The effect of air exposure on SEY and surface composition of laser treated copper applied in accelerators

TL;DR

This study investigates how air exposure and cleaning affect the surface chemistry and secondary electron yield of laser-treated copper used in accelerators, revealing significant changes over time.

Contribution

It provides new insights into the long-term effects of air exposure on laser-treated copper surfaces, including SEY increase and surface chemistry alterations.

Findings

SEY increases by 11-20% after 10-21 months of air exposure

Surface oxygen and carbon content significantly increase over time

Copper surface composition decreases substantially after cleaning and air exposure

Abstract

In this paper, the effect of air exposure and acetone cleaning on the secondary electron yield (SEY) of laser treated copper were investigated and discussed. The SEY of laser treated copper samples after acetone cleaning and air exposure were measured. After 10 to 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 XPS. The XPS results show that the concentration of Cu decreased by about 61%~70% after acetone cleaning and decreased by a further 36%~70% after 10 to 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 to 21 months air exposure. The increase of SEY is explained in terms of the introduction of impurities, such as oxide, carbide etc.