Research And Development Of An Ultra-High Sensitivity Potassium Magnetometer In Spin-Exchange Relaxation-Free Regime

The detection of magnetic field has a long history,of which the weak magnetic field detec-tion is an important branch that can be well applied in medicine,military,industry and basic re-search in phy sics.In recent years,the superconducting quantum interference device (SQUID) has become the most sensitive detector with a sensitive limit to 1 fT/Hz-1/2.However,SQUID has not been widely adopted due to the requirement of expensive refrigeration equipment to keep the superconducting state.A new spin-exchange relaxation-free (SERF) atomic magnetometer,with no requirement of expensive refrigeration equipment,and theoretical magnetic field sensitivity of 0.01 fT/Hz-1/2,comes up.To the best of our knowledge,the best sensitivity of 1 fT/Hz-1/2 is realized by Romalis’group at Princeton University,while the sensitivity of our instrument is 8 fT/Hz-1/2.Up to now,this sensitivity is best at home.The main results of this study are as follows:1.The signal intensity and reliability are directly affected by frequency stability of the probe laser in a highly detuned system.The laser lock-in accuracy of 100 MHz is achieved(limited by wavemeter) by lock-in of virtual PID based on Lab VIEW.2.It is difficult to fix the cell under the non-magnetic and high temperature environment.The stabilized temperature and optical path were achieved by making the cell holder of boronnitride and the tetrafluoroethylene(TFE).3.It is necessary in a non-magnetic environment for the atomic magnetometer.Residual field is less than 1 nT in the magnetic shield cylinder,whose magnetic shielding effectiveness is 105.4.The accuracy of 0.01℃(limited by Thermoscope) is controlled by the PID feedback.And temperature is visualized by the Lab VIEW platform.5.The previous manual system was improved.Automatic measurement and data acquisition are achieved on the Lab VIEW platform.6.The larmor precession frequency in the SERF and the non-SERF regime are demon-strated. And the sensitivity of the atomic magnetometer is showed in the SERF regime.