星载氢原子钟用多段线圈式C场的仿真及应用

Simulation and Application of Multi-section Coil for C Field Used in Space Passive Hydrogen Maser

星载氢原子钟具有频率稳定度高、频率漂移率低的优点,在卫星导航定位和频率计量中得到了广泛应用。星载氢原子钟的腔泡系统用于实现氢原子的量子跃迁及其信号采集,原子跃迁信号幅度直接决定了系统的信噪比,进而影响整机性能指标,所以腔泡系统是星载氢原子钟的核心组件。目前,星载氢原子钟腔泡系统主要采用直螺线管来产生原子跃迁所需的C场。由于星载氢原子钟物理部分的结构限制,直螺线管的磁场均匀度有进一步提高的空间。探讨使用多段线圈代替直螺线管用于产生C场的可行性。首先对多段线圈产生的磁场进行理论分析计算,同时使用ANSYS电磁场仿真软件对多段线圈的各项参数进行仿真和优化,包括各段长度、段数、间距以及匝数、内径和总长度等。然后优选磁场均匀度较好的线圈配置参数,可将C场的非均匀度由直螺线管约10%降低到多段线圈约1%。根据仿真优化结果建立了试验九段线圈,对比测试了原子跃迁信号增益,同时结合电路部分进行闭环测试,对频率稳定度指标进行了对比。实验结果表明,原子跃迁信号可有效提升,阿伦方差在中短稳(1~1000 s)表现更好。此项工作为星载氢原子钟整机性能指标的进一步提升打下了基础。

Space passive hydrogen maser(SPHM)has the advantages of high frequency stability and low frequency drift.It has been widely used in the navigation systems and frequency calibration.The quantum transition of hydrogen atoms and its signal detection are realized in the cavity-blub assemble of the spaceborne hydrogen atomic clock.Atomic transition signal amplitude of SPHM directly determines the system signal to noise ratio,and thus affects system performance,which makes cavity-bulb assemble one of the most important parts of SPHM.Straight solenoid is widely used in cavity-bulb assemble of SPHM to generate the constant magnetic field(C field)for atomic transition.Due to structural restriction of physical package,there is improvement potential for homogeneity of C field.This paper discusses the feasibility of using multi-section coil for generating the C field in SPHM.Firstly,the magnetic field generated by multi-section coils is theoretically analyzed and calculated.Then simulation and optimization of the parameters of the multi-section coil is carried out by ANSYS electromagnetic simulation software,the length of each section,their quantity,spacing,turns,diameter and total length.Design of multi-section coil with better homogeneity for the C field can be given by the simulation software.Inhomogeneity of about 1%of the C field is realized comparing to about 10%of the straight solenoid.According to the optimization results,the experimental nine-section coil was manufactured.The testing and comparison of atomic transition signal gain with diffident C field were carried out.Meanwhile,the closed-loop test was done in combination with the electronic package,and frequency stability of SPHM was measured and compared.Experimental results show that atomic transition signal gain can be effectively increased with the use of multi-section coil,and frequency stability is better in the middle and short-term stability(1-1000 s),which is beneficial to further performance improvement of SPHM.