Accelerator Seminar

[Accelerator Seminar I] Reduction of Secondary Electron Yield for E-cloud Mitigation by Laser Ablation Surface Engineering

Start:2017/10/27 (Fri) 10:00 AM
End:2017/10/27 (Fri) 11:00 AM
Location:Meeting room, Fifth floor, 3-goukan (3rd building), Tsukuba campus

Speaker:Dr. R. Valizadeh Senior Scientist ASTeC (Accelerator Science and Technology Centre STFC Daresbury)
Contact:Yusuke Suetsugu (PHS: 4294)


Photon and Secondary Electron Yield (PEY and SEY) for the surface of vacuum chamber play a key role in the beam induced electron multipacting (BIEM) and the electron cloud in positively charged particle accelerators, waveguides and detectors, and may limit the performance of these devices.
Developing surfaces with low Secondary Electron Yield (SEY) is one of main ways of mitigating e-cloud and BIEM in high-energy charged particle accelerators.
Recently, a low SEY< 0.85 for as-received metal surfaces modified by a nanosecond pulsed laser was reported for the first time.
This invention by R. Valizadeh and O. Malyshev at ASTeC has been further investigated as a function of various treatments, specifically as a function of different laser irradiation parameters.
We explore and study the influence of micro- and nano-structures induced by laser surface treatment in air of copper samples as a function of various laser irradiation parameters such as peak power, laser wavelength (l = 355 nm and 1064 nm), number of pulses per point (scan speed and repetition rate) and fluence, on the SEY.
The surface chemical composition was determined by x-ray photoelectron spectroscopy (XPS) which revealed that heating resulted in diffusion of oxygen into the bulk and induced the transformation of CuO to sub-stoichiometric oxide.
The surface topography was examined with high resolution scanning electron microscopy (HRSEM) which showed that the laser-treated surfaces are dominated by microstructure groves and nanostructure features.
The surface resistance of these coating a key parameter for the beam impedance, the comparison of untreated and laser treated surfaces will be reported.

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