Omnidirectional magnetometer in Brazil for dark matter search within GNOME

用于奇异物理搜索的光学磁力计全球网络（GNOME）是一个寻找暗物质签名的国际合作（例如，由轴子或类轴子粒子形成的宏观结构）。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建立在从分布在地球仪周围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个活跃的“站”组成，即，先进的、磁屏蔽良好的OPM设置，持续将数据流传输到协作服务器。从第一个多站长期运行的分析，在目前的状态网络的局限性变得明显：所有的站都位于北方。此外，所有有源磁力计都表现出所谓的“死区”，即空间中的角度范围，其中传感器对于外来（和磁）耦合是盲目的。这导致地球坐标系中的全局灵敏度降低且各向同性灵敏度显著降低。在该项目中，我们建议开发一个新的GNOME台站，以弥补这两个局限性：首先，该台站将安装在巴西国家天文台的瓦苏拉斯地磁观测台，使其成为世界上第一个南半球台站。因此，它将在重建奇异耦合的时空过程中获得很大的权重。它将利用现场现有的补充传感器系统（例如，瓦苏拉斯是观测地球磁场的国际网络INTERMAGNET的一部分），通过先进的否决方法（有待开发和测试）进一步提高网络的数据质量。其次，我们想开发和研究一种新的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（全向）同时敏感，即没有死区。我们希望使用基于Leibniz IPHT制造的几个小型化碱蒸汽电池的布置来实现这一点，该布置凭借一种新方法可以在共同的磁屏蔽内无干扰串扰地操作。在项目的第一阶段，将在瓦苏拉斯安装一个经过试验和测试的OPM装置，以确保GNOME网络能够及时获得来自南半球的数据。全方位传感器在实验室成功演示后，巴西站将在项目结束时升级到这一方案。 所有这些将使GNOME能够以前所未有的灵敏度对暗物质模型进行实验测试。

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.