The exciting news is the LHAASO detection of more than 530 extensive air showers generated by Ultra High Energy photons coming from the direction of 12 galactic sources . Since gamma rays propagate straight , this detection indicates the direction of the cosmic ray factories accelerating cosmic rays to one million of giga-electronvolt energies or more, the so-called PeVatrons, whose nature puzzled scientist for long time.
[ Indeed, gamma rays of such energies cannot be produced thermally, they are generated when highly relativistic cosmic rays collide with ambient gas, as, for instance, molecular clouds.]
I would like to comment the reason of the LHAASO performance .
Two aspects are relevant in this context : a challenging project and technical design and its efficient realization at high altitude requiring an adequate organization.
The LHAASO layout consists of an impressive assembly of many traditional instruments equipped with advanced technology devices . The combination of ‘brute force’ and technology at the edge of that currently available gives LHAASO an outstanding and unprecedented sensitivity to detect high-energy gamma rays.
Experimental conditions at the top of the mountain at an altitude of 4410 meters are challenging. Persons have to withstand harsh conditions often troublesome for humans. Yet setting-up experimental apparatus in remote locations can still be fraught with logistic difficulties.
I visited the LHAASO site 2 years ago. Despite the apparent remoteness , Daocheng hosts reasonable infrastructures and communications. A small village 1-hour distant by car at a lower altitude operates as a base hosting a guest-house , living and dining and working facilities . Careful planning has been critical to ensure a regular installation and operation. As a result, LHAASO is growing according to the time schedule and will be completed in this year.
LHAASO will operate continuously and steadily for many years in order to accumulate a large data set . While extending the search for PeVatrons, LHAASO will explore in depth a wide energy range where the transition from galactic to extragalactic cosmic rays is expected , a region covered by very few experiments. Many of LHAASO discoveries will no doubt bring surprises. Thus, there is a good chance that the cosmic-ray mystery could be unveiled. There are exciting times ahead.
LHAASO探测到了从12个超高能伽马源辐射而来的530多个空气簇射事例，这是一个令人兴奋的消息。 因伽马射线沿直线传播，这些事例瞄准了十几个宇宙线加速工厂的方向。 这些工厂把宇宙线加速到了1000万亿电子伏特甚至更高的能量，称为所谓的拍电子伏特加速器（英文名称：PeVatrons），其性质长期以来一直困扰着科学家。
[确实，具备如此高能量的伽马射线不可能起源于热辐射，它们是由极端相对论的宇宙线与周围气体例如分子云碰撞产生的。]
下面我对LHAASO的优良性能做一点评价。
LHAASO的成功可以归结为两个方面的原因：挑战性的工程设计，及其在高海拔地区高效地实现。这两个方面都离不开完善的组织与协调。
LHAASO阵列-由极其大量的传统探测器组成，但它们都配备了先进的技术设备。 “暴力”解决方案与尖端技术的结合，赋予了LHAASO卓越的、前所未有的高能伽马探测灵敏度。
在4410米的高山之巅开展实验极具挑战性，人们必须克服恶劣的自然条件给身体带来的许多麻烦，在偏远地区安装仪器设备还存在着许多后勤方面的困难。
两年前我访问了LHAAO站址。尽管距离遥远，稻城却拥有不错的基础设施和通讯。在这个小城镇里运营着一个具备住宿、生活、餐饮和工作等相关设施的测控基地，距离观测站仅仅1小时车程，海拔也较低。 这些周密的考虑和安排对于确保正常的探测器安装和运行至关重要，正因为如此，LHAASO按照时间表稳步推进，将在今年内建成。
LHAASO将持续稳定运行多年，积累大量的数据。在扩大搜索PeVatron的同时，LHAASO将在宽广的能量范围内深入探索宇宙线从银河系内起源向银河系外起源的转换，这个领域其实并未开展过充分的实验研究。 LHAASO将会带来许多惊喜的发现，宇宙线起源之谜有机会被揭开，未来定会有一些激动人心的时刻。
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