NSF-BSF: Irradiation Studies of Cherenkov Radiators for Use in Zero Degree Calorimeters and Reaction Plane Detectors During the High Luminosity LHC Era

在瑞士日内瓦的欧洲核物理与粒子物理实验室(CERN)的大型强子对撞机(LHC)上，重离子(通常是铅原子核)的碰撞在极高的温度下产生了小液滴的核物质。这些碰撞和那些液滴状的核物质碎片的温度模拟了大爆炸后大约一微秒的早期宇宙。在大型强子对撞机上对重离子碰撞的科学解释需要对碰撞几何形状的实验描述：碰撞中的铅原子核是完全重叠还是只有部分重叠？此外，需要通过实验确定碰撞中创建的粒子相对于碰撞平面的方向。这些信息可以通过位于LHC加速器隧道中的反应平面探测器(RPD)测量到单个铅-铅碰撞的信息，这些探测器将暴露在极高的辐射剂量下。目前用于RPD有源组件的技术无法承受LHC升级所产生的辐射水平，目的是为了获得更高的束流强度。该奖项支持探索能够承受大型强子对撞机辐射水平增加的新材料。这项研究将研究先进的熔融二氧化硅材料在极高辐射水平下的行为。这项工作将包括材料研究以及RPD探测器原型的设计、建造和束流测试。该奖项将为高光度大型强子对撞机时代的ATLAS和CMS实验开发新的辐射硬反应平面探测器RPD。探测器将与零度量热计(ZDC)一起使用，以表征重离子碰撞中的事件几何结构。CMS目前的RPD对即将到来的高亮度LHC操作的辐射容忍度不够，而ATLAS目前没有RPD。新的RPD设计必须与2024年为大型强子对撞机隧道计划的修改相兼容，这将大大减少探测器可用的横向空间。基本问题是设计一种坚固的二维切伦科夫光探测器，这种探测器的辐射强度达到了前所未有的程度。与伊利诺伊大学弗雷德里克·塞茨材料研究实验室的光产生和传输测量测试同步进行的，将是在索雷克核研究中心使用中子和伽马源对每个探测器组件进行全面的辐射测试。这些数据将指导原型的建造，这些原型将在梁测试中进行检查。该项目最终将为ATLAS和CMS的ZDC集成一个最终的抗辐射RPD设计。随着在ATLAS和CMS上安装RPD，将有可能通过测量旁观中子的相关偏转来确定个别重碰撞的反应面角。测量的反应平面将使研究重离子碰撞的关键特征成为可能，从而更深入地理解夸克胶子等离子体的动力学演化。通过测量中子的初始偏转，还可以精确地表征相对于观测面的定向流动，这对初始系统的三维空间轮廓和重离子碰撞演化中的平衡前早期动力学很敏感。研发这种高度耐辐射的设备将是对高辐射环境仪器领域的重大贡献。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Collisions of heavy ions, typically lead nuclei, create small droplets of nuclear matter at extremely high temperatures at the Large Hadron Collider (LHC) of the European Laboratory for Nuclear and Particle Physics (CERN) in Geneva, Switzerland. The temperatures of those collisions and those droplet-like pieces of nuclear matter mimic the early Universe about one microsecond after the Big Bang. The scientific interpretation of heavy ion collisions at the LHC requires the experimental characterization of the geometry of the collisions: Do the colliding lead nuclei fully overlap or only partially during the collision? In addition, the orientation of the particles created in the collision with regard to the collision plane needs to be determined experimentally. This information can be measured for individual lead-lead collisions by Reaction Plane Detectors (RPDs) that will be located in the LHC accelerator tunnel and will be exposed to extremely high radiation doses. Current technology used for the active components of RPDs cannot withstand the radiation levels that will result from LHC upgrades aiming at higher beam intensities. This award supports the exploration of new materials that can withstand the increased radiation levels at the LHC. The research will study the behavior of advanced fused silica materials under extremely high radiation levels. The work will consist of material studies as well as the design, construction, and beam tests of RPD detector prototypes. This award will develop new radiation hard Reaction Plane Detectors, RPDs, for the ATLAS and CMS experiments in the High Luminosity LHC era. The detectors will be used together with the Zero Degree Calorimeters (ZDC) to characterize the event geometry in Heavy Ion collisions. The current RPD in CMS is not sufficiently tolerant of radiation for the upcoming high luminosity LHC operations, while ATLAS currently does not have an RPD. The new RPD design will have to be compatible with the modifications planned for the LHC tunnels in 2024, which will reduce considerably the transverse space available to the detector. The basic problem is devising a robust two-dimensional Cherenkov light detector that is radiation hard to an unprecedented degree. A comprehensive regimen of radiation testing of each detector component using neutron and gamma sources at the Soreq Nuclear Research Center will proceed in parallel with tests of light production and transmission measurements at the Frederick Seitz Materials Research Laboratory at the University of Illinois. These data will guide the construction of prototypes that will be checked in beam tests. The project will culminate with a final radiation hard RPD design integrated into the ZDC for both ATLAS and CMS. With the installation of an RPD in both ATLAS and CMS it will be possible to determine the reaction plane angle of individual heavy collisions by measuring the correlated deflection of spectator neutrons. A measured reaction plane will enable studies of key features of heavy ion collisions pertinent to a deeper understanding of the dynamical evolution of the Quark Gluon Plasma. By measuring the initial deflection of the neutrons, it will also be possible to characterize with precision the directed flow relative to the spectator plane, which is sensitive to the three-dimensional spatial profile of the initial system and the pre-equilibrium early time dynamics in the evolution of the heavy ion collision. The R&D to produce such a highly radiation-tolerant device will be a significant contribution to the field of instrumentation in high radiation environments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.