Sebastian Lorenz, Gabriele Grittani, Leonardo Goncalves, Marcel Lamač, Carlo Maria Lazzarini, Jiří Limpouch, Michal Nevrkla, Marek Raclavský, Alžběta Špádová, Petr Valenta, Illia Zymak, Sergei Bulanov
The extremely high electric fields sustainable by a plasma make the Laser Wakefield Acceleration (LWFA) the most compact technique to generate very highly relativistic electron beams in the GeV regime. The limited repetition rate and low efficiency of this technology has, to date, prevented to unleash its full potential as a unique source for basic research, biomedical applications and high flux sources of secondary radiations as hard X-rays and gamma-rays. In very recent years different works show a new research direction on electron acceleration at 1 kHz repetition rate.
In this talk I will show the laser-driven acceleration of unprecedented, collimated (2 mrad) and quasi-monoenergetic (ΔE/E = 25%) electron beams with energy up to 50 MeV at 1 kHz repetition rate. The laser driver is the in-house developed L1-Allegra multi-cycle (15 fs) 1 kHz OPCPA system, operating at 26 mJ (1.7 TW).
Said innovative results have been achieved in the new Laser Wakefield ALFA platform for user experiments developed at ELI-Beamlines.
The scalability of the driver laser technology and the electron beams reported in this work pave the way towards developing high brilliance X-ray sources for medical imaging, innovative devices for brain cancer treatment and represent a step forward to the realization of a kHz GeV electron beamline.
The OPCPA-based high energy 1 kHz laser system, operating at 820 nm provides exceptionally good contrast 15 fs pulses for a variety of user experiments at ELI Beamlines. The system is gradually upgraded to meet the demand of high energy high average power ultrashort pulse sources for the research in fields of HHG, X-ray generation and wake-field electron acceleration. The current parameters of the system are presented together a glimpse on recently performed state-of-the-art experiments.
We review a number of instruments employed in a high-intensity J-KAREN-P laser-solid interaction experiment and discuss the applicability of the diagnostics to the best target position determination with a ~10 μm accuracy, while the focal spot size was ~1 μm and peak intensity was up to 7×1021 W/cm2. We discuss both front- and back-side diagnostics, some of them operated in the infrared, visible and ultraviolet ranges, while others in the extreme ultraviolet, soft X-ray and gamma-ray ranges. We found that the applicability of some of the instruments to the best at-focus target position determination depends on the thickness of the target.
Electron-laser colliders are a unique tool to investigate different fundamental phenomena, as for example the Breit-Wheeler process. Several experiments are working in this direction as of now, both based on conventional electron accelerator technology or on all-optical schemes.
In the landscape of high power laser facilities, ELI-Beamlines has two unique lasers which have the potential to enable laser-electron collisions at unprecedented parameters: L3-HAPLS (30 J, 30 fs, 10 Hz) and L4-Aton (1.5 kJ, 150 fs, 100s shots/day). In ELI-ELBA, the L3 laser pulses are split in two by a 50:50 wavefront splitting mirror. The central part of the beam is focused by a 10 meter focal length off-axis parabola into a gas jet to generate GeV electron beams by laser wakefield acceleration. The outer part of the beam is focused on the electron beam by a f/1.5 off-axis parabola with a hole.
The installation of ELI-ELBA and the results of the technical commissioning at low-power (L3 front-end) will be presented, along with the experiments proposed by the user community. The designed upgrade of ELI-ELBA for 10 PW experiments will be also presented.
The laser wakefield acceleration program at ELI-Beamlines benefits from the future availability of four unique high power laser systems that make possible the investigation of LWFA in a broad range of parameters, ranging from mJ to kJ in pulse energy.
The experiments driven by the PW-class laser systems L3-HAPLS (Ti:Sapph, 30 J, 30 fs, 10 Hz) and L4-Aton (Nd:glass, 1.5 kJ, 150 fs, 0.01 Hz) are performed at the ELI-ELBA beamline, and aim at the counter-propagation of laser-accelerated GeV electron beams with high intensity laser pulses. These experiments are designed to study novel regimes of electromagnetic field interaction with matter and quantum vacuum. The flagship experiment of ELI-ELBA is the experimental measurement of synergic Cherenkov-Compton radiation, which will reveal the properties of the vacuum predicted by nonlinear quantum electrodynamics and will require the operation of L3-HAPLS and L4-Aton at full power.
The LWFA experiments driven by the TW-class high rep-rate laser systems L1-Allegra (100 mJ, 15 fs, 1 kHz) and L2-Duha (>3J, 25 fs, 50 Hz) are oriented towards laser-driven FEL development and applications in the biomedical field, and to investigation of interaction of high power lasers with near critical density plasmas.
