The world's deepest underground laboratory has made important progress!

Wang Jing, Wang Chao, Shen Qiushi, Science and Technology Daily Intern Reporter Li Zhaoyu

The reporter learned on August 31 that the world's largest polyethylene shielding cabin in the Jinping Underground Laboratory Phase II project has been completed, and the laboratory cabin has entered the clean laboratory construction stage.

Jinping Underground Laboratory is the first dark matter laboratory in my country and the deepest, largest and best-equipped underground laboratory in the world. It is located in the Jinping Mountain Tunnel 2,400 meters underground in Liangshan Prefecture, Sichuan. This location can use the thick rock layer of the mountain to block the interference of cosmic rays, creating a unique environment for laboratory construction.

The project tunnel wall has completed waterproof and radon suppression construction. Photo provided by the interviewee

In order to serve high-level cutting-edge physics experiments and ensure the accuracy of laboratory construction, the project construction party strives to reduce the impact on the original extremely low radiation environment of the cavern through measures such as "waterproofing and radon suppression" key technology and strict selection of low-background construction materials. "In the construction of underground laboratories, we found that these engineering measures are far from enough. A series of extremely deep underground extremely low radiation background shielding devices are also needed to achieve lower radiation background requirements. To this end, we built a large-scale combined solid shielding device-a polyethylene shielding cabin." said Tan Lei, chief engineer of Jinping Large Facility II Project of China Construction Third Engineering Bureau.

Tan Lei introduced that the polyethylene shielding cabin is 51.9 meters long, 9.78 meters wide, 7.9 meters high, and 1 meter thick. It is mainly made of 100 mm thick high-density polyethylene boards without bonding and weighs more than 1,800 tons.

The polyethylene shielding cabin project is under construction. Photo provided by the interviewee

It is understood that the background radiation value index of the cabin construction materials is high, which is a major problem in the early construction work. "The cabin is built to better shield radiation, but the materials used to build the cabin itself have radiation." Wang Wei, the project manager of the construction party, said, "The construction of the polyethylene shielding cabin is a key link in ensuring the construction of the most 'pure' laboratory. We have screened more than 60 suppliers to provide guarantees for the construction of the shielding cabin."