Detailed investigation of the low energy secondary electron yield of technical Cu and its relevance for the LHC

Abstract

The detailed study of the low energy secondary electron yield (LE-SEY) of technical Cu for low electron energies (from 0 to 20 eV) is very important for electron cloud build up in high intensity accelerators and in many other fields of research. Different devices base their functionalities on the number of electrons produced by a surface when hit by other electrons, namely its SEY, and, in most cases, on its very low energy behavior. 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, allegedly suffering from experimental systematics. Here, we critically review the experimental method used to study LE-SEY and precisely define the energy region in which the experimental data can be considered valid. By analyzing the significantly different behavior of LE-SEY in clean polycrystalline Cu (going toward zero at zero impinging energies) and in its as received technical counterpart (maintaining a significant value in the entire region), we solve most, if not all, of the apparent controversy present in the literature, producing important inputs for better understanding the device performances related to their LE-SEY. Simulations are then performed to address the impact of such results on electron cloud predictions in the LH

Ionizing Doses Calculations for Low Energy Electrons in Silicon and Aluminum

“…In the complex dielectric function theory, the total inelastic mean free path λ can be calculated using equation (1) where a 0 =5.29x10 -11 m is the Bohr radius, T the kinetic energy of the incident electron, and (ℏ , ℏ ) the exact dielectric function of the solid with ℏ and ℏ the energy and momentum transferred to the electrons of the solid [22].…”

“…he study of low energy electron transport in matter is of great interest for many fields of applications. For instance, the amount of electrons emitted by a surface when hit by an incident electron, or Electron Emission Yield (EEY), is of particular importance for particle accelerators and satellite communication devices performances [1]- [2]. In the latter, electrons of a few tens of eV are known to cause vacuum discharges (Multipactor effect) that can degrade the devices or, at least, limit the transmitted power.…”

Novel measurement technique for the electromagnetic characterization of coating materials in the sub-THz frequency range

“…These primary electrons may hit the inner wall of the beam pipe, causing secondary emission or being elastically reflected [1]. If the secondary electron yield (SEY) of the surface material is greater than unity, the number of electrons grows exponentially leading to beam instabilities and many other side effects [2,3]. In order to reduce the SEY value in the pipe walls, a-C coatings have been extensively tested [4] and used [5] at the CERN SPS accelerator and other experiments [6] with very effective results.…”

Mitigating the electron cloud effect in the SuperKEKB positron ring

“…Note, however, that while δ max is the most important parameter, it is not the only one that determines n e . For example, the electron reflectivity at very small energies is also a sensitive parameter [71].…”