looking for spin couplings in optically pumped magnetometers (OPM). Since in a single magnetometer it is not possible to discriminate an exotic interaction from the effect of a local magnetic field fluctuation, GNOME builds on detecting spatio-temporal correlations from an array of sensors, distributed around the globe. In its current state, the network consists of 12 active “stations”, i.e., sophisticated, magnetically well-shielded OPM setups, continuously streaming data to the collaboration server. From the analysis of first multi-station long-term runs limitations in the current-state network became apparent: All stations are located on the northern hemisphere. Moreover, all active magnetometers exhibit so-called “dead zones”, angular ranges in space, in which the sensors are blind for exotic (and magnetic) couplings. This leads to a reduced global and significantly less isotropic sensitivity in the Earth's coordinate system. Within this project, we propose to develop a new GNOME station to remedy these two limitations: Firstly, the station will be installed at the Vassouras geomagnetic observatory of the Observatorio Nacional, Brazil, making it the world's first station in the southern hemisphere. It will thus gain a strong weight in the reconstruction of the spatio-temporal course of exotic couplings. It will further improve the data quality of the network through advanced vetoing methods (to be developed and tested) using complementary sensor systems available on site (e.g. Vassouras is part of INTERMAGNET, the international network for observing the Earth's magnetic field). Secondly, we want to develop and investigate a novel OPM working scheme which is not only sensitive in a single direction, but in all three directions (omnidirectional) simultaneously, i.e. has no dead zones. We want to achieve this using an arrangement based on several miniaturized alkali vapor cells manufactured at Leibniz IPHT, which, by virtue of a new method, can be operated free of interfering crosstalk within a common magnetic shielding. Within the first phase of the project, a tried and tested OPM setup will be installed in Vassouras to ensure that data from the southern hemisphere will be available to the GNOME network in a timely manner. After the successful demonstration of the omnidirectional sensor in the laboratory, the Brazilian station will be upgraded to this scheme at the end of the project. All this together will allow GNOME to experimentally test classes of dark matter models with hitherto unprecedented sensitivity.