On August 26th, the Jiangmen Underground Neutrino Observatory (JUNO) successfully completed the filling of 20,000 tons of liquid scintillator and officially began data collection. After more than a decade of preparation and construction, JUNO has become the world's first operational large-scale and high-precision scientific facility dedicated to neutrino research. Initial test run data show that its key performance indicators have fully met or even exceeded expectations.

Located 700 meters underground in Jiangmen, Guangdong, the detector is able to detect neutrinos from the Taishan and Yangjiang Nuclear Power Plants 53 kilometers away, and measure their energy spectrum with extremely high precision. At its core is a central detector filled with 20,000 tons of liquid scintillator, positioned at the center of a water pool inside the underground experimental hall. It is supported by a 41.1-meter-diameter stainless steel mesh shell and equipped with an acrylic sphere and nearly 45,000 photomultiplier tubes, enabling research through the scintillation light produced when neutrinos interact with the liquid scintillator.

Compared with similar international experiments, JUNO's determination of the mass ordering of neutrinos is free from interference caused by the earth matter effect. It will also significantly improve the precision of the three neutrino oscillation parameters. In the future, it may help resolve major particle physics questions such as mass ordering of neutrinos, while also advancing frontier research on solar and supernova neutrinos.

Led by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS), the experiment involves nearly 700 scientists from 74 research institutions across 17 countries. With a designed lifespan of 30 years, JUNO can later be upgraded into the world's most sensitive neutrinoless double-beta decay experiment, in order to probe the absolute mass of neutrinos and test whether they are Majorana particles. This will drive progress in particle physics, astrophysics, and related fields. According to the JUNO collaboration's spokesperson, this marks a breakthrough that will help answer fundamental questions about matter and the nature of the universe.

江门中微子实验完成2万吨液闪灌注 正式运行取数

8月26日，江门中微子实验（JUNO）成功完成2万吨液体闪烁体灌注并正式运行取数。历经十余年筹备建设，该实验成为国际首个运行的超大规模、超高精度中微子专用大科学装置，试运行首批数据显示其关键性能指标全面达标或超预期。

该探测器位于广东江门地下700米处，可探测53公里外台山、阳江核电站的中微子，以超高精度测量其能谱。核心为2万吨液体闪烁体中心探测器，置于地下实验大厅水池中央，由直径41.1米不锈钢网壳支撑，搭载有机玻璃球、近4.5万只光电倍增管等关键部件，通过探测中微子与液闪作用的闪烁光开展研究。

相较于国际同类实验，其测定中微子质量排序不受地球物质效应等干扰，还将显著提升3个中微子振荡参数精度，未来可解决中微子质量排序等粒子物理重大问题，并助力太阳、超新星等中微子前沿研究。

该实验由中科院高能所主导，17国74家科研机构近700人参与，设计寿命30年，后期可升级为世界最灵敏无中微子双贝塔衰变实验，以探测中微子绝对质量、检验其是否为马约拉纳粒子，推动粒子物理、天体物理等领域发展。合作组发言人表示，此举是突破性进展，将助力解答物质与宇宙本质的基本问题。

翻译 | 曾敏
审校 | 林佳岱