A compact and cost-effective hard X-ray free-electron laser driven by a high-brightness and low-energy electron beam

We present the first lasing results of SwissFEL, a hard X-ray free-electron laser (FEL) that recently came into operation at the Paul Scherrer Institute in Switzerland. SwissFEL is a very stable, compact and cost-effective X-ray FEL facility driven by a low-energy and ultra-low-emittance electron beam travelling through short-period undulators. It delivers stable hard X-ray FEL radiation at 1-Å wavelength with pulse energies of more than 500 μJ, pulse durations of ~30 fs (root mean square) and spectral bandwidth below the per-mil level. Using special configurations, we have produced pulses shorter than 1 fs and, in a different set-up, broadband radiation with an unprecedented bandwidth of ~2%. The extremely small emittance demonstrated at SwissFEL paves the way for even more compact and affordable hard X-ray FELs, potentially boosting the number of facilities worldwide and thereby expanding the population of the scientific community that has access to X-ray FEL radiation

Phase-space manipulations of electron beams for x-ray free-electron lasers and inverse Compton scattering sources

Committee members: Erdelyi, Bela; Yamplosky, Nikolai; Zutshi, Vishnu.Advisor: Piot, Philippe.Includes illustrations.Includes bibliographical references.This dissertation describes advanced techniques of phase space manipulations of the electron beam for improving performance and efficiency of high brightness X-ray light sources based on the free-electron Laser (FEL) and inverse-Compton scattering (ICS) processes. In particular, it first discusses a novel bunch-compression scheme based on a double transverse-to-longitudinal phase-space exchanger - dubbed emittance exchanger (EEX) - separated by a demagnifying transverse-optics system. While the outline of the scheme is quite sophisticated, the basic physics behind it is quite straight-forward. The benefits and disadvantages of these scheme are compared to the conventional approach of compressing a bunch using a magnetic bunch-compression chicane. The second scheme discussed in this dissertation is a novel beamline for imposing and removing the energy slew along the bunch also known as chirping and dechirping the beam in the accelerator community. This scheme consists of transverse deflecting cavities separated by drifts and relies on imposing and removing the transverse-longitudinal correlations on the electron beam. The benefits of this alternative method are compared with standard schemes of chirping and dechirping the beam via an off-crest acceleration. Finally, a novel 6-dimensional theory of the ICS source concludes this dissertation. It derives the photon distribution in 6D phase space describing radiation produced in the process of scattering a laser pulse off a relativistic electron beam as a function of electron distribution in the phase space using the Wigner function formalism. This result opens up the possibility for the optimization of the brightness of an ICS source via imposing transverse-longitudinal correlations on the beam.Ph.D. (Doctor of Philosophy

Dual-scattering foil installation at CLEAR

The CLEAR user facility at CERN allows users to receive a beam with energy up to 200 MeV, allowing flexibility in intensity, beam size and bunch structures. Separate from the main CERN accelerator complex, it is capable of hosting numerous experiments and catering to a broad array of needs with rapid installations at 2 test stands on the beamline.The CLEAR beam is characteristically Gaussian when optimised for transport and a small transverse beam size. It would be highly desirable for many applications but particularly those of a medical nature, to be able to provide a ‘flat’ beam with a uniform intensity distribution over a significant component of its transverse component.Over the CLEAR winter shutdown, the operators installed a dual-scattering system in the CLEAR beamline to provide this. It was placed several metres upstream of the beamline end to reduce X-ray contamination in the flattened beam and increase total transmission of the beam. Studies on the flattened beam composition in terms of structure and dose were carried out, also utilising a dipole directly upstream of the in-air test stand to separate the electron and X-ray beams for analysis

Dual-scattering foil installation at CLEAR

The CLEAR user facility at CERN allows users to receive a beam with energy up to 200 MeV, allowing flexibility in intensity, beam size and bunch structures. Separate from the main CERN accelerator complex, it is capable of hosting numerous experiments and catering to a broad array of needs with rapid installations at 2 test stands on the beamline.The CLEAR beam is characteristically Gaussian when optimised for transport and a small transverse beam size. It would be highly desirable for many applications but particularly those of a medical nature, to be able to provide a ‘flat’ beam with a uniform intensity distribution over a significant component of its transverse component.Over the CLEAR winter shutdown, the operators installed a dual-scattering system in the CLEAR beamline to provide this. It was placed several metres upstream of the beamline end to reduce X-ray contamination in the flattened beam and increase total transmission of the beam. Studies on the flattened beam composition in terms of structure and dose were carried out, also utilising a dipole directly upstream of the in-air test stand to separate the electron and X-ray beams for analysis