Beam dynamics of realistic bunches at the injector section of the European X-ray Free-Electron Laser

Chen, Ye; Zagorodnov, Igor; Dohlus, M.

doi:10.1103/physrevaccelbeams.23.044201

Cited by 15 publications

(13 citation statements)

References 20 publications

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“…Moreover, aging of accelerator components affects the long-term operation of a facility but is generally not included in simulations. As a result, it is extremely challenging to achieve good agreement between simulations and measurements for a large range of machine operation parameters, even by exploiting complicated physical models [15]. Furthermore, it can be prohibitively expensive to collect a large amount of high-resolution simulation data [16].…”

Section: Introductionmentioning

confidence: 99%

High-Fidelity Prediction of Megapixel Longitudinal Phase-Space Images of Electron Beams Using Encoder-Decoder Neural Networks

Zhu

Chen²,

Brinker³

et al. 2021

Phys. Rev. Applied

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Modeling of large-scale research facilities is extremely challenging due to complex physical processes and engineering problems. Here, we adopt a data-driven approach to model the longitudinal phase-spacediagnostic beamline at the photoinector of the European XFEL with an encoder-decoder neural-network model. A deep convolutional neural network (decoder) is used to build images, measured on the screen, from a small feature map generated by another neural network (encoder). We demonstrate that the model, trained only with experimental data, can make high-fidelity predictions of megapixel images for the longitudinal phase-space measurement without any prior knowledge of photoinjectors or electron beams. The prediction significantly outperforms existing methods. We also show the scalability and interpretability of the model by sharing the same decoder with more than one encoder, used for different setups of the photoinjector, and propose a pragmatic way to model a facility with various diagnostics and working points. This opens the door to a way of accurately modeling a photoinjector using neural networks and experimental data. The approach can possibly be extended to the whole accelerator and even other types of scientific facility.

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Section: Introductionmentioning

confidence: 99%

High-Fidelity Prediction of Megapixel Longitudinal Phase-Space Images of Electron Beams Using Encoder-Decoder Neural Networks

Zhu

Chen²,

Brinker³

et al. 2021

Phys. Rev. Applied

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“…By attenuation of the pulse energy, the laser system can extract different bunch charges from the cathode [36]. Along with the aforementioned variability in the imaging system of the laser, the emittance growth at a fixed charge can be minimized by optimization of transverse laser pulse shape via modeling of the photoemission process [37,38]. In addition, a typical surface roughness of the cesium-telluride photocathode produced using the present recipe is about 10 nm.…”

Section: Near-cathode Particle Dynamicsmentioning

confidence: 97%

“…In this section, the performance of the EuXFEL injector [34,38] [as shown in Figure 1b] with the currently existing cathode laser pulse shaping capabilities, intrinsic emittance of the cathode, and position of the beamline components is studied for varying peak accelerating gradients at the cathode position. The gun solenoid strength, operation phase of the gun and rms size of the cathode laser spot are considered for the optimization.…”

Section: Budgeting Emittance At Multiple Accelerating Gradients At the Cathodementioning

confidence: 99%

Perspectives towards Sub-Ångström Working Regime of the European X-ray Free-Electron Laser with Low-Emittance Electron Beams

et al. 2021

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Sub-ångström working regime refers to a working state of free-electron lasers which allows the generation of hard X-rays at a photon wavelength of 1 ångström and below, that is, a photon energy of 12.5 keV and above. It is demonstrated that the accelerators of the European X-ray Free-Electron Laser can provide highly energetic electron beams of up to 17.5 GeV. Along with long variable-gap undulators, the facility offers superior conditions for exploring self-amplified spontaneous emission (SASE) in the sub-ångström regime. However, the overall FEL performance relies quantitatively on achievable electron beam qualities through a kilometers-long accelerator beamline. Low-emittance electron beam production and the associated start-to-end beam physics thus becomes a prerequisite to dig in the potentials of SASE performance towards higher photon energies. In this article, we present the obtained results on electron beam qualities produced with different accelerating gradients of 40 MV/m–56 MV/m at the cathode, as well as the final beam qualities in front of the undulators via start-to-end simulations considering realistic conditions. SASE studies in the sub-ångström regime, using optimized electron beams, are carried out at varied energy levels according to the present state of the facility, that is, a pulsed mode operating with a 10 Hz-repetition 0.65 ms-long bunch train energized to 14 GeV and 17.5 GeV. Millijoule-level SASE intensity is obtained at a photon energy of 25 keV at 14 GeV electron beam energy using a gain length of about 7 m. At 17.5 GeV, half-millijoule lasing is achieved at 40 keV. Lasing at up to 50 keV is demonstrated with pulse energies in the range of a few hundreds and tens of microjoules with existing undulators and currently achievable electron beam qualities.

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“…In the experiment, the RF gun and the cathode laser mimic the 250 pC working point of the European XFEL injector [26,34,35]. The photoelectron beam is generated by UV laser illuminating the Cs 2 Te cathode.…”

Section: Measurementsmentioning

confidence: 99%

Slice energy spread measurement in the low energy photoinjector

Qian,

Krasilnikov,

Lueangaramwong

et al. 2022

Preprint

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Slice energy spread is one of the key parameters in free electron laser optimizations, but its accurate measurement is not straightforward. Two recent studies from high energy (>100 MeV) photoinjectors at SwissFEL and European XFEL have reported much higher slice energy spread than expected at their XFEL working points (200 -250 pC). In this paper, a new method for measuring slice energy spread at a lower beam energy (∼20 MeV) is proposed and demonstrated at the PhotoInjector Test facility at DESY Zeuthen (PITZ), and the results for 250 pC and 500 pC are much lower than those measured at high energy injectors.

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Beam dynamics of realistic bunches at the injector section of the European X-ray Free-Electron Laser

Cited by 15 publications

References 20 publications

High-Fidelity Prediction of Megapixel Longitudinal Phase-Space Images of Electron Beams Using Encoder-Decoder Neural Networks

High-Fidelity Prediction of Megapixel Longitudinal Phase-Space Images of Electron Beams Using Encoder-Decoder Neural Networks

Perspectives towards Sub-Ångström Working Regime of the European X-ray Free-Electron Laser with Low-Emittance Electron Beams

Slice energy spread measurement in the low energy photoinjector

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