• Accelerator Physics
• Beam Profile Monitors
• Free Electron Lasers
• Nanofabrication
• Wire Scanners

Over the past few years, the accelerator science community has striven more and more to generate electron beams with extremely low transverse size and emittance.
This research stems mainly from the requirements inherent in X-ray free electron lasers technology and novel accelerator development. The challenge of designing extremely low emittance accelerators brings the need for transverse beam size diagnostics with sub-micrometer resolution.
However, the resolution limit of state-of-the-art beam profile monitors prevents the possibility of measuring sub-micrometer spot sizes. The ultimate goal of this thesis is to develop a novel beam profile monitor capable of sub-micrometer resolution.
Our assessment study identifies wire scanners as the transverse profile monitors that best lend themselves to a resolution improvement.
In this context, the commissioning of a SwissFEL wire scanner is presented as first contribution of the thesis. The challenges tackled during the commissioning include but are not limited to: evaluating the reliability of the WSC beam prole measurements at different scanning velocities; studying the performances of both wire materials; selecting the best suited beam loss monitor to detect the electromagnetic shower generated in the interaction between the wire and the beam.
This preparatory work enabled acquiring the experience necessary to create the new device, and proved the limits of the existing wire scanners and of the conventional manufacturing technique.
As a result, we realised that a completely new design was necessary.
The second contribution of this thesis is the design, fabrication and experimental test
of a novel WSC on-a-chip with sub-micrometer resolution. SwissFEL WSCs feature a maximum spatial resolution of 1.25 μm, which is mainly determined by the wire diameter. The resolution of a wire scanner is indeed limited by the encoder readout, the wire diameter and vibrations. The wire diameter defines the so-called geometrical resolution. In SwissFEL, a geometrical resolution of 1.25 μm was reached with a 5 μm tungsten wire. The wire scanner motion system is provided of an encoder with resolution of 0.1 μm. The measured wire-vibrations are largely below the geometrical resolution. Therefore, the wire diameter is the bottleneck in the spatial resolution. A natural way to increase the resolution is to decrease this value. However, the strength of a wire reduces with its diameter. Therefore, the conventional manufacturing technique of stretching a wire onto a wire fork limits its width to a few micrometers. To overcome this limitation, this thesis proposes an innovative design featuring micrometer sized metallic stripes written on a chip. A novel nanofabrication technique has been exploited to produce a 1 μm wide gold stripe on a membrane by
electron-beam lithography and electroplating. The proposed design ensures a (rms)geometrical resolution of 0.3 μm and enables the integration of a wire scanner on a chip.
The opportunity of measuring sub-micrometer electron beams is vital to test experimentally the WSC on-a-chip, and assess its performances in terms of resolution. Hence, the thesis describes the generation of a sub-micrometer electron beam at particle energy of 330 MeV, and bunch charge below 1 pC. We attained a measured vertical emittance of 53 nm with estimated errors of  10%, and an expected vertical beam size of 460 nm. The generated beam has been characterized through the
fabricated prototype.