Air exposure induced changes on coatings used to limit the e-cloud in accelerators

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Study of SEY degradation of amorphous carbon coatings

Publication . Bundaleski, Nenad; Candeias, S.; Santos, A.; Silva, Ana Cristina Gomes da; Teodoro, Orlando Manuel Neves Duarte; Silva, A. G.; DF – Departamento de Física; CeFITec – Centro de Física e Investigação Tecnológica

Deposition of low secondary electron yield (SEY) carbon coatings by magnetron sputtering onto the inner walls of the accelerator seems to be the most promising solution for suppressing the electron cloud problem. However, these coatings change their electron emission properties during long term exposure to air. The ageing process of carbon coated samples with initial SEY of about 0.9 received from CERN is studied as a function of exposure to different environments. It is shown that samples having the same initial SEY may age with different rates. The SEY increase can be correlated with the surface concentration of oxygen. Annealing of samples in air at 100-200 °C reduces the ageing rate and even recovers previously degraded samples. The result of annealing is reduction of the hydrogen content in the coatings by triggering its surface segregation followed by desorption

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Entidade financiadora

Fundação para a Ciência e a Tecnologia

Programa de financiamento

3599-PPCDT

Número da atribuição

CERN/FP/109313/2009