Comparison of Carbon Thin Films with Low Secondary Electron Yield Deposited in Neon and Argon

Yuxin Zhang,Xiaoqin Ge,Wei Wei,Jieqiong Shao,Bangle Zhu,Yong Wang,Yigang Wang,Sihui Wang

doi:10.3390/coatings10090884

Abstract

Modification of vacuum chamber surface properties by introducing a layer of material with low secondary electron yield (SEY) is one of the most useful solutions to suppress the electron-cloud in high-energy particle accelerators. In the present work, amorphous carbon thin films have been produced by DC magnetron sputtering with Neon and Argon sputtering gases. Microstructures of the thin films have been characterized by using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The sp2 and sp3 hybridized carbon atoms are evaluated using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The amorphous carbon coatings comprise tiny granularities of tens of nanometers. The amorphous carbon films show more graphite-like properties as revealed by XPS and Raman spectroscopy. The secondary electron emission measurement results indicate that amorphous carbon coatings present SEY of <1.2. The thin film deposited by Ne exhibits a higher sp2 hybridization content, leading to a slightly lower SEY compared with the film produced with Ar.

Highlights

The vacuum chamber of high-energy particle accelerators contains small amounts of residual gas, ions, low-energy electrons
Amorphous carbon thin films were produced by a DC magnetron sputtering system and secondary electron yield (SEY)
The experiment results showed that amorphous carbon thin film has low inherent SEY, compared with bare stainless-steel substrate

Summary

Introduction

The vacuum chamber of high-energy particle accelerators contains small amounts of residual gas, ions, low-energy electrons. Synchrotron radiation from the particle beam generates electrons by photoemission from the wall of the beam pipe or through ionisation of the residual gas by beam-gas interactions. A large density of electrons can build up inside the beam chamber, leading to the formation of an electron cloud. Electron cloud build-up can significantly affect the quality of the beam and machine operation such as LHC, KEKB, RHIC, PEP=II and so forth [2]. The electrons can desorb gas from the walls increasing the pressure in the beam pipe or RF cavities [6]. Electron cloud is a main limitation for the achievement of high-quality beam in high-energy modern accelerators

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Discussion

Conclusion