Development Of Alkali Metal Potassium Atomic Magnetometer

In recent years, superconducting quantum interference device (SQUID) has the highest sensitivity of the magnetometer (at liquid helium temperature, the sensitivity of1fT/Hz1/2). However, SQUID technology requires expensive cooling equipment and probe, the cost of the instrument is high. In addition, SQUID disturbance is very sensitive to the environment, but also limits its application. With the rapid development of security, mineral exploration, brain magnetic detection of many military and medical areas of the national economy, people began to find the design of lower cost, stronger adaptability to the environment of the new generation. This experiment adopts the minimum collision cross section potassium (K) atoms as the experimental probe, in the absence of spin exchange relaxation (spin-exchange relaxation, free, SERF) mechanism, develops K alkali metal atomic magnetometer, specific work and research results are:The designed magnetic probe is composed of spherical glass cell and room temperature shell. In order to eliminate the cause of collision broadening between the atom and the cell wall, using eighteen of three alkyl chlorosilane (OTS) to coat cell. Constant temperature heat conduction and heat resistance of the shell is made of good boron nitride materials, using S shaped winding heating wires, and thermal grease evenly. Magnetic probe mounted into the vacuum chamber, which makes the light path through the gas chamber, but also to ensure that the mechanical structure of magnetic probe stability and temperature uniformity and stability.Secondly, we developed magnetometer auxiliary circuit, a constant current source circuit to control the current Helmut Hz coil, which has50ppm low temperature drift, the current control precision of10tested A, to achieve the precise control of magnetic field magnetic probe. In order to heat the K atomic vapor cell and keep the temperature constant, we designed the temperature control PID circuit. The use of Huitong, gas chamber temperature acquisition bridge into voltage signal, the amplitude of the PID control circuit and FET circuit of22KHz signal, the amplified input to the amplifier circuit to the heating wire heating. The3minutes of rapid heating from room temperature to200℃. the control precision and has0.1℃.Once more,we used a double photodiode (PD) to receive the probe light out of the Wollaston prism, which is measured by the spin angle probe atomic gas chamber after. The probe which goes through the PD light is very weak, only uA level. So we use OP07chip to build the adjustable signal processing circuit magnification which achieves102-106.Finally, build a pump and probe light path. In order to ensure that the laser output is linearly polarized, and has high enough light intensity, by adjusting light path through a single-mode fiber coupling efficiency to60%, the extinction ratio reached500:1.The experiment obtained the linewidth of93.3nT magnetic field response signal, the actual noise level is3.7pT/Hz1/2.