85 research outputs found
Cavity Phase Noise In Proton Storage Rings And Its Influence on Coupled synchrobetatron Oscillations
Beam Coupling Impedance Contribution of Flange Aperture Gaps: A Numerical Study for Elettra 2.0
The accurate analysis of any possible source of beam instability is mandatory for the design of a new particle accelerator, especially for high-current and ultra-low emittance synchrotrons. In the specific case of instabilities driven by the coupling between the charged particle beam and the electromagnetic field excited by the beam itself, the corresponding effect is estimated through the beam coupling impedance. The modeling of this effect is essential to perform a rigorous evaluation of the coupling impedance budget able to account for all devices present in the entire machine. To deal with this problem, this paper focuses on the estimation of the contribution of the joints lying between the different vacuum chamber sections, by performing a comparative numerical analysis that takes into account different aperture gaps between the flanges. The results point out the criticality of many small-impedance contributions that, added together, must be lower than a predefined impedance threshold
VUV and X-ray coherent light with tunable polarization from single-pass free-electron lasers
Tunable polarization over a wide spectral range is a required feature of
light sources employed to investigate the properties of local symmetry in both
condensed and low-density matter. Among new-generation sources, free-electron
lasers possess a unique combination of very attractive features, as they allow
to generate powerful and coherent ultra-short optical pulses in the VUV and
X-ray spectral range. However, the question remains open about the possibility
to freely vary the light polarization of a free-electron laser, when the latter
is operated in the so-called nonlinear harmonic-generation regime. In such
configuration, one collects the harmonics of the free-electron laser
fundamental emission, gaining access to the shortest possible wavelengths the
device can generate. In this letter we provide the first experimental
characterization of the polarization of the harmonic light produced by a
free-electron laser and we demonstrate a method to obtain tunable polarization
in the VUV and X-ray spectral range. Experimental results are successfully
compared to those obtained using a theoretical model based on the paraxial
solution of Maxwell's equations. Our findings can be expected to have a deep
impact on the design and realization of experiments requiring full control of
light polarization to explore the symmetry properties of matter samples
TOP-UP OPERATIONAL EXPERIENCE AT ELETTRA
Abstract Since May 2010 Elettra, operates in top-up at both 2 and 2.4 GeV user energies. In this paper the experience during more than a year of operation in top-up is discussed and the machine up time statistics are presented and compared with the before top up period
BEAM ORBIT STABILITY AT ELETTRA
Abstract The top-up operation established since 2010 at the Elettra third-generation synchrotron light source has solved the problems related to thermal drifts and beam current dependence, and a series of feedback loops acting on the machine optics and radio-frequency systems made easier to setup and operate the ring. Those systems together with the fast orbit feedback in operation since 2007, contributed to very high electron beam orbit stability. A description of the active systems and their performance, future perspectives as well as some still open issues will be presented and discussed
COMPARISON OF TRANSVERSE SINGLE BUNCH INSTABILITIES BETWEEN THE ESRF AND ELETTRA
Abstract Transverse single bunch instabilities are measured, analysed and compared between the ESRF and ELETTRA, to obtain a deeper insight, namely how different effects influence coherent transverse motions. Despite the basic similarity of the two machines, being both examples of third generation light sources, it is found that some distinct differences in the relevant parameters such as the energy and optics, as well as the impedance, lead to the appearance of instabilities in a notably different manner. As well as summarising the results of the experiments, modelling of the broadband impedance of the two machines and comparison with expectations are presented
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