8 research outputs found
RF Characterisation of Laser Treated Copper Surfaces for the Mitigation of Electron Cloud in Accelerators
In accelerator beam chambers and RF waveguides, electron cloud and multipacting can be mitigated effectively by reducing the secondary electron yield (SEY). In recent years, it has been established that laser-engineered surface structuring is a very efficient method to create a copper surface with a SEY maximum close to or even below unity. Different laser pulse durations, from nanoseconds to picoseconds, can be used to change surface morphology. Conversely, the characteristics that minimise the SEY, such as the moderately deep grooves and the redeposited nanoparticles, might have unfavourable consequences, including increased RF surface resistance. In this study, we describe the techniques used to measure the surface resistance of laser-treated copper samples using an enhanced dielectric resonator with 12 cm diameter sample sizes operating in the GHz range. The quantification basis lies in a non-contact measurement of the high-frequency losses, focusing on understanding the variation of surface resistance levels depending on the specifics of the treatment and possible post-treatment cleaning procedures.</p
RF Characterisation of Laser Treated Copper Surfaces for the Mitigation of Electron Cloud in Accelerators
In accelerator beam chambers and RF waveguides, electron cloud and multipacting can be mitigated effectively by reducing the secondary electron yield (SEY). In recent years, it has been established that laser-engineered surface structuring is a very efficient method to create a copper surface with a SEY maximum close to or even below unity. Different laser pulse durations, from nanoseconds to picoseconds, can be used to change surface morphology. Conversely, the characteristics that minimise the SEY, such as the moderately deep grooves and the redeposited nanoparticles, might have unfavourable consequences, including increased RF surface resistance. In this study, we describe the techniques used to measure the surface resistance of laser-treated copper samples using an enhanced dielectric resonator with 12 cm diameter sample sizes operating in the GHz range. The quantification basis lies in a non-contact measurement of the high-frequency losses, focusing on understanding the variation of surface resistance levels depending on the specifics of the treatment and possible post-treatment cleaning procedures.</p
Characterisation of copper and stainless steel surfaces treated with laser ablation surface engineering
REBa2Cu3O7 coated conductors as a beam screen coating: Using the classical rigid-fluxon model to link surface resistance to microstructure
Coated conductor technology for the beamscreen chamber of future high energy circular colliders
The surface resistance of state-of-the-art REBa2Cu3O7−x coated conductors has been measured
at 8 GHz versus temperature and magnetic field. We show that the surface resistance of
REBa2Cu3O7−x strongly depends on the microstructure of the material. We have compared our
results to those determined by the rigid fluxon model. The model gives a very good qualitative
description of our data, opening the door to unravel the effect of material microstructure and
vortex interactions on the surface resistance of high temperature superconductors. Moreover, it
provides a powerful tool to design the best coated conductor architecture that minimizes the infield
surface resistance. We have found that the surface resistance of REBa2Cu3O7−x at 50 K and
up to 9 T is lower than that of copper. This fact poses coated conductors as strong candidate to
substitute copper as a beamscreen coating in CERN’s future circular collider. To this end we
have also analyzed the secondary electron yield (SEY) of REBa2Cu3O7−x and found a
compatible coating made of sputtered Ti and amorphous carbon that decreases the SEY close to
unity, a mandatory requirement for the beamscreen chamber of a circular collider in order to
prevent the electron-cloud phenomenon.Peer reviewe