In the presentation, the actual status of the ELI-ELBA GeV electron beamline will be presented, along with the schedule leading to the commissioning and full operations. The activity in the field of high repetition rate LWFA will be also presented, including recent theoretical and simulation results, and the description of the experiments planned. Finally, recent design work towards a laser-driven VHEE radiotherapy device will be presented.
Using analytical methods and computer simulations, we investigate physical processes which lead to the formation of ring-shaped electromagnetic and electron structures in laser-plasma interaction. We observe that as the intense laser pulse excites a nonlinear Langmuir wave in an underdense plasmas, a significant portion of the pulse is refracted outwards the propagation direction due to the interactions with thin, high-density electron walls surrounding the wave cavities. Because of the radial symmetry, the refracted light forms a distinct electromagnetic ring that encircles the driver pulse. The efficiency of the energy transfer to the electromagnetic ring is relatively high, so that the ring can generate its own Langmuir wave and trigger the electron self-injection, which results in a ring-shaped beam of high-energy electrons. The properties of the ring-shaped electromagnetic and electron beams depend on the parameters of the Langmuir wave cavity walls, thus they can be controlled by tuning the parameters of the laser and plasma. The ring structures could be applied as a drivers for acceleration of positively charged particles, or as a diagnostic to determine regimes and the overall efficiency of the laser-wakefield accelerator.
Combination of revolutionary high-repetition-rate high-power laser technology and the latest achievements in laser-plasma accelerators (LPAs) opens the way to develop a new generation of laser-driven compact free-electron lasers (FEL). The LPA electron beam brightness is extremely high due to a low normalized emittance (less than 0.5 µm) and high peak current (multi kA), resulting from an ultra-short e-beam duration (few fsec), which makes such beam extremely attractive for the production of high power pulses of the coherent photon radiation. In the frame of this report, we overview the laser-driven FEL research program at ELI-Beamlines (near Prague, Czech Republic), which aims to demonstrate the self-amplified spontaneous emission (SASE) regime with a generation of the coherent photon radiation starting from the extreme ultraviolet wavelength range. A possible extension of this research program to the X-ray FEL regime will be discussed.
Laser wakefield acceleration (LWFA) using high repetition rate mJ-class laser systems brings unique opportunities for a broad range of applications. In order to meet the conditions required for the electron acceleration with lasers operating at lower energies, one has to use high density plasmas and ultrashort pulses. In the case of a few-cycle pulse, the dispersion and the carrier envelope phase effects can no longer be neglected. In this work, the properties of the wake waves generated by ultrashort pulse lasers in near-critical density plasmas are investigated. The results obtained may lead to enhancement of the quality of LWFA electron beams using kHz laser systems.
KEYWORDS: High power lasers, Plasma, Calibration, Electron beams, Monte Carlo methods, Diagnostics, Particles, Lead, Sensors, Diagnostic tests, Synchrotrons, Electronics
HELL is the high energy electron beamline under development at ELI-Beamlines, which is expected to produce GeV electrons at high repetition rate. The aim of HELL is dual: to improve the performances of the laser electron accelerator, and to deliver stable beams for external users. In this work, we present the recent developments towards the delivery of stable and calibrated beams for external users. The design of the HELL User Station will be presented and discussed along with simulations and experimental data collected in different facilities.
The quadrupole lens free multiple profile emittance measurement method is an adaptation of the standard multiple profile monitor method for electron beam emittance measurement which was tested at PW laser system. This single shot technique allows to obtain the emittance from beam profile radii fit by means of Twiss (Courant-Snyder) parameters. Lanex scintillating screens were used as profile monitors due to their high yield of visible photons. However, on the other hand, the screen is a source of multiple Coulomb scattering which can influence the beam profile on the following screens at relatively low electron energies. Nevertheless, the contribution of the multiple scattering can be effectively subtracted from the signal by e.g. Bayes unfolding. For high energy beams (E > 0.5 GeV), the multiple scattering contribution is negligible. The presented diagnostics is easy to be implemented into standard experimental setups without any special requests for alignment procedure. Moreover, it can be useful in the optimization phase of the laser plasma accelerator where beam fundamental parameters (energy, energy spread, divergence, pointing) typically fluctuate shot-to- shot.
KEYWORDS: Electron beams, Electron transport, Magnetism, Spectroscopy, Plasma, Physics, Monte Carlo methods, Radiography, Radiotherapy, Optical simulations
In the framework of the ELI-Beamlines project, the HELL (High energy ELectron by Laser) platform will host an electron beamline with a dual aim: to explore innovative concepts of laser driven electron acceleration and to deliver a stable and reliable electron beam to external users, according to their specific needs. Because of this, it is crucial to identify the possible applications and their respective range of parameters. In order to accomplish this goal, Monte Carlo simulations of electron radiography and radiotherapy are performed and discussed. Once identified those parameter spaces, a beam transport line is studied and presented for each energy range. Finally, beam diagnostics are discussed.
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