UK Participation in the CTA pre-production phase

宇宙充满了能量如此之高的粒子，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。大气层中切伦科夫辐射发出的辉光比星光暗一万倍，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HESS等现有的地面伽马射线望远镜中了解到，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29个国家的大约1000名科学家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130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。北方阵列将由4个LST和25个MST组成。南部阵列将在其4个LST和25个MST的基础上增加70个SST的广泛阵列，以研究主要在南部天空可见的最高能量现象。我们预计CTA南部站点的第一批望远镜将于2017年开始建造。目前有12所英国大学和实验室参与CTA。英国的团体正集中力量建造SST。我们已经制作了一个创新的双镜SST设计，伽马射线切伦科夫望远镜（GCT），这是在巴黎埃菲尔铁塔的视线原型，并正在建立两个原型相机，不同的传感器，我们将在这个设备上进行测试。在这里，我们要求找到完成这些摄像机的测试，使用结果来设计GCT的最终摄像机，并与国际合作伙伴一起建造其中三个，安装在CTA南部场地的GCT上。我们还希望与英国工业界合作，为望远镜提供比目前设计更好、更便宜的反射镜，并改进GCT结构的各个方面。最后，我们希望为CTA开发数据分析技术，以确保英国科学家在第一批望远镜开始运行时就准备好分析CTA的数据。

The Universe is full of particles with energies so high 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 about 1000 scientists from 29 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 130 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. The northern array will consist of 4 LSTs and 25 MSTs. The southern array will add to its 4 LSTs and 25 MSTs an extensive array of 70 SSTs, to investigate the highest energy phenomena, visible mainly in the southern sky. We expect construction of the first telescopes on the CTA southern site to start in 2017.There are currently 12 UK universities and Laboratories involved in CTA. The UK groups are concentrating their efforts on the construction of the SSTs. We have produced an innovative dual-mirror SST design, the Gamma-ray Cherenkov Telescope (GCT), which is being prototyped in sight of the Eiffel Tower in Paris, and are building two prototype cameras, with different sensors, we will test on this device. Here we ask for finding to complete tests of these cameras, use the results to design the final camera for the GCT and to build, with international partners, three of these for installation on GCTs on the CTA southern site. We also want to work with UK industry to provide mirrors for the telescope that are better and cheaper than current designs, as well as improving aspects of the GCT structure. Finally, we want to develop data analysis techniques for CTA, to ensure that UK scientists are ready to analyse the data from CTA as soon as the first telescopes start operation.