Beam-Beam Tracking Studies and Luminosity Optimzation for the High-Luminosity LHC Project

TRIUMF-CERN在大型强子对撞机(HL-LHC)高光度升级方面的合作 重点研究了束-束相互作用及其对光束质量和最大值的影响 可实现的光度。 接下来将描述由欧洲核子研究组织制定并在 TRIUMF-CERN 2016年谅解备忘录。下面的大多数项目都处于非常高级的阶段，有几个结果 据报道。 使用对LHC环周围质子的长期(数百万圈)跟踪来估计动力学 光圈(DA)--稳定粒子轨迹的区域。最大亮度是一个主要特征 任何对撞机。它定义在最高能量和存在束-束碰撞的情况下，即当两个 碰撞光束在几个相互作用点(IP)附近相遇，例如阿特拉斯和CMS 大型强子对撞机。在跟踪中，通常应用弱-强模型，其中假设一个波束 不变，而另一个(弱)的粒子被跟踪以计算DA。多巴胺的部分降解 这是因为这些弱束粒子受到强束的场的偏转， 无论是在IP上遍历其核心时，还是在数百次不可避免的“远程”遭遇时。 后者是限制光度的主要因素。 跟踪主要在用于分布式计算连接的BOINC-LHC六道平台上执行 全世界数以千计的电脑。访问HL-LHC数据库和两个主要计算代码， MADX和Six-Track，由CERN提供。TRIUMF在设置方面有丰富的经验 LHC点阵、作业提交、处理等。 TRIUMF将研究与当前大型强子对撞机有关的各种机器设置和参数 (机器开发)及其未来的HL增强。如：交叉角、发射度、束流 IP处的填充、圆形或平坦碰撞波束选项等。重点设置在调谐扫描(优化 在调谐空间中的工作点)，解释非线性共振，并用 新的高梯度四极子场的随机误差。目前处于原型阶段，这些是 计划在2023年左右安装。此外，两个旨在改进对撞机的新设备 对效率进行了建模：用于在IP处倾斜束流的蟹腔，以及 远程束流-束流相互作用。 我们还继续对束-束相互作用的理论方面进行研究，基于一个分析 理论上使用李代数技术来建立非线性泰勒映射。目的是解释观察到的 并得出混沌运动的早期指标。 为学生设想的科目是：学习加速器物理，重点是非线性效应和 哈密顿系统的稳定性，熟悉CERN和NBS

The TRIUMF-CERN collaboration on High-Luminosity Upgrade of the Large Hadron Collider (HL-LHC) is focused on investigations of the beam-beam interaction and it's effects on beam quality and maximum achievable luminosity. The topics for investigation are described next, as formulated by CERN and also confirmed in the TRIUMF-CERN MOU of 2016. Most items below are in a well advanced stage, with several results reported. Long-term (millions of turns) tracking of protons around the LHC ring is used to estimate the dynamic aperture (DA) -- the domain of stable particle trajectories. The maximum luminosity is a main characteristic of any collider. It is defined at top energy and in the presence of beam-beam collisions, i.e. when the two colliding beams meet each other in the vicinity of several interaction points (IP) such as Atlas and CMS in the LHC. In tracking, it is customary to apply the weak--strong model where one beam is assumed unchanged, while particles of the other (weak) are tracked to compute the DA. A partial degradation of DA takes place since these weak--beam particles suffer deflections from the fields of the strong beam, both when traversing its core at an IP, but also as hundreds of unavoidable ``long--range'' encounters. The latter are the main factor limiting luminosity. Tracking is predominantly performed on the BOINC-LHC Six-Track platform for distributed computing joining thousands of computers world-wide. Access to the HL-LHC database and two main computing codes, MadX and Six-Track, is provided by CERN. TRIUMF has an extended previous experience in setting LHC lattice, submission of jobs, processing etc. Various machine-setups and parameters are to be studied at TRIUMF, related both to present LHC (machine development) and its future HL enhancement. Such are: crossing angle, emittance, bunch population, round or flat colliding beam options at the IP etc. Emphasis is set on tune-scans (optimization of the working point in tune space), explanation of nonlinear resonances and modeling the machine with random errors in the field of the new high-gradient quadrupoles. Currently at prototype stage, these are planned for installation in or around 2023. In addition, two novel devices intended to improve collider efficiency are modeled: crab cavities for tilting the bunch at the IP, and "wire compensation" of the long--range beam--beam interactions. We also continue our studies on theoretical aspects of the beam-beam interaction based on an analytic theory using Lie-algebraic techniques to build the nonlinear Taylor map. The goal to explain the observed resonances and derive early indicators of chaotic motion. Subjects envisaged for a student are: learning accelerator physics with emphasis on nonlinear effects and stability of Hamiltonian systems, becoming familiar with CERN&nbs