CERN, CH-1211 Geneva 23, Switzerland.
Cornell University, Ithaca, New York 14850, USA.
Phys Rev Lett. 2018 Aug 3;121(5):054802. doi: 10.1103/PhysRevLett.121.054802.
We report on the observation of incoherent Cherenkov radiation emitted by a 5.3 GeV positron beam circulating in the Cornell electron-positron storage ring as the beam passes in the close vicinity of the surface of a fused silica radiator (i.e., at a distance larger than 0.8 mm). The shape of the radiator was designed in order to send the Cherenkov photons towards the detector, consisting of a compact optical system equipped with an intensified camera. The optical system allows both the measurements of 2D images and angular distribution including polarization study. The corresponding light intensity has been measured as a function of the distance between the beam and the surface of the radiator and has shown a good agreement with theoretical predictions. For highly relativistic particles, a large amount of incoherent radiation is produced in a wide spectral range. A light yield of 0.8×10^{-3} photon per particle per turn has been measured at a wavelength of 600±10 nm in a 2 cm long radiator and for an impact parameter of 1 mm. This will find applications in accelerators as noninvasive beam diagnostics for both leptons and hadrons.
我们报告了在康奈尔正负电子储存环中，当 5.3GeV 的正电子束在熔凝二氧化硅辐射器表面附近（即距离大于 0.8 毫米）通过时，观察到的非相干切伦科夫辐射。辐射器的形状被设计为将切伦科夫光子发送到探测器，探测器由一个配备有增强相机的紧凑型光学系统组成。该光学系统允许同时测量二维图像和包括偏振研究在内的角分布。光强已作为光束与辐射器表面之间的距离的函数进行了测量，并与理论预测吻合良好。对于高相对论性粒子，在很宽的光谱范围内会产生大量的非相干辐射。在 2cm 长的辐射器和 1mm 的冲击参数下，在 600±10nm 的波长处测量到每转每个粒子产生 0.8×10^{-3}个光子的光产额。这将在加速器中作为用于轻子和强子的非侵入式束诊断得到应用。
