主动型氢原子钟原子弛豫时间的测量和分析

氢原子钟的原子弛豫时间是原子系统经过选态去除基态超精细能级（F = 0，m_F = 0）态和（F = 1，m_F = ?1）态原子后，部分氢原子从（F = 1，m_F = 0）态跃迁至（F = 0，m_F = 0）态直至原子系统达到平衡状态所需的时间，该参数反映了原子的寿命，并直接影响氢原子钟的稳定度指标.为了测量主动型氢原子钟的弛豫时间，进而评估其性能，通过Raspberry Pi（RPI）产生时序信号，控制数字衰减器和电离源供电电路的继电器，从而控制微波探测信号的开启和原子束流的通断，并与数据采集等电路组成了氢原子自由感应衰减测试系统.通过对采集的自由感应衰减信号建模拟合，测算了氢原子钟的弛豫时间.该方法对于评估和优化原子线宽，改进主动型氢原子钟稳定度指标具有重要的参考意义.

Measurement and Analysis of Atomic Relaxation Time in Active Hydrogen Atomic Clocks

The atomic relaxation time of a hydrogen atomic clock is the time required for atomic system after the selected state removing the atoms of the ground state hyperfine energy level (F = 0, m_F = 0) and (F = 1, m_F = ?1) state to change from the (F = 1, m_F = 0) state to the (F = 0, m_F = 0) state until the atomic system reaches equilibrium. This parameter reflects the lifetime of atoms and directly affects performance of hydrogen clock. In order to measure the relaxation time of active hydrogen atomic clock and thus evaluate its performance, hydrogen atomic relaxation test system was established, which was composed of a Raspberry Pi (RPI), signal generator, digital attenuation, microwave detection, and data acquisition circuits. RPI generates timing signal to control the relay of digital attenuator and ionization source power supply circuit, so as to control the opening of microwave detection signal and the on-off of atomic beam current. The relaxation time of the hydrogen atomic clock is measured by data fitting of the acquired free induction decay signals. This method is important for optimizing the atomic linewidth and improving the performance of the active hydrogen clock.