Design and performance of the Fast Beam Condition Monitor for luminosity and background measurement at the CMS Experiment in LHC Run 3
The CMS BRIL Collaboration, Eliana Acurio, Ying An, Iakov Andreev, Tomas Atehortua, Georg Auzinger, Hamed Bakhshiansohi, Gergely Balint, Luis Ignacio Banos, Juan Pedro Barajas Ibarria, Hugo Alberto Becerril, Jose Feliciano Benitez, Philip H. Butler, Alan Campbell, Edgar Fernando Carrera Jarrın, Alfredo Castaneda Hernandez, Marco Costa, Antonio Cota Rodriguez, Luis Enrique Cuevas Picos, Anne Dabrowski, Vladyslav Danilov, Andres Guillermo Delannoy Sotomayor, Hedwin Aaron Encinas Acosta, Krisztian Farkas, Anna Feherkuti, Mahmoud Moussa Abdelkhalek Gadallah, Luis Gabriel Gallegos Marinez, Angela Giraldi, Alfredo Gurrola, Moritz Guthoff, Mykyta Haranko, Maria Hempel, Hans Henschel, Shilpi Jain, Armin Kadlecsik, Jan Kaplon, Adam Kardos, Olena Karacheban, Nimmitha Karunarathna, Joscha Ahauser, Georgios Krintiras, Leen Lambers, Jessica Leonard, Moises David Leon Coello, Maksim Jenihhin, Willard Johns, Markus Klute, Wolfgang Lange, Kuan-Yu Lin, Wei Heng Liu, Wolfgang Lohnmann, Arkady Lokhovitskiy, Robert Loos, Peter Major, Sophie Mallows, Jeremiah Mans, Daniel Marlow, Badder Marzocchi, John-Erik Meißner, Philip Jason Meltzer, Stefano Mersi, Andreas Bernhard Meyer, Dmitri Mihhailov, Valeria Monti, Michele Mormile, Javier Alberto Murillo Quijada, Vlodymyr Myronenko, Cristina Oropeza Barrera, Younes Otarid, Christopher Palmer, Jose David Ochoa Flores, Michelangelo Pari, Gabriella Pasztor, Marek Penno, Fabio Lucas Pereira Carneiro, Elena Popova, Attila Jozsef Radl, Evan Altair Ranken, Beatriz Ribeiro-Lopes, Francesco Romeo, Carlos Romero, Jonas Rubenach, Alexander Ruede, Vladimir Ryjov, Santeri Saariokari, Alessia Saggio, Valerie Scheurer, Vahid Sedighzadeh Dalavi, Mohammad Sedghi, Tatiana Selezneva, Konstantin Sharko, Alexey Shevelev, Konstantin Shibin, Sunil Somalwar, Rafael Sosa, Stefan Spanier, David Stickland, Robert Stone, Andromachi Tsirou, Oleksii Turkot, Lizardo Valencia Palomo, Cristina Vazquez Velez, Roger Rusack, Paola Tropea, Balazs Ujvari, Mayda Velasco, Piero Giorgio Verdini, David Walter, Joanna Wanczyk, Jesus Alberto Velazquez Corral, Daniel John Wilbern, Zhen Xie, Maryam Zeinali, Wolfram Zeuner
快速束流条件监测器（BCM1F）自2008年LHC首次实现束流循环以来，便在CMS实验中投入使用。其最初作为束流感应本底监测器，用于快速束流损失探测；2012年运行期间，研究人员发现它也具备亮度测量潜力，自2015年第2轮运行（Run 2）数据采集启动以来，便作为束流辐射、仪器与亮度（BRIL）系统的一部分，被用于亮度测量。多年来，该系统经历了传感器、前端及后端电子学的多次升级，测量精度得到提升，且这些提升在LHC第3轮运行（2022-2026年）的高堆积条件下依然有效。基于Run 2期间BCM1F所有升级的经验，该探测器在LHC第3轮运行前完成了全面重建，采用交流耦合硅 pad 二极管与主动冷却技术。该最新版本探测器对瞬时亮度表现出优异的线性度，且达到纳秒级定时精度，可为亮度和本底测量提供更精确的系统修正。本文详细介绍了LHC第3轮运行所用探测器系统，包括传感器的选型与鉴定、读出系统概述，还阐述了亮度数据的处理与校准策略，探讨了运行中的障碍，并将BCM1F测量结果与CMS其他亮度测量结果进行对比，以评估其作为亮度计的性能；最后，讨论了未来拟议的高亮度LHC（HL-LHC）升级所用亮度探测器的设计方向。
英文摘要
The Fast Beam Condition Monitor (BCM1F) has been used at the CMS Experiment since the first LHC circulating beams in 2008. Originally meant as a beam-induced background monitor for fast beam losses detection, it showed a potential also for luminosity measurements in 2012 running, and has been used for luminosity measurements since the beginning of Run 2 data taking in 2015 as a part of the Beam Radiation, Instrumentation and Luminosity (BRIL) system. Over the years, the system has undergone various upgrades to the sensors, the front-end and back-end electronics, providing improvements in the precision of the measurements, that remain valid in the higher pileup conditions of LHC Run 3 (2022-2026). Based on the experience of all BCM1F Run 2 upgrades, the detector was completely rebuilt prior to LHC Run 3 using AC-coupled silicon-pad diodes and active cooling. This latest detector version exhibits excellent linearity with instantaneous luminosity and achieves nanosecond-level timing precision, enabling improved systematic corrections for luminosity and background measurements. This paper presents a detailed overview of the detector system for LHC Run 3, including the selection and qualification of sensors as well as a summary of the readout system. It also outlines the processing and calibration strategy for luminosity data, discussing operational hurdles and comparing BCM1F measurements to other CMS luminosity measurements to assess the system's performance as a luminometer. Lastly, the implications for the design of a future luminosity detector to be used in the envisioned HL-LHC upgrade are discussed.
