Development of a miniaturized SQUID measuring systems for an experiment to measure the electric dipole moment of the neutron

在下一代中子电偶极矩测量实验中，磁场的精确控制至关重要。特别是，通过中子存储室的垂直梯度需要精确地确定，以避免所谓的几何相位，它与存储在腔室内的超冷中子（UCN）的系统轨迹相结合。这些被解释为假的电火花加工信号，并且在上一代的实验中已经在10-26 ecm水平上观察到。基于最近研制的大体积3He旋进腔，可以很精确地确定这一梯度。然而，这些3He室也必须用磁力计读出。PTB Berlin的研究已经表明SQUID磁场传感器最适合这一目的，因为它们在典型进动频率（10-50 Hz）下的噪声特性< 2 fT/。在这个建议的框架内，应该开发一个小型化的SQUID系统来读取3He岁差信号。此外，它应该能够提供UCN进动室附近磁场的方向信息，并应作为129Xe磁力计的中心部件。除了在nEDM实验中的应用之外，新的SQUID低温恒温器可能在各个研究领域有各种应用，例如生物磁学。

In a next generation experiment to measure the electric dipole moment of the neutron (nEDM) accurate control of magnetic fields is crucial. In particular, the vertical gradient through the neutron storage chamber needs to be determined precisely to avoid so-called geometric phases, which appear in combination with systematic trajectories of stored ultra-cold neutrons (UCN) in the chamber. Those are interpreted as false EDM Signals and have been observed on the level of 10-26 ecm in the previous generation of experiments. Based on recently developed large volume 3He spin precession chambers, such a gradient can be determined with great accuracy. However, also these 3He chambers must be read out with means of magnetometers. Investigations at PTB Berlin already showed that SQUID magnetic field sensors are best suitable for this purpose, as their noise characteristics at typical precession frequencies (10-50 Hz) are < 2 fT/ . Within the framework of this proposal a miniaturized SQUID System should be developed to read out 3He precession Signals. In addition it should be capable of delivering directional information of magnetic fields in vicinity of the UCN precession chambers and should act as the central component of a 129Xe magnetometer. Next to the use in the nEDM experiment, the new SQUID cryostat potentially has a variety of applications in various fields of research, e.g. biomagnetism.