UK participation in the pre-production phase of CTA extension 2021

宇宙充满了能量如此巨大的粒子，它们以非常接近光速的速度运动。它们以多种方式影响宇宙，影响恒星的生命周期和星系的演化。这些粒子很难追踪，但可以通过产生伽马射线来揭示它们的存在。像它们的低能表亲X射线和伽马射线一样，它们不会穿透地球大气层，通常使用卫星望远镜来探测它们。然而，在非常高的能量（VHE）下，伽马射线非常少，以至于使用航天器探测它们变得不可能。幸运的是，通过它们在大气中相互作用时产生的蓝光，切伦科夫辐射，可以从地面观察到它们。大气中切伦科夫辐射发出的辉光比星光暗10,000倍，因此需要大镜子来收集它，而且由于闪光持续时间只有十亿分之几秒，因此需要超高速相机来记录它们。我们从目前的地基伽马射线望远镜（如HESS）中了解到，有大量的现象需要研究。VHE伽马射线望远镜已经探测到超新星爆炸、双星星星系统、遥远星系中黑洞产生的高能喷流、星星形成区和许多其他物体的残骸。这些观测不仅可以帮助我们了解这些物体内部发生了什么，还可以回答与暗物质和时空本身的性质有关的基本物理问题。然而，我们已经达到了现有仪器所能做的极限，因此来自世界各地31个国家的1640多名科学家和工程师聚集在一起建造了一个新的仪器-切伦科夫望远镜阵列（CTA）。CTA将提供比现有仪器更高的灵敏度，并将观测到的伽马射线的能量范围扩展到更低和更高的值。据预测，已知的VHE发射物体的目录将从现在已知的大约200个扩展到1000多个，我们可以期待在天体物理学和基础物理学的关键领域有许多新的发现。为了实现CTA的能量覆盖，需要三种不同尺寸的望远镜：小型（直径约4米），中型（12米）和大型（23米）望远镜（分别为SST，MST和LST）。CTA将在北方和南半球拥有阵列。这两个阵列将包括LST和MST，SST将只位于南部，因为它们被设计用于研究最高能量的现象，这些现象主要在南部天空可见。我们预计CTA南部站点的第一批望远镜将于2022年开始建造。目前有12所英国大学和实验室参与CTA。开发硬件的四个英国小组正在集中精力建造SST，我们以前开发了紧凑型高能相机（CHEC）。中国港湾工程有限公司和意大利应科院的望远镜结构从三个竞争的SST设计中被选中，作为最终SST设计的基础。在2021年的资助期内，我们将借鉴CHEC的经验，为SST设计最终的生产就绪相机。我们还将准备AIV设施，为生产做准备。我们将扩大外展活动，包括天文馆展览和英国科学会议，并加强项目管理和产品保证，以便生产。

The Universe is full of particles with energies so great that they are travelling at very close to the speed of light. They affect the Universe in many ways, influencing the life cycles of stars and the evolution of galaxies. These particles are hard to trace but can reveal their presence by producing gamma rays. Like their lower-energy cousins, X-rays, gamma rays do not penetrate the Earth's atmosphere and usually satellite-based telescopes are used to detect them. However, at very high energies (VHE) there are so few gamma rays that detecting them using spacecraft becomes impossible. Luckily, it is possible to observe them from the ground via the flashes of blue light, Cherenkov radiation, produced when they interact in the atmosphere. The glow from Cherenkov radiation in the atmosphere is 10,000 times fainter than starlight, so large mirrors are required to collect it, and because the flashes last only a few billionths of a second, ultra-fast cameras are needed to record them. We know from current ground-based gamma-ray telescopes such as HESS that there is a wealth of phenomena to be studied. VHE gamma ray telescopes have detected the remains of supernova explosions, binary star systems, highly energetic jets produced by black holes in distant galaxies, star formation regions, and many other objects. These observations can help us to understand not only what is going on inside these objects, but also answer fundamental physics questions relating to the nature of Dark Matter and of space-time itself. However, we have reached the limit of what can be done with current instruments, and so over 1640 scientists and engineers from 31 countries around the world have come together to build a new instrument - the Cherenkov Telescope Array (CTA).CTA will offer a dramatic increase in sensitivity over current instruments and extend the energy range of the gamma rays observed to both lower and higher values. It is predicted that the catalogue of known VHE emitting objects will expand from the roughly 200 known now to over 1000, and we can expect many new discoveries in key areas of astrophysics and fundamental physics. To achieve the energy coverage of CTA, telescopes of three different sizes are needed: Small (~4 m diameter), Medium (12 m) and Large (23 m) Sized Telescopes (SSTs, MSTs and LSTs, respectively). CTA will have arrays in the northern and southern hemispheres. Both arrays will include LSTs and MSTs, and the SSTs will be situated only in the souths as these are designed to investigate the highest energy phenomena, which are visible mainlyin the southern sky. We expect construction of the first telescopes on the CTA southern site to begin in 2022.There are currently 12 UK universities and Laboratories involved in CTA. The four UK groups developing the hardware are concentrating their efforts on the construction of the SSTs for which we previously developed the Compact High Energy Camera (CHEC). CHEC was selected along with the Italian ASTRI telescope structure, from the three competing SST designs, as the basis for the final SST design. During the 2021 funding period we will use the lessons learned from CHEC to design the final production-ready cameras for SST. We will also prepare AIV facilities in preparation for production. We will expand outreach activities to include a planetarium show and UK science meeting and enhance project management and product assurance in readiness for production.