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Search for dark matter axions

寻找暗物质轴子

基本信息

批准号：
09102010
负责人：
MATSUKI Seishi
金额：
$ 184.96万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Specially Promoted Research
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09102010/
关键词：
The Universe Dark matter Axion Rydberg atoms Microwave resonant cavity Dilution refrigerator Field ionization Universe Dark Matter Microwave detection Microwave cavity 超高感度マイクロ波検出ダ-クマタ-ダ-クハロ-超高密度マイクロ波検出

项目摘要

Search for dark matter axions over the mass range of 11 μeV is in progress with Rydberg atoms in a resonant cavity at low temperature. Along with the search, efforts have been devoted to improve the detection efficiency by modifying a number of parts of the experimental apparatus. Specifically the following improvements were obtained for increasing the detection efficiency: 1) Reduction of the stray electric field around the cavity and the field ionization detector regions, 2) Reduction of the motional Stark effect on the broadening of the resonant width for the Rydberg states in a cavity by eliminating the magnetic field in the region of the cavity and the detector. In addition the effect of the collisions between the Rydberg atoms and the ground state Rb atoms on the selective field ionization performance was carefully examined to improve the selectivity. For these improvements, further cleaning of the inside of the cavity and of the detector system were carefully tried and shielding of the magnetic field around the field ionization detection region was especially improved by incorporating a number of sheets made of NbTi-Nb-Cu complex. Also we improved the pulsed field ionization performance to get better detection efficiency.We also somewhat modified the structure of metal post system in the cavity to get more uniform electric field mode in the cavity, thus improving the detection efficiency. Installing a sextupole magnet to increase the intensity of the atomic beam and to select and polarize the atomic hyperfine state was also examined to increase the overall detection efficiencies. With these efforts, the overall detection efficiency was increased and these improvements enabled us to shorten the necessary time to search for axions. No axion signals have been definitely observed at the mass region investigated.

在低温共振腔中使用里德伯原子寻找11 μeV质量范围内的暗物质轴子正在进行中。沿着该研究，人们致力于通过修改实验装置的多个部分来提高检测效率。具体地说，为了提高探测效率，获得了以下改进：1）减少了腔和场电离探测器区域周围的杂散电场，2）通过消除腔和探测器区域中的磁场，减少了运动斯塔克效应对腔中里德伯态共振宽度加宽的影响。此外，为了提高选择性，还研究了里德伯原子与基态Rb原子碰撞对选择性场电离性能的影响。对于这些改进，仔细地尝试了腔的内部和检测器系统的进一步清洁，并且通过结合由NbTi-Nb-Cu络合物制成的多个片来特别地改进场电离检测区域周围的磁场的屏蔽。改进了脉冲场电离性能，提高了探测效率，并对腔体内金属柱系统的结构进行了一定的改进，使腔体内的电场模式更加均匀，从而提高了探测效率。安装一个六极磁铁，以增加原子束的强度，并选择和消除原子的超精细状态，也被检查，以提高整体检测效率。通过这些努力，提高了整体检测效率，这些改进使我们能够缩短搜索轴子所需的时间。在所研究的质量区没有明确观察到轴子信号。