Marcel Himmerlich
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View article: Decommissioning and post-irradiation examination of the LHC beam dumps
Decommissioning and post-irradiation examination of the LHC beam dumps Open
The LHC beam dumps are responsible for the safe absorption of the Large Hadron Collider (LHC) particle beams. In 2018, the two 6.4-tonne beam dumps that had been in operation since the LHC’s startup in 2008 were removed and replaced with u…
View article: Characterising the Surface Resistance of Laser-Treated LHC Beam Screens with the Shielded Pair Method
Characterising the Surface Resistance of Laser-Treated LHC Beam Screens with the Shielded Pair Method Open
The presence of strong electron clouds in the quadrupole magnetic field regions of the Large Hadron Collider (LHC) leads to considerable heating that poses challenges for the cryogenic cooling system, and under certain conditions to proton…
View article: Ferrites with a Minimized Secondary Electron Yield
Ferrites with a Minimized Secondary Electron Yield Open
Ferrites are an essential material in modern industry due to their exceptional magnetic properties and high resistivity. Many applications of ferrites necessitate exposure to high energy electrons, particularly space science and particle a…
View article: Selective laser processing of particle accelerator beam screen surfaces for electron cloud mitigation
Selective laser processing of particle accelerator beam screen surfaces for electron cloud mitigation Open
The material properties of laser-treated LHC beam screens with low SEY are examined to validate compatibility with the operation conditions of particle accelerators.
View article: Influence of nanoparticulates and microgrooves on the secondary electron yield and electrical resistance of laser-treated copper surfaces
Influence of nanoparticulates and microgrooves on the secondary electron yield and electrical resistance of laser-treated copper surfaces Open
Laser surface structuring has proven to be an effective technique for achieving a copper surface with secondary electron yield (SEY) values close to or below unity. However, the attributes that minimize SEY, such as moderately deep grooves…
View article: Cleaning of laser-induced periodic surface structures on copper by gentle wet chemical processing
Cleaning of laser-induced periodic surface structures on copper by gentle wet chemical processing Open
•Cleaning of 365 nm LIPSS from debris of with microemulsions has been demonstrated.•Excellent debris and particles removal while maintaining the LIPSS pattern were found.•The cleaning mechanism is dominated of selective dissolution of nano…
View article: LHC Upgrades in preparation of Run 3
LHC Upgrades in preparation of Run 3 Open
The Large Hadron Collider (LHC) Long Shutdown 2 (2019–2021), following LHC Run 2, was primarily dedicated to the upgrade of the LHC Injectors but it included also a significant amount of activities aimed at consolidation of the LHC machine …
View article: Performance of laser patterned copper plasmonic photocathodes
Performance of laser patterned copper plasmonic photocathodes Open
We study ultrafast laser surface nanopatterning as an alternative to improve the photo-emissive properties of metallic photocathodes. By tailoring the physical dimensions of these surface nanostructures, one can localize the optical field …
View article: Plasma Cleaning of Hydrocarbon and Carbon Contaminated Surfaces of Accelerator Components
Plasma Cleaning of Hydrocarbon and Carbon Contaminated Surfaces of Accelerator Components Open
To achieve the vacuum quality required for the operation of particle accelerators, the surface of the vacuum vessels must be clean from hydrocarbons. This is usually achieved by wet chemistry processes, e.g., degreasing chemical baths that…
View article: RF Characterisation of Laser Treated Copper Surfaces for the Mitigation of Electron Cloud in Accelerators
RF Characterisation of Laser Treated Copper Surfaces for the Mitigation of Electron Cloud in Accelerators Open
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…
View article: Pulse Duration Dependence of Infrared Laser-Induced Secondary Electron Yield Reduction of Copper Surfaces
Pulse Duration Dependence of Infrared Laser-Induced Secondary Electron Yield Reduction of Copper Surfaces Open
The irradiation of metals with ultrashort laser pulses enables the rapid and cost-effective production of nanostructured surfaces with a wide range of industrial applications. The laser-induced surface roughening modifies the interaction p…
View article: Hot electron enhanced photoemission from laser fabricated plasmonic photocathodes
Hot electron enhanced photoemission from laser fabricated plasmonic photocathodes Open
Photocathodes are key elements in high-brightness electron sources and ubiquitous in the operation of large-scale accelerators, although their operation is often limited by their quantum efficiency and lifetime. Here, we propose to overcom…
View article: Picosecond pulsed 532 nm laser system for roughening and secondary electron yield reduction of inner surfaces of up to 15 m long tubes
Picosecond pulsed 532 nm laser system for roughening and secondary electron yield reduction of inner surfaces of up to 15 m long tubes Open
Laser-induced surface structuring is a promising method to suppress electron mulitpacting in the vacuum pipes of particle accelerators. Electrons are scattered inside the rough surface structure, resulting in a low Secondary Electron Yield…
View article: The Role of Hydrogen Incorporation into Amorphous Carbon Films in the Change of the Secondary Electron Yield
