This article comes from WeChat public account: SELF 格致 论 道 论坛 （ID: SELFtalks） , Speaker: Cao Zhen (Researcher, Institute of High Energy Physics, Chinese Academy of Sciences)

“The high-altitude cosmic ray observation station is actually a 1.3 square kilometer sky array. This sky array was originally a very primitive uninhabited area. Why go to such a high place to build an observation station? ? “

The following is the actual record of the speech:

Hello everyone, I am Cao Zhen from the Institute of High Energy Physics. Today I want to share with you how the cutting-edge research on science is carried out on the boundary between our known world and the unknown world.

I use Experiment, Particle, Celestial, Physics to summarize this lecture. These four words are more complicated to put together, and I hope that through this lecture, you will understand that scientific research is not that complicated.

“Sky array” built in Daocheng

For example, the high-altitude cosmic ray observation station is actually a 1.3 square kilometer sky array. This sky array was originally a very primitive uninhabited area. Why go to such a high place to build an observation station? The observatory is located in the beautiful Daocheng, 4410 meters above sea level,

This is located on the edge of the Tibetan Plateau. The altitude of Daocheng is suitable for scientific research and is close to the edge of the roof of the world. It is closer to the developed areas and easier to do this.

Now you know that Daocheng not only has the beautiful Aden Scenic Area, but also an array of LHAASO that explores the mysteries of the universe. We are building this array here to welcome messengers carrying the secrets of the universe.

This picture is a picture drawn by a reporter from the British “Nature” magazine and I went back to draw a picture myself. I feel very amazing. He actually understood it so accurately and described our array very clearly.

LHAASO in the eyes of a journalist of British “Nature” magazine in order to welcome the “messenger” who carries the secret of the universe

This array has 4 main detectors , and researchers have arranged it into arrays of various shapes, waiting for the cosmic rays to reach Earth from the sky.

In fact, the array is ready to meet a “rain”. This rain is not a droplet, but a particle, and the rain lasts for a very short time, only a few nanoseconds. We arranged the detectors just to welcome them.

This picture shows me just nowIn this process, when the “rain” fell on the array, the detectors that were hit by the particles “fired”, and the time was recorded as soon as the “fire”, the distance of each detector is already Knowing, we can use it to reverse the direction in which the particles of the cosmic rays reach.

If cosmic ray particles can be pushed back to find a source, they can guide scientists to find the celestial body they want to observe.

The four detectors in the array are: Electromagnetic particle detectors, muon detectors, water Cherenkov detectors, and wide-angle Cherenkov telescope arrays.

The following is the current construction of the array. You can see that a clearer array has been formed. The size of this array is only 1/4 of the entire array. There is a very large pool under the bright metal roof in the middle. This pool has an area of ​​300 meters by 300 meters and a water depth of 5 meters. Water is used as the detection medium.

One square kilometer array: 1/4 will be put into operation < / p>

The following figures show an array of more than 30 detectors and their measured cosmic ray results.

Using this array, we have received more than 100 million cosmic ray particles in more than half a year. The results of observation and measurement are very good, and some of the goals of the original design were fully achieved. The entire 1/4 array should be ready for observation at the end of this month.

The large pool in the middle consists of three parts, one of which