Speaker
Description
Laser-induced surface roughening facilitates secondary electron yield reduction of materials [1]. The lab-based demonstration on small scale in 2014 motivated an initiative to scale-up the technology for processing of long vacuum components with inner surfaces to be treated in apertures < 50 mm, which is challenging. To address this, we have developed a technique that enables the selective transformation of the inner beam screen (BS) surfaces in LHC standalone magnets for electron cloud mitigation [2]. This requires scanning the light generated by a pulsed laser across the surface of ~10 m long BSs. The developed system consists of an IR laser and a 17 m long optical fiber that transmits the light to an inchworm mole, which houses an optical focusing unit and allows to scan the laser spot. We will present our solutions to the emerged challenges: i) mitigate surface oxidation, ii) avoid the contamination of cryosorbers, iii) integrate a synchronized fiber management system, iv) assure an acceptable treatment speed, v) find a compromise to match all material requirements, vi) extract ablated particulates, vii) monitor the process for quality control, and viii) perform a post-processing cleaning. By combining these steps, the influence on the beam impedance was minimized, and the compatibility with LHC operation was demonstrated.
[1] R. Valizadeh et al, Appl. Phys. Lett. 105 (2014), 231605.
[2] Elena Bez et al., RSC Appl. Interfaces 2 (2025), 521.
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