Suppression of Nonuniform Magnetic Fields in Magnetic Shielding System for SERF Co-Magnetometer
Yang Fu, Zhuo Wang, Xing Li, Wenfeng Fan, Jiasen Ruan, Haoying Pang
Abstract
Spin-exchange relaxation-free (SERF) co-magnetometer typically use a low-noise magnetic shield system, which is composed of outer μ-metal shields and inner low-noise magnetic shield, to provide the required magnetic environment. Proper degaussing is essential for the co-magnetometer to obtain low remanence and field gradient. In this paper, an improved design method of degaussing device suitable for the SERF co-magnetometer is proposed, which considers the degaussing performance demand of multi-material magnetic shields and the introduction of magnetic noise by metal materials. Based on this, a coil-shaped degaussing device in separate type is designed and compared with the existing detachable pole-shaped degaussing device. The experimental results show that this degaussing device can reduce the residual magnetic field in the three axis directions by more than 65%, and reduce the magnetic gradient within ±10mm of the shields center by more than 80%. As a result, the non-uniform magnetic fields can be effectively reduced, which greatly suppress the electron relaxation so that the signal-to-noise ratio is improved. Furthermore, the signal noise of the SERF co-magnetometer is reduced by about 25%.