The Large Hadron Collider (LHC) is affected by the electron cloud (EC) phenomenon that can provoke beam instabilities, detrimental heat loads and pressure increases in the vacuum system. An innovative dedicated system called vacuum pilot sector (VPS) provides a continuous monitoring of the electron flux and of the pressure signals thanks to electron pickup and vacuum gauges. The VPS system is installed in a room temperature, field-free part of the LHC storage ring. Several technical surfaces, such as ex situ nonevaporable getter (NEG), amorphous carbon coating and copper, are simultaneously tested. The main outcomes of this study show that the EC signals have: (1) a linear dependence upon the number of bunches and upon the bunch population in the multipacting regime, (2) a multipacting threshold at a given bunch population, (3) a reduction under beam conditioning, (4) a strong dependence on the filling pattern and beam energy. The comparison between different surfaces shows that amorphous carbon coating reduces drastically the EC buildup, thanks to its low secondary electron yield (SEY) and photoelectron yield (PY), while copper and ex situ NEG coated surfaces suffer of EC multipacting, even after several months of operation. The multipacting rate coefficients are higher for copper than for ex situ NEG, as predicted from the SEY estimation. Other detailed experimental observations are discussed in this paper.

中文翻译：

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LHC真空引燃器区段中的电子通量和压力动态与射束参数和射束管特性的关系

大强子对撞机（LHC）受电子云（EC）现象的影响，该现象可引起电子束不稳定，有害的热负荷以及真空系统中的压力增加。创新的专用系统称为真空先导扇区（VPS），借助电子拾取器和真空计，可以连续监控电子通量和压力信号。VPS系统安装在LHC存储环的室温，无磁场的部分中。几种技术面，例如易地同时测试了不可蒸发的吸气剂（NEG），无定形碳涂层和铜。这项研究的主要结果表明，EC信号具有：（1）在多步方式中对束数和束数的线性依赖性；（2）在给定束数下的多步阈值；（3）a （4）强烈依赖于填充模式和光束能量。不同表面之间的比较表明，无定形碳涂层由于其低的二次电子产率（SEY）和光电子产率（PY）而大大降低了EC的堆积，而铜和非原位NEG涂层的表面即使经过数月也经历了EC多次喷涂操作。该multipacting率系数是比铜更高的易地NEG，如SEY估算所预测。本文讨论了其他详细的实验观察结果。