Cosmic particles probe ancient archeological site

In 2020 a monsoon in central China triggered the collapse of a section of the 600-year-old Mingqin Mansion City Wall in the city of Xi’an, causing injury to four pedestrians and damage to nearby vehicles. With hundreds of known cracks, Xi’an’s ancient defensive wall is at serious risk of further damage. However, external observations are insufficient for evaluating the internal structure and more intrusive methods are incompatible with cultural preservation.

Liu et al. used muography to probe the structure of the wall as a case study in archaeogeophysics. The muography technique employs cosmic ray muons from space to image the interior of large structures from a distance.

Cosmic ray muons are created as high-energy cosmic ray particles collide with particles in the upper atmosphere and are constantly raining on the Earth’s surface. The particles can pass through most matter, but do so at lower rates in high density regions, allowing them to be used to create a picture of an object’s internals.

“Worldwide, there are a huge number of historical and valuable cultural relics and monuments that haven’t been excavated,” said author Zhiyi Liu. “Muography offers an environmentally friendly and high-resolution option.”

In collaboration with the Xi’an City Wall Management Committee, the researchers used muon sensors to create a three-dimensional density image. They paired that with a method to remove noise from the images and evaluate their uncertainty.

Their results demonstrated the feasibility of using muography to survey large-scale archeological sites at high enough resolution to aid in preservation efforts. The researchers plan to improve their sensors and data analysis software to aid other archaeological sites around China.

Source: “High-precision muography in archaeogeophysics: A case study on Xi’an defensive walls,” by Guorui Liu, Xujia Luo, Heng Tian, Kaiqiang Yao, Feiyun Niu, Long Jin, Jinlei Gao, Jian Rong, Zhiqiang Fu, Youxin Kang, Yuanyong Fu, Chun Wu, Heng Gao, Jiangbo Gong, Weixiong Zhang, Xiaogang Luo, Chunxian Liu, Xiangsheng Tian, Minghai Yu, Feng Wu, Jingjing Chen, Juntao Liu, and Zhiyi Liu, Journal of Applied Physics (2023). The article can be accessed at https://doi.org/10.1063/5.0123337 .

This paper is part of the Special Collection Recognizing Women in Applied Physics Collection, learn more here .