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子与粒子物理实验室（CERN）的大型强子对撞机（LHC）中，重离子（通常是铅核）的碰撞在极高的温度下产生核物质的小液滴。这些碰撞和核物质的水滴状碎片的温度模拟了大爆炸后大约一微秒的早期宇宙。对大型强子对撞机中重离子碰撞的科学解释需要对碰撞的几何形状进行实验表征：碰撞的铅核在碰撞过程中是完全重叠还是部分重叠？此外，在碰撞中产生的粒子相对于碰撞平面的方向需要通过实验来确定。这些信息可以通过放置在大型强子对撞机加速器隧道中的反应平面探测器（rpd）来测量，该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针对更高光束强度升级所产生的辐射水平。该奖项支持探索能够承受大型强子对撞机增加的辐射水平的新材料。该研究将研究高级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、建造和光束测试。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形状。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目前还没有RPD。新的RPD设计必须与2024年LHC隧道的修改计划相兼容，这将大大减少探测器可用的横向空间。基本的问题是设计一个坚固的二维切伦科夫光探测器，它的辐射强度达到了前所未有的程度。在Soreq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，同时在伊利诺伊大学弗雷德里克塞茨材料研究实验室进行光产生和透射测量测试。这些数据将指导原型的构建，原型将在梁测试中进行检查。该项目将以最终的辐射硬RPD设计集成到ATLAS和CMS的ZDC中达到高潮。通过在ATLAS和CMS中安装RPD，可以通过测量旁观中子的相关偏转来确定单个重碰撞的反应面角。测量的反应平面将使重离子碰撞的关键特征的研究相关的夸克胶子等离子体的动力学演化的更深层次的理解。通过测量中子的初始偏转，还可以精确地表征相对于观看面的定向流，这对初始系统的三维空间轮廓和重离子碰撞演化中的预平衡早期动力学非常敏感。研发生产这种高耐辐射器件将对高辐射环境下的仪器仪表领域做出重大贡献。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.