The resolution of the system given by Maxwell's equations and Vlasov equation in three dimensions can describe all the phenomena of interest for laser wakefield acceleration, with few exceptions ...(e.g. ionization). Such arduous task can be numerically completed using Particle in Cell (PIC) codes, where the plasma is sampled by an ensemble of macroparticles and the electromagnetic fields are defined on a computational grid. However, the resulting three dimensional PIC simulations require substantial resources and often yield a larger amount of information than the one necessary to study a particular aspect of a phenomenon. Reduced models, i.e. models of the Maxwell-Vlasov system taking into account approximations and symmetries, are thus of fundamental importance for preliminary studies and parametric scans. In this work, the implementation of one of these models in the code SMILEI, an envelope description of the laser-plasma interaction with cylindrical symmetry, is described.
We report on the first experimental characterization of a gamma-ray spectrometer designed to spectrally resolve high-flux photon beams with energies in the GeV range. The spectrometer has been ...experimentally characterized using a bremsstrahlung source obtained at the Apollon laser facility during the interaction of laser-wakefield accelerated electron beams (maximum energy of 1.7 GeV and overall charge of 207±62 pC) with a 1 mm thick tantalum target. Experimental data confirms the possibility of performing single-shot measurements, without the need for accumulation, with a high signal-to-noise ratio. Scaling the results to photons in the multi-GeV range suggests the possibility of achieving percent-level energy resolution as required, for instance, by the next generation of experiments in strong-field quantum electrodynamics.
The optimization and advanced study of a laser-plasma electron injector are presented based on a truncated ionization injection scheme for high quality beam production. The smilei code is used with ...laser envelope approximation and a low number of particles per cell to reach computation time performances enabling the production of a large number of accelerator configurations. The developed and tested workflow is a possible approach for the production of a large dataset for laser-plasma accelerator optimization. A selection of functions of merit used to grade generated electron beams is discussed. Among the significant number of configurations, two specific working points are presented in detail. All data generated are left open to the scientific community for further study and optimization.
The Horizon 2020 Project EuPRAXIA (“European Plasma Research Accelerator with eXcellence In Applications”) is preparing a conceptual design for a highly compact and cost-effective European facility ...with multi-GeV electron beams using plasma as the acceleration medium. The design includes two user areas: one for FEL science and one for High Energy Physics (HEP) detector development and other pilot applications. The accelerator facility will be based on a laser and/or a beam driven plasma acceleration approach. This contribution introduces layout considerations of the future plasma accelerator facilities in the context of EuPRAXIA. It compares conventional and novel plasma accelerator facility requirements and presents potential layouts for the future site. Together with performance analysis, cost effectiveness, and targeted user cases of the individual configurations, such layout studies will later enable a ranking of potential configurations. Based on this information the optimal combination of technologies will be defined for the 2019 conceptual design report of the EuPRAXIA facility.
Optimal regimes and physical processes at work are identified for the first round of laser wakefield acceleration experiments proposed at a future CILEX facility. The Apollon-10P CILEX laser, ...delivering fully compressed, near-PW-power pulses of sub-25 fs duration, is well suited for driving electron density wakes in the blowout regime in cm-length gas targets. Early destruction of the pulse (partly due to energy depletion) prevents electrons from reaching dephasing, limiting the energy gain to about 3 GeV. However, the optimal operating regimes, found with reduced and full three-dimensional particle-in-cell simulations, show high energy efficiency, with about 10% of incident pulse energy transferred to 3 GeV electron bunches with sub-5% energy spread, half-nC charge, and absolutely no low-energy background. This optimal acceleration occurs in 2 cm length plasmas of electron density below 1018 cm-3. Due to their high charge and low phase space volume, these multi-GeV bunches are tailor-made for staged acceleration planned in the framework of the CILEX project. The hallmarks of the optimal regime are electron self-injection at the early stage of laser pulse propagation, stable self-guiding of the pulse through the entire acceleration process, and no need for an external plasma channel. With the initial focal spot closely matched for the nonlinear self-guiding, the laser pulse stabilizes transversely within two Rayleigh lengths, preventing subsequent evolution of the accelerating bucket. This dynamics prevents continuous self-injection of background electrons, preserving low phase space volume of the bunch through the plasma. Near the end of propagation, an optical shock builds up in the pulse tail. This neither disrupts pulse propagation nor produces any noticeable low-energy background in the electron spectra, which is in striking contrast with most of existing GeV-scale acceleration experiments.
Luminosity measurement in H1 Frisson, T.; Boudry, V.; Specka, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2011, Letnik:
640, Številka:
1
Journal Article
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The HERA luminosity was determined by measuring the flux of bremsstrahlung photons emitted at zero degree off electrons in the field of protons in the interaction region. After the HERA upgrade, the ...H1 Collaboration developed a new luminosity system which measured all the emitted photons in a bunch crossing. We describe the expression of this photon flux in the luminosity detector which is used in the simulation of the detector. The total energy method, based on the measurement of the bremsstrahlung photon energy flux in the calorimeter, is the standard method for the off-line luminosity measurement. In this study, we propose a new method to calculate the luminosity. This new method is based on the shape of the bremsstrahlung photon energy spectrum measured in the luminosity detector. The two methods are compared. A good agreement is observed.
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