Figure 1
Schematic of the experimental setup.
The setup is similar to the one developed by Brown, Smullin, Kornack, and Romalis16. The vapour cell is at the centre of the co-magnetometer. A vertical pump beam and a horizontal probe beam are used to polarize atoms and probe atom spins. The vapour cell is heated, and magnetic field shields are used to shield atom spins from magnetic fields. The core of the co-magnetometer is configured on a vibration isolation platform. A bell jar, where air fluctuation is reduced, is used to enclose the laser beam in vacuum. The apparatus is constructed on a rotary platform, which is utilized to rotate the sensitive axis of the co-magnetometer around the z-axis. To improve the sensitivity, the sensitive axis is fixed to the east direction to reduce the input rotation of the earth to approximately 0 as the co-magnetometer is constructed in our laboratory at a certain latitude and longitude in Beijing. Moreover, the co-magnetometer can be calibrated by the rotation of the earth. BE: beam expander, PBS: polarization beam splitter, GT: Glan-Thompson polarizer, PD: photo detector, PEM: photo elastic modulator, TA: tapered amplifier, DAVLL: dichroic atomic vapour laser lock, DBR: distributed Bragg reflector, and DFB: distributed feedback.
