The Effect of Air Exposure on SEY and Surface Composition of Laser Treated Copper Applied in Accelerators

In this paper, the effect of air exposure and acetone cleaning on the secondary electron yield (SEY) of laser treated copper applied in accelerators for the inhibition of electron cloud was investigated and discussed. The SEY of laser treated copper samples after acetone cleaning and air exposure was measured. After 10–21 months air exposure, the maximum SEY increased by about 11%–20%. Furthermore, changes of carbon, copper, and oxygen chemistry states from sample surface after acetone and air exposure were studied by means of X-ray photoelectron spectroscopy. The XPS results show that the concentration of Cu from the surface of the samples with the thickness of 500 and <inline-formula> <tex-math notation="LaTeX">$20~\mu \text{m}$ </tex-math></inline-formula> decreased by about 61%–70% after acetone cleaning and decreased by a further 36%–70% after 10–21 months air exposure. Moreover, the XPS measurement reflects the significant increase of the total percentages of C and O after acetone cleaning, and further increase after 10–21 months air exposure. The increase of SEY is explained in terms of the introduction of impurities, such as oxide and carbide.

[1]  B. Henrist,et al.  Electron Cloud Heat Load Estimations for the LHC Using Strip and Retarding Field Detectors , 2003 .

[2]  W. Allan Gillespie,et al.  APS : First accelerator test of vacuum components with laser-engineered surfaces for electron-cloud mitigation , 2017 .

[3]  W. Fischer,et al.  Electron cloud observations and cures in the Relativistic Heavy Ion Collider , 2008 .

[4]  O. Grobner,et al.  Electron cloud and beam scrubbing in the LHC , 1999, Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366).

[5]  Pinto,et al.  AMORPHUS CARBON COATINGS FOR MITIGATION OF ELECTRON CLOUD IN THE CERN SPS , 2010 .

[6]  D. Davino,et al.  Electron-cloud mitigation in the Spallation Neutron Source ring , 2003, Proceedings of the 2003 Particle Accelerator Conference.

[7]  T. Ishibashi,et al.  Achievements and problems in the first commissioning of superKEKB vacuum system , 2017 .

[8]  O. Malyshev,et al.  Low secondary electron yield of laser treated surfaces of copper, aluminium and stainless steel , 2016 .

[9]  K. Kim.  Charge transfer transition accompanying x-ray photoionization in transition-metal compounds , 1974 .

[10]  A. Rosencwaig,et al.  X-ray photoemission satellites; surface or bulk effect? , 1972 .

[11]  K. Harkay,et al.  Theory and measurement of the electron cloud effect , 1999, Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366).

[12]  R. Cimino,et al.  Electron cloud in accelerators , 2014 .

[13]  Jie Wang,et al.  Secondary electron emission characteristics of graphene films with copper substrate , 2016 .

[14]  M. Taborelli,et al.  Carbon coatings with low secondary electron yield , 2013 .

[15]  M. Morrone,et al.  Material characterisation and preliminary mechanical design for the HL-LHC shielded beam screens operating at cryogenic temperatures. , 2015 .

[16]  Frank Zimmermann,et al.  Electron cloud effects on beam evolution in a circular accelerator , 2003 .

[17]  W. Allan Gillespie,et al.  Low secondary electron yield engineered surface for electron cloud mitigation , 2014 .