Collaborative Research: Novel Cavity Haloscopes for Axion Dark Matter at CM-Wavelengths

天文观测已经证实，宇宙基本上是“暗的”，大约85%的物质由未知的粒子组成。揭示这种暗物质的本质将对宇宙学、天体物理学和粒子物理学产生深远的影响。量子色动力学(QCD)轴子出现在粒子物理标准模型的扩展中，该模型将同时解决暗物质的奥秘和长期存在的强电荷宇称问题。该奖项支持斯坦福大学和华盛顿大学的研究人员开发一种名为光晕的新型轴子探测器，该探测器将在4-7 GHz的频率下将轴子暗物质实验的扫描速度提高三个数量级以上。获奖活动包括通过教师暑期研究计划进行外展和教育，以及为研究生提供本科生研究人员培训指导计划。在大约4 GHz的频率以上，对应于几十微电子伏特的轴子粒子质量，电流测量与理论基准之间存在着很大的灵敏度差距。提高在这些频率下的扫描速度对于扩大轴子搜索实验的覆盖范围至关重要。新的光晕设计的巨大增益是通过实现空间填充的薄壳腔来实现的，该腔将谐振器的体积与其谐振频率解耦。将在现有的250mK实验台上制造和安装一个全尺寸的科学级腔体，以展示在低温条件下的可调性和高品质因数。这些腔还将与一个基于约瑟夫森结的放大器和一个数字转换器集成在一起，以获得搜索暗光子的新的排除限制。这些进展为未来涉及大容量螺线管磁体系统的Axion搜索奠定了关键准备，就像目前用于ADMX项目的系统一样。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Astronomical observations have established that the Universe is primarily “dark” with approximately 85% of the matter made of yet unknown particles. Uncovering the nature of this dark matter will have far reaching consequences in cosmology, astrophysics and particle physics. The quantum chromodynamic (QCD) axion arises in an extension of the Standard Model of particle physics that would simultaneously solve the mystery of dark matter and the long-standing strong charge-parity problem. This award supports researchers at Stanford University and the University of Washington in the development of a novel axion detector called a haloscope that will improve the scan rate of axion dark matter experiments by more than three orders of magnitude at frequencies between 4 – 7 GHz. The awarded activities include outreach and education via a Summer Research Program for Teachers, and a mentorship program for graduate students in the training of undergraduate researchers. Above frequencies of approximately 4 GHz , corresponding to an axion particle mass of a few tens of micro-electronvolts, there exists a large sensitivity gap between current measurements and the theoretical benchmarks. Improving the scan rate at these frequencies is crucial to enhancing the reach of axion search experiments. The large gain of the new haloscope design is achieved by implementing a space-filling thin-shell cavity that decouples the resonator’s volume from its resonant frequency. A full-sized science-grade cavity will be fabricated and installed in an existing 250mK testbed to demonstrate tunability and high quality factor under cryogenic conditions. The cavities will also be integrated with a Josephson Junction-based amplifier and a digitizer to obtain new exclusion limits on searches for dark photons. These developments establish key preparations for future axion searches involving large-volume solenoid magnet systems like those currently utilized for the ADMX project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.