Felix Zimmermann

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We report on the welding of fused silica with bursts of ultrashort laser pulses. By optimizing the burst frequency and repetition rate, we were able to achieve a breaking resistance of up to 96% of the bulk material, which is significantly higher than conventional high repetition rate laser bonding. The main reason for this stability increase is the reduced(More)
We report on nanostructures induced by femtosecond laser pulses in the bulk of Germanium-doped silica glasses. For studying structural properties of the nanostructure constituents small-angle x-ray scattering and SEM served to map pore size, filling factor and periodicity. Our results show that with increasing the Ge doping concentration, the aspect ratio(More)
Computer simulations for the CERN muon storage ring confirm the absence of beam-induced multipacting. Thus electron-cloud build up along the bunch train is not expected to be a problem. Geneva, Switzerland December 18, 2000 We first describe a few basic considerations on electron-cloud build up, scaling from the LHC, and then report simulation results.(More)
The European Accelerator Network on High Energy High Intensity Hadron Beams (CARE HHH) is developing scenarios for luminosity and energy upgrades of the Large Hadron Collider (LHC). The LHC upgrade options under consideration differ in terms of beam parameters, electroncloud effects, beam-beam compensation, use of crab cavities, and interaction-region(More)
A detailed study of the influence of the pulse duration, from the femtosecond to the nanosecond regime, on the evolution of the hole shape and depth during percussion drilling in silicon is presented. Real-time backlight imaging of the hole development is obtained for holes up to 2 mm deep with aspect ratios extending to 25:1. For low pulse energies, the(More)
The absorption and heat accumulation of successive ultrashort laser pulses in fused silica leads to melting of the material. We analyze the structure and formation of disruptions that occur within the trace of the molten material. We employed focused ion beam (FIB) milling to reveal the inner structure of these disruptions. The disruptions consist of(More)
In this study, we report on the erasure and rewriting of nanogratings by femtosecond laser pulses in the bulk of fused silica. To map the structural processes during rewriting, a combination of optical retardance measurement, small angle X-ray scattering, and scanning electron microscopy was used. The results reveal that already few pulses lead to erasure(More)
The OECD is a unique forum where the governments of 30 democracies work together to address the economic, social and environmental challenges of globalisation. The OECD is also at the forefront of efforts to understand and to help governments respond to new developments and concerns, such as corporate governance, the information economy and the challenges(More)