Trapped ion clock with enhanced reliability (TICKER)

“增强可靠性的囚禁离子钟”项目(TICKER)汇集了计量级离子陷阱开发、超稳定室温腔稳定激光器和激光源开发方面的世界领先专业知识，在现场部署的最先进的光学钟中提供前所未有的性能。光学原子钟(OAC)在过去几十年中取得了非凡的改进，代表了精密测量技术的顶峰。OAC的极高精度为探测暗物质、相对论大地测量学和提高卫星导航精度的基础物理和技术带来了令人兴奋的新机会。然而，当代光学原子钟对更广泛的技术和工业基础的科学和技术影响有限，因为它们是脆弱的、实验室大小的复杂系统，由熟练的科学家在受控良好的环境中操作。这些限制意味着世界范围内只有几个可操作的例子，仅限于国家计量研究所(NMI)，如NPL。要释放OAC的变革潜力，它们必须变得更简单、更强大。这不是简单地缩小实验室时钟就能实现的；我们需要新的方法和技术。我们将开发绕过这些限制的技术，并允许创造实用的光学时钟，重点关注单电离的锶-88(锶+)系统作为最可行的候选者。在这个项目中，我们将开发可制造的计量级离子陷阱，这些陷阱足够坚固，可以在控制较差的偏远地点和移动平台上运行，开发可移动的环境不敏感光学参考腔，以及用作低功率和坚固的激光冷却离子的422 nm DFB激光器。与另一类主要的高性能时钟-中性原子晶格钟相比，基于俘获离子的原子钟本质上更简单，运行所需的功率也更低。离子钟也放宽了对时钟激光器的要求，使其更适合嘈杂的环境。捕获和激光冷却单个离子只需要不到1瓦的射频功率和不到1毫瓦的光功率；电极结构和真空系统可以使用现有的技术在有限元分析的辅助下进行小型化和加固。锶+系统特别有吸引力，因为时钟转换可以用一种提供中心频率对环境低灵敏度的方式来测量。此外，其简单能级结构中的跃迁主要可以用商品激光器来解决。一个例外是422 nm激光冷却过渡。目前，这种光必须由振动敏感的ECDL激光器或来自红外DFB激光器的低效倍频产生。一台422 nm的DFB激光器将使交换和坚固性得到极大的提高。NPL获得专利的立方腔设计是领先的可运输和力不敏感设计，将被改装以适应可场部署原子钟的要求。将立方腔间隔的体积从125cc减少到27cc仍然提供了良好的频率稳定性，同时大大降低了所需的环境屏蔽。此外，我们还发明了一种新技术，利用材料的各向异性来进一步减少对环境的影响，这将在力和振动不敏感的设计的同时扩展温度不敏感。随着光学频率梳的增加(在许多其他计划下PACE正在开发，以满足光学时钟的要求)，我们共同解决了阻碍光学时钟在现场部署应用的主要挑战。

The 'trapped ion clock with enhanced reliability' project (TICKER) brings together world leading expertise in metrological-grade ion trap development, ultrastable room-temperature cavity-stabilised lasers, and laser source development to deliver unprecedented performance in a field-deployed state-of-the-art optical clock.Optical atomic clocks (OACs) have made extraordinary improvements over the last few decades and represent the pinnacle of precision measurement technology. The extreme accuracy of OACs enables exciting new opportunities for both fundamental physics and technology from detecting dark matter, relativistic geodesy, and improving satellite navigation accuracy. However, the science and technology impact from the current generation optical atomic clocks has been limited for the wider technology and industry base as they are fragile and complex laboratory-sized systems operated in well-controlled environments by skilled scientists. These limitations mean that only a handful of operational examples exist worldwide, restricted to National Metrology Institutes (NMIs) such as NPL. To unlock the transformative potential from OACs they must become simpler and more robust. This cannot be achieved by simply shrinking a laboratory clock; new approaches and technologies are called for.We will develop the technologies that bypass these constraints and allow the creation of practical optical clocks, focusing on the singly ionised strontium-88 (Sr+) system as the most viable candidate. Within this project we will develop metrological-grade ion traps that are manufacturable and robust enough to operate in less-well-controlled remote locations and mobile platforms, a transportable environmentally insensitive optical reference cavity, and a 422-nm DFB laser as a low-power and robust source for laser-cooling the ion. Atomic clocks based on trapped ions are inherently simpler and require lower power to operate than the other major class of high-performance clocks - neutral atom lattice clocks. Ion clocks also have relaxed requirements of the clock-laser, making them more suitable for noisy environments. Trapping and laser cooling a single ion requires less than a watt of RF power and less than a milliwatt of optical power; the electrode structure and vacuum system can be miniaturised and ruggedised using established techniques aided by finite element analysis. The Sr+ system is particularly attractive because the clock transition can be measured in a way that provides low sensitivity of the centre frequency to the environment. Additionally, the transitions in its simple energy level structure can mostly be addressed with commodity lasers. One exception is the 422-nm laser-cooling transition. Currently this light must be produced from either a vibration sensitive ECDL laser or inefficient frequency doubling from an infrared DFB laser. A 422-nm DFB laser would enable a great improvement in the SWAP and robustness.NPL's patented cubic cavity design is the leading transportable and force insensitive design and will be adapted to suit the requirements of field-deployable atomic clocks. Reducing the volume of the cubic cavity spacer from 125 cc to 27 cc still provides good frequency stability while greatly reducing the required environmental shielding. Moreover, we have invented a novel technique that exploits material anisotropy to further reduce environmental impact, which will extend the temperature-insensitivity alongside the force- and vibration-insensitive design. Together, with the addition of an optical frequency comb (being developed at pace under many other programs, to the requirements of optical clocks) we address the major challenges that are preventing optical clocks from field deployed applications.