The Role of Hydrogen Incorporation into Amorphous Carbon Films in the Change of the Secondary Electron Yield Open
Over the last few years, there has been increasing interest in the use of amorphous carbon thin films with low secondary electron yield (SEY) to mitigate electron multipacting in particle accelerators and RF devices. Previous works found t…
View article: The Role of Hydrogen Incorporation into Amorphous Carbon Films in the Change of the Secondary Electron Yield
The Role of Hydrogen Incorporation into Amorphous Carbon Films in the Change of the Secondary Electron Yield Open
The interest on amorphous carbon thin films with low secondary electron yield (SEY) has been increasing in the last years, to mitigate electron multipacting in particle accelerators and in RF devices. Previous works found that the SEY incr…
View article: Amorphous carbon thin films: Mechanisms of hydrogen incorporation during magnetron sputtering and consequences for the secondary electron emission
Amorphous carbon thin films: Mechanisms of hydrogen incorporation during magnetron sputtering and consequences for the secondary electron emission Open
Amorphous carbon (a-C) films, having low secondary electron yield (SEY), are used at CERN to suppress electron multipacting in the beam pipes of particle accelerators. It was already demonstrated that hydrogen impurities increase the SEY o…
View article: Out of focus ultrafast processing of metals for reduced secondary electron yield
Out of focus ultrafast processing of metals for reduced secondary electron yield Open
We have demonstrated out-of-focus ultrafast pulsed laser processing of copper with a variable working distance, without the need for mechanical movement. This was achieved by employing a diffractive optical element. The method has been dem…
View article: Influence of wavelength and accumulated fluence at picosecond laser-induced surface roughening of copper on secondary electron yield
Influence of wavelength and accumulated fluence at picosecond laser-induced surface roughening of copper on secondary electron yield Open
Ultrashort-pulse laser processing of copper is performed in air to reduce the secondary electron yield (SEY). By UV (355 nm), green (532 nm), and IR (1064 nm) laser-light induced surface modification, this study investigates the influence …
View article: Origin and mitigation of the beam-induced surface modifications of the LHC beam screens
Origin and mitigation of the beam-induced surface modifications of the LHC beam screens Open
All over Run 2, the LHC beam-induced heat load on the cryogenic system exhibited a wide scattering along the ring. Studies ascribed the heat source to electron cloud build-up, indicating an unexpected high Secondary Electron Yield (SEY) of…
View article: Efficient Combination of Surface Texturing and Functional Coating for Very Low Secondary Electron Yield Surfaces and Rough Nonevaporable Getter Films
Efficient Combination of Surface Texturing and Functional Coating for Very Low Secondary Electron Yield Surfaces and Rough Nonevaporable Getter Films Open
The formation of a fissured copper surface by picosecond pulsed laser irradiation is combined with functional coatings consisting of Ti and amorphous carbon layers or a Ti–Zr–V compound film to fabricate surfaces with the maximum of the se…
View article: Secondary electron yield reduction of copper after 355 nm ultrashort pulse laser ablation
Secondary electron yield reduction of copper after 355 nm ultrashort pulse laser ablation Open
Nanostructured surfaces exhibit remarkable chemical, physical and microbiological properties and have therefore various technical and industrial applications. The ultrashort laser pulse irradiation (wavelength λ = 355 nm, pulse duration Δt…
View article: Secondary electron yield engineering of copper surfaces by 532 nm ultrashort laser pulses
Secondary electron yield engineering of copper surfaces by 532 nm ultrashort laser pulses Open
Nanostructured surfaces exhibit outstanding properties and enable manifold industrial applications. In this study the laser surface processing of polycrystalline, flat copper surfaces by 532 nm picosecond laser irradiation for secondary el…
View article: Stability and lifetime study of carbon nanotubes as cold electron field emitters for electron cooling in the CERN extra low energy antiproton ring
Stability and lifetime study of carbon nanotubes as cold electron field emitters for electron cooling in the CERN extra low energy antiproton ring Open
Electron cooling is a fundamental process to guarantee the beam quality in low energy antimatter facilities. In extra low energy antiproton, the electron cooler reduces the emittance blowup of the antiproton beam and thus delivers a focuse…
View article: Beam-induced surface modifications as a critical source of heat loads in the Large Hadron Collider
Beam-induced surface modifications as a critical source of heat loads in the Large Hadron Collider Open
Beam-induced heat loads on the cryogenic regions of the Large Hadron Collider (LHC) exhibit a wide and unexpected dispersion along the accelerator, with potential impact on the performance of its High-Luminosity upgrade. Studies related th…
View article: Secondary electron yield reduction by femtosecond pulse laser-induced periodic surface structuring
Secondary electron yield reduction by femtosecond pulse laser-induced periodic surface structuring Open
The electron-cloud phenomenon is one cause of beam instabilities in high intensity positive particle accelerators. Among the proposed techniques to mitigate or control this detrimental effect, micro-/nano-geometrical modifications of vacuu…