高准确度铯-氦光泵磁强计的粒子数密度配比研究

Research on the number density ratio of Cs/~4He in the Cs-He optical magnetometer

为研发高准确度铯-氦光泵磁强计探头的制备工艺,该文通过分析铯、氦两种混合物质的气室内各组分间的潘宁电离和自旋交换碰撞过程,从理论上给出铯-氦磁强计的最佳粒子数配比关系N_(Cs)∶N_(He)≈1.9∶1。为验证该理论,搭建一套铯-氦磁强计系统,分别通过调节温度和激励微波来控制铯原子和氦原子的数密度,当磁共振信号达到最优化状态时,测量铯氦粒子数比值为N_(Cs)∶N_(He)≈1.6∶1。考虑到理论计算时对亚稳态氦原子退极化率的保守估算和实验过程中对气室内部温度的测量误差,该理论值和实验结果吻合度较为一致。研究结果表明:在制作铯-氦光泵磁强计探头气室时,铯原子与亚稳态氦原子的原子数密度比值应该介于1.6~1.9之间。

In order to develop the technique of making sensors for the Cs-He optical magnetometer, the Penning ionization and spin -exchange collision process happening in the cesium -helium mixture vapor chamber are analyzed, and the optimal number density ratio of the mixture is calculated, which gives NCs： NHc≈ 1.9：1. To check this theoretical result, a Cs-He magnetometer system is built, where the number density of Cs and He can be controlled by adjusting the temperature and microwave discharge respectively, when the magnetic resonance signal reaches the best performance, the number density ratio of the mixture is measured, which is NCs： NHe≈1. 6： 1. Considering the upper limit estimate of the depolarization of metastable helium in the theory and the temperature error of the chamber center in the experiment, the theoretical number fits well with the experimental results. The results show that the optimal ratio of Cs/^4He number density of a Cs-He magnetometer should be between 1.6 and 1.9.