空间冷原子钟相关物理与技术研究
文献类型：学位论文
| 作者 | 项静峰 |
| 文献子类 | 博士 |
| 导师 | 刘亮 |
| 关键词 | 冷原子钟 Cold Atom Clock 光学系统 Optical System 激光稳频 Frequency Stabilization of Laser 磁光阱 Magneto-optical Trap 弹性碰撞 Elastic Collision |
| 其他题名 | The Physics and Technologies Related to Space Cold Atom Clock |
| 英文摘要 | 本文的主要内容是作者在攻读博士学位期间完成的主要工作，包括对空间冷原子钟地面样机的改造并开展相关物理实验，研制应用于冷原子钟的激光稳频系统并改进稳频系统的性能，开展空间冷原子钟的地面测试实验及相关的物理研究。 原理样机改造工作包括对87Rb空间冷原子钟地面样机的光学平台、时序控制和激光稳频等部分进行改进；重新设计了光学平台上的光学机械件，重新布局了光学平台上的光学器件，获得了稳定的激光输出；重新构建了时序控制系统，新的时序控制系统更易扩展和更新，满足实验室环境下不同实验的需求。在改进后的空间冷原子钟地面样机上，对光抽运选态方案进行了实验验证，最终使用光抽运选态方案获得了Ramsey条纹。 针对地面样机的光学平台上所采用的商用外腔半导体激光器，构建了基于DSP技术的自动稳频系统，实现了外腔半导体激光器自动稳频，可以实时评估激光器的锁定情况，提高了激光器的长期运行能力，并且在激光器失锁后可以及时重新锁定，满足空间冷原子钟地面样机实验的需求。为进一步提高稳频激光的性能，对激光稳频系统中限制环路带宽的主要因素进行分析，利用外腔半导体激光器的高速电流调制端口，使用射频信号（20 MHz）直接调制激光器的频率，实现了对激光稳频系统环路带宽的拓展，提高了稳频系统对激光较高频率噪声的抑制能力。使用20 MHz调制频率的稳频系统对傅里叶频率为5 kHz处的频率噪声的抑制度达到了20 dB以上，对激光频率稳定度的测量结果也表明对较高频率处的激光频率噪声抑制可以提高稳频激光的短期稳定度。 空间冷原子钟的地面测试实验包含三个方面工作：（1）、考虑到空间不同于地面的磁场环境，在地面模拟空间周期性变化磁场，验证了空间冷原子钟磁屏蔽及磁场自动补偿系统，确定了相应的反馈系数；（2）、在地面进行不同速度的冷原子抛射实验，测试了不同的抛射参数；（3）、从理论和实验分析了造成慢速抛射时冷原子数衰减的可能原因：冷原子与真空中残余气体的碰撞损失。使用质谱仪对背景真空中的残余气体进行了分析。从理论和实验两方面对背景真空中残余气体与冷原子数损失率之间的关系进行分析和研究，主要分为两种情况：处于磁光阱中的冷原子以及自由飞行过程中的冷原子。实验结果与理论计算符合得很好，验证了理论模型，这有助于进一步分析导致空间冷原子钟中冷原子数损失的其他机制。同时，分析了真空背景中残余气体的主要成分，对之后的真空设计也具有指导意义。; This dissertation mainly covers the author’s work during Ph.D. study period. In this dissertation, the improvement for the prototype of the space cold atom clock and related physics experiments was completed. A frequency stabilization system of laser was constructed for space cold atom clock and it's performance was improved. The ground experiments of the space cold atom clock and research on the related physical were carried out. To improve the prototype of the 87Rb space cold atom clock, the optical system, control system, and laser frequency stabilization method were optimized. We redesigned the optical mechanical supports, redistributed the optical elements on the platform, and finally a stable laser output was obtained. A new control system was established, in which the time sequence is more easy to expand and updates. This control system meets the requirements of different experiments in the laboratory environment. Based on the improved prototype, a optical pumping method was applied on the state preparation and the Ramsey fringes were obtained. For the commercial external cavity diode laser used in the prototype of the space cold atom clock, an automatic frequency stabilization system based on the DSP technology is constructed. The lock state of the laser is evaluated in real time, and the ability of long-time running is improved. Relocking the laser in time after losing lock is realized, which meets the needs of ground experiment of the prototype. In order to further improve the performance of the stabilized laser, we analyzed the limits of the loop bandwidth in the laser frequency stabilization system. The frequency of the external cavity diode laser was directly modulated using the RF signal (20 MHz) through its high speed current modulation port. The extension of the loop bandwidth improved the suppression ability of the higher frequency noise. Using the frequency stabilization system with 20 MHz modulation frequency, the suppression of the frequency noise is more than 20 dB when the Fourier frequency is 5 kHz. The measurement result of the frequency stability also shows that the short-term stability of the stabilized laser is improved when the suppression of laser frequency noise at higher frequencies can be achieved. The ground experiments of the space cold atom clock includes three aspects: (1) considering the magnetic field in space different from the ground, the ability of the magnetic shields and automatic compensation of the magnetic field for the space cold atomic clock was verified in a periodic magnetic field which is similar as the actual one in orbit, and the corresponding feedback coefficient was determined; (2) experiments of launching cold atoms at different speeds on ground is presented. The different parameters for launching cold atoms was tested; (3) the collision between cold atoms and residual gases in vacuum was analyzed theoretically and experimentally, which is the possible reason of the cold atom number decay at slow velocity. Residual gases in the background vacuum were analyzed using a mass spectrometer. The relationship between the residual gas and the loss rate of the cold atoms due to residual gases was analyzed and studied both in theory and experiments, and in the study, two situation was considered: the loss rate of cold atoms in the magneto-optical trap and the loss rate cold atoms during the free flight. The experimental results were in good agreement with the theoretical calculations, which is helpful for further analysis on other mechanisms that lead to the loss of the number of cold atoms in the cold atomic clock. Moreover, the analysis about the main residual gases in the vacuum system is instructive for vacuum design. |
| 学科主题 | 光学工程 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/31133]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 项静峰. 空间冷原子钟相关物理与技术研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。