The superconducting Transition-Edge Sensor (TES) is a critical technology for next-generation X-ray spectrometers, known for its exceptional energy resolution. In the last decade, TESs based on AlMn alloy films have been extensively used in several cosmic microwave background (CMB) experiments. The advantages of simple fabrication process and easily tunable critical temperature make them an alternative to bilayer TESs. However, they have rarely been applied to X-ray detection until now. We developed an annular AlMn TES for X-ray detection and tested it in a dilution refrigerator with a Superconducting Quantum Interference Device (SQUID) amplifier, achieving an Full Width at Half Maximum (FWHM) of 12.1 +- 0.3 eV at 17.48 keV. To the best of our knowledge, this is the first demonstration of an AlMn TES achieving an energy resolution below 0.1%, highlighting its potential for high-resolution X-ray detection.
@article{arxiv.2602.11728,
title = {Beyond One-Thousandth Energy Resolution with an AlMn TES Detector},
author = {Liangpeng Xie and Yifei Zhang and Zhengwei Li and Zhouhui Liu and Shibo Shu and Junjie Zhou and Xufang Li and Haoyu Li and He Gao and Yudong Gu and Xuefeng Lu and Yong Zhao and Congzhan Liu},
journal= {arXiv preprint arXiv:2602.11728},
year = {2026}
}