Values Of Energy Spread Research Articles

Experimental characterization of the optical klystron effect to measure the intrinsic energy spread of high-brightness electron beams

The intrinsic energy spread of electron beams needs to be measured to characterize and optimize high-brightness electron beam sources such as those driving x-ray free-electron lasers (FELs). We demonstrate the use of the optical klystron effect as a precise and high-resolution method to measure the electron beam energy spread. The optical klystron setup consists of undulator modules and magnetic chicanes placed between them. The energy spread is found by measuring the radiation power produced in the undulators as a function of the chicanes’ strengths. High resolution and simplicity are the advantages of this approach, in contrast to the standard method, which measures the longitudinal phase space of the electron beam with a transverse deflector. The demonstration was performed at Athos, the soft x-ray FEL beamline of SwissFEL, for which we measured energy spreads below 1 MeV at a central beam energy of 3.4 GeV. We have verified the consistency of the method for different parameters (radiation wavelengths, undulator polarization configurations, and electron bunch durations) and we have benchmarked it against the standard measurement approach using a transverse deflector. Our results confirm the optical klystron as a valid approach to measure the electron beam energy spread. The method can be especially useful to reconstruct low energy spread values, where the conventional approach may be resolution limited, such as in ultra high-brightness radiofrequency photoinjectors or plasma sources, or when transverse deflectors are not available. Published by the American Physical Society 2024

Coherence properties of the high-energy fourth-generation X-ray synchrotron sources.

An analysis of the coherence properties of the fourth-generation high-energy storage rings with emittance values of 10 pm rad is performed. It is presently expected that a storage ring with these low emittance values will reach diffraction limit at hard X-rays. Simulations of coherence properties were performed with the XRT software and an analytical approach for different photon energies from 500 eV to 50 keV. It was demonstrated that a minimum photon emittance (diffraction limit) reached at such storage rings is λ/2π. Using mode decomposition it is shown that, for the parameters of the storage ring considered in this work, the diffraction limit will be reached for soft X-ray energies of 500 eV. About ten modes will contribute to the radiation field at 12 keV photon energy and even more modes give a contribution at higher photon energies. Energy spread effects of the electron beam in a low-emittance storage ring were analysed in detail. Simulations were performed at different relative energy spread values from zero to 2 × 10-3. A decrease of the degree of coherence with an increase of the relative energy spread value was observed. This analysis shows that, to reach the diffraction limit for high photon energies, electron beam emittance should go down to 1 pm rad and below.

Quantum theory for 1D X-ray free electron laser

Classical 1D X-ray Free Electron Laser (X-ray FEL) theory has stood the test of time by guiding FEL design and development prior to any full-scale analysis. Future X-ray FELs and inverse-Compton sources, where photon recoil approaches an electron energy spread value, push the classical theory to its limits of applicability. After substantial efforts by the community to find what those limits are, there is no universally agreed upon quantum approach to design and development of future X-ray sources. We offer a new approach to formulate the quantum theory for 1D X-ray FELs that has an obvious connection to the classical theory, which allows for immediate transfer of knowledge between the two regimes. We exploit this connection in order to draw quantum mechanical conclusions about the quantum nature of electrons and generated radiation in terms of FEL variables.

Innovative X–γ ray sources based on laser-produced plasmas

The paper concerns with the dynamics and the emitted radiation of electrons undergoing betatron oscillations in laser-produced plasmas. The topic is relevant for a reliable interpretation of data will be obtained in forthcoming experiments in the LASER facility of the National Laboratories of Frascati (LNF) of the National Institute for Nuclear Physics (INFN). The blowout regime will be considered, which makes the electrons reaching very high energies by providing impressive accelerating gradients while keeping a low energy spread value. The accident that the betatron emission occurs meanwhile electrons gain energy is also considered here.

The energy spread of a LaB6 cathode operated in the virtual source mode

The LaB6 cathode has been the brightest thermionic source used in microprobe applications requiring longer lifetime [1-2]. It is x100 lower in brightness than thermal field emitters (TFE) ca Zr/W (100) [3]. There are attractive similarities between these cathodes in terms of work function and operating temperature that are worth considering. Major differences include their respective source sizes (>10μm vs 30nm) and energy spread of 1-2 eV vs 0.6-0.7eV for the LaB6 and TFE, respectively [4,3].We report here on the experimental measurement of the energy spread of a LaB6 cathode operated in the virtual source mode. The cathode used has an end-form measuring 15μm. Total energy spread values obtained using a dedicated electron energy analyser shows values of 0.4eV-0.7eV, significantly lower than typical values in the thermionic mode of 1-2eV.

Formation of Accelerated Particle Beam in Isochronous Cyclotron

In the literature there is usually considered a dependence of the one of main beam parameters the value of energy spread, ∆E/E, on cyclotron characteristics for magnetic eld by form closed to isochronous one [1]. Since the output of ion beams from considered installation is realized in decreasing eld, there was carried out an estimation of energetic spread of the beam with nite phase width ∆φ in case of one-revolution output for real magnetic eld that has a decreasing area.

Spectral properties of two frequency harmonic undulator radiations and effect of energy spread

Abstract The dynamics of complex spectral properties of two frequency harmonic undulator radiations along on and off axis has been analytically investigated using the techniques of generalized Bessel functions. The relativistic electron beams with non negligible energy spread results in degradation in brightness and gain. The effect of energy spread on two frequency harmonic undulator (TFHU) radiations and on axis gain has been analyzed. Maximum acceptable r.m.s. value of energy spread has been determined to support the complex spectral pattern of radiation and gain.

Effect of emittance and energy spread on a free-electron laser in the gain-focusing regime

A free-electron laser operating in the gain-focusing regime is discussed. The variation of growth rate, radius of curvature of wave fronts, filling factor and efficiency with emittance, and energy spread is derived. The reults, which are based on the Vlasov-Maxwell system of equations, are obtained by minimizing a variational functional. When plotted as a function of emittance, the efficiency at maximum growth rate peaks at a nonzero value of emittance. For small values of energy spread, the efficiency at maximum growth rate increases with energy spread, in contrast to intuitive expectations.

On the beam energy spread of a pulsed Van De Graaf acceletator

The beam energy spread of the 2.5 MeV Van de Graaff accelerator at the Research Institute of National Defence has been measured by investigating the gamma-ray yield from the reaction 13C(p,γ) 14N at the 1.75 MeV resonance. The observed values of energy spread (fwhm) were 1.4% for continuous beam, 1.5% for internally pulsed beam (10 ns pulses) and 3.4% for a pulsed and bunched beam (1 ns pulses).