Miniature quad-channel spin-exchange relaxation-free magnetometer for magnetoencephalography

Li Jian-Jun^{1, 2}, Du Peng-Cheng^{1, 2}, Fu Ji-Qing³, Wang Xu-Tong^{1, 4}, Zhou Qing⁴, Wang Ru-Quan^{1, 2, ‡}

Schematic diagram of magnetic sensitivity measurements. The sensor is placed in the center and parallel to the field of the Helmholtz coil that is wrapped around a slotted cylinder made of teflon.