Abstract
The detailed study of the low energy Secondary Electron Yield (LE-SEY) of technical Cu for very low electron landing energies (from 0 to 30 eV) is very important for electron cloud build up in high intensity accelerators and in many other fields of research. However, LE-SEY has been rarely addressed due to the intrinsic experimental complexity to control very low energy electrons. Furthermore, several results published in the past have been recently questioned for allegedly suering from experimental systematics. Here, we critically review the experimental method used to study LE - SEY and define more precise energy regions, in which the experimental data can be considered valid. E-cloud simulations are than performed to address the impact of such results on electron cloud predictions in the LHC.
Highlights
An extremely vast range of research spanning from detectors, photon or electron-multipliers, high power microwave tubes, systems for satellite applications [1], radio-frequency cavities [2], to optics for extreme ultraviolet (EUV) lithography [3], bases some of their essential functionalities on the number of electrons produced by a surface when hit by other electrons
It is clear that the best performance of present and future accelerators can be achieved if Electron Cloud Effects (ECE) are understood, predicted and mitigated
For the case of the Cu sample representative of Large Hadron Collider (LHC), we found a secondary electron yield (SEY) always higher the ∼0.5 for the entire LE range, and this is of stimulus to address the effects of such low energy secondary electron yield (LE-SEY) behavior on e− cloud simulations for the LHC, as it will be done in the final section
Summary
An extremely vast range of research spanning from detectors, photon or electron-multipliers, high power microwave tubes, systems for satellite applications [1], radio-frequency cavities [2], to optics for extreme ultraviolet (EUV) lithography [3], bases some of their essential functionalities on the number of electrons produced by a surface when hit by other electrons. When the effective SEY at the chamber walls is larger than unity, the electron population grows rapidly in time with successive bunch passages This can lead to a high electron density, and, to detrimental effects such as a rapid pressure rise in the vacuum chamber resulting in beam loss. This phenomenon is called electron cloud (EC) build-up, and has been identified as source of limitations of accelerator performances in the SPS, Large Hadron Collider (LHC), the positron rings at the B (Beauty) factories PEP-II, KEKB, etc. At LHC SEY reduction is expected to occur during initial operations (scrubbing or conditioning) and is considered necessary to reach nominal operation [7,8,9,10]
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