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Using proper beam energy chirp and the undulator detuning effect, we propose
a modified optical replica synthesizer scheme to characterize the temporal
structure of a relativistic electron bunch, which predicts a 100-fs temporal
resolution in numerical simulation. The proof of principle experiment
demonstrates a peak current of 9 A and a slice ener...
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... at the 2 nd harmonic of the seed wavelength. It is found that, for obtaining a significant coherent radiation in the replica synthesizer radiator, the effective modulator current is from 46 to 48A and from 43 to 54A without and with energy chirp respectively, which is a simple criterion to check the validation of the proposed ORS operation. Fig. 4 presents the measured current profile, where the absolute value of current distribution is normalized from pulse charge of 100pC. Fig. 4 indicates a peak current of 9A and a FWHM bunch length of 12ps. As shown in Fig. 5, we also have measured the slice energy spread and slice energy modulation. The typical slice energy spread of the ...
Context 2
... radiator, the effective modulator current is from 46 to 48A and from 43 to 54A without and with energy chirp respectively, which is a simple criterion to check the validation of the proposed ORS operation. Fig. 4 presents the measured current profile, where the absolute value of current distribution is normalized from pulse charge of 100pC. Fig. 4 indicates a peak current of 9A and a FWHM bunch length of 12ps. As shown in Fig. 5, we also have measured the slice energy spread and slice energy modulation. The typical slice energy spread of the electron bunch is 0.5keV, which agrees well with start-to-end dynamics. The maximum energy modulation induced by 1047nm laser pulse is ...
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Citations
Polarization switching of light sources is required over a wide spectral range to investigate the symmetry of
matter. In this paper,we report the first experimentaldemonstration of the crossed-planar undulators technique
at a seeded free-electron laser, which holds great promise for the full control and fast switching of the
polarization of short-wavelength radiation. In the experiment, the polarization state of the coherent radiation at
the secondharmonic of the seed laser is switched successfully.Theexperimental results confirm the theory and
pave the way for applying the crossed-planar undulators technique for seeded x-ray free-electron lasers.
Independently from conventional electron beam based procedures, the photon beam based diagnostic is
an alternative way for electron trajectory alignment and commissioning of numerous undulator cells in
high-gain short-wavelength free-electron lasers (FELs). In this paper, using the microbunched electron
beam and the undulator fine-tuning technique, a novel method based on the spatial profile analysis of
coherent harmonic radiation from individual or two consecutive undulator segments, the so-called coherent
photon beam based diagnostic, is proposed for undulator alignment and commissioning in seeded FELs.
The preliminary experimental results at the Shanghai deep ultraviolet FEL test facility are presented. It
shows that the proposed method is effective and convenient in the electron beam trajectory control, the
undulator magnetic gap verification, and the phase match between two undulator segments.
In this paper, a fully coherent radiation option with controllable
polarization is proposed for Shanghai deep ultraviolet free electron laser
(FEL) test facility. Intensive start-to-end simulation suggests that, the two
crossed planar undulators which generate the horizontal and vertical linear
polarized FEL respectively, should be placed as close as possible for avoiding
the polarization performance degradation of the final combined FEL radiation.
With the existence of the phase-shifter between the two crossed radiators,
Fourier-Transform-Limited output radiation with 100 nJ order pulse energy, 5 ps
full pulse length and circular polarization degree above 90% could be achieved.
