发表机构
CERN（欧洲核子研究组织）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文设计并运行了CERN SPS慢引出中的3晶体多体积反射阵列，通过多保真贝叶斯优化实现四倍损失减少，并已用于物理生产，中位减少3.6倍。
AI 中文摘要
从CERN超级质子同步加速器（SPS）慢引出到北区实验的质子通量受到三次整数共振引出期间在静电切割磁铁上丢失的束流所感生放射性的限制。晶体阴影法，即利用薄弯曲硅晶体偏转原本会撞击切割磁铁丝的部分束流，自2021年起已在SPS投入运行，单个非局部位置晶体将引出损失减半，但尚未达到未来高强度运行活化预算所要求的四倍减少。本文介绍了在第四长直线节（LSS4）非局部位置部署的3晶体多体积反射阵列（MVRA）的设计、部署与运行。阵列几何结构通过多保真贝叶斯优化（MFBO）设计，结合多层感知器代理模型与全粒子跟踪，预测三晶体可实现四倍损失减少，理想对齐的四至五晶体阵列可实现高达十倍的减少。束流测量证实了预测：在最优状态下，实际建造的阵列将损失减少了预测的四倍，且与测量位置和角度扫描匹配的束流动力学模拟在几个百分点内重现了结果。该阵列此后已用于物理生产，通过极值搜索控制器维持在其运行平台，相对于预阴影基线，在10万次引出循环中损失减少中位数为3.6倍。讨论了与目标的剩余差距、当前安装的局限性以及升级至4或5晶体阵列的方案。
英文摘要
The flux of protons slow-extracted from the CERN Super Proton Synchrotron (SPS) to the North Area experiments is limited by the induced radioactivity of the beam lost on the electrostatic septum during the third-integer resonant extraction. Crystal shadowing, in which a thin bent silicon crystal deflects the portion of beam that would otherwise impinge on the septum wires, has been in operation at the SPS since 2021, and a single crystal at a non-local position halved the extraction losses, short of the fourfold reduction that the activation budget of the future high-intensity operation calls for. In this paper, the design, deployment and operation of a 3-crystal Multi-Volume Reflection Array (MVRA) at the non-local position in the fourth long straight section (LSS4) are presented. The array geometry was designed by Multi-Fidelity Bayesian Optimization (MFBO), combining a multilayer-perceptron surrogate with full particle tracking, which predicts a fourfold loss reduction with three crystals and up to tenfold with an ideally aligned array of four to five. Measurements with beam confirm the prediction: at its optimum the as-built array reduces the losses by the predicted factor of four, and beam dynamics simulations matched to the measured position and angle scans reproduce them to a few per cent. The array has since been used in physics production, held on its operating plateau by an extremum-seeking controller, with a median loss reduction by a factor of 3.6 over 0.1 million extraction cycles relative to the pre-shadowing baseline. The remaining margin to the target, the limitations of the present installation and the upgrade to a 4- or 5-crystal array are discussed.
Comments22 pages, 14 figures, 8 tables
