The ASTeC Vacuum Science Group has been awarded Proof of Concept Funds (PoC) to investigate novel e-Cloud mitigation process. The award of £80k will support a recently drafted patent and investigation of potential commercialisation of this novel surface modification technique.
The ASTeC Vacuum Science Group at STFC Daresbury Laboratory in a collaboration with the School of Engineering at the University of Dundee, have recently engineered metal surfaces which have SEY < 1 as compared with traditional metal surfaces, typical - SEY ³ 1.9 . The technique involves rapid surface micro and nano structuring in argon and/or reactive atmosphere at room temperature using high power nanosecond pulsed laser systems at l = 1064 nm and l = 532 nm for processing of aluminium/stainless steel and copper foils, respectively. The average laser energy fluence will be at the ablation threshold of the substrates. The proposed technology looks certain to solve the long standing problem of electron multipacting in both the accelerator and space community.
The new engineered surface treatment does not introduce new material, it modifies the microstructure of the existing surface, therefore it is expected that the impact on wall impedance and wake fields should be less than from any other e-cloud mitigation techniques. Furthermore, this technique can easily be applied to existing vacuum surfaces where the improvement has to be done in-situ with minimum disturbance to the beam line. The treatment process is carried out in an inert gas environment at atmospheric pressure and therefore the actual cost of the process is considerably lower than other existing mitigation processes. The surface is highly reproducible and offers a very stable surface chemistry which can be influenced during the process. The surface is robust and is immune to any surface delamination which can be a detrimental problem for thin film coating. The treated surface remains the same material, therefore it is unlikely to cause any effect on the surface impedance but this needs to be verified.
Figure 1. The images of Cu samples: (a) untreated and (b) laser treated.
Figure 2. Early stage results for SEY of Cu as a function of incident electron energy for as-received and conditioned samples: Cu – untreated surface, Black Cu – treated surface.