Density downramp injection has been demonstrated to be an elegant and efficient approach for generating high-quality electron beams in laser wakefield accelerators.Recent studies have demonstrated the possibilities of...Density downramp injection has been demonstrated to be an elegant and efficient approach for generating high-quality electron beams in laser wakefield accelerators.Recent studies have demonstrated the possibilities of generating electron beams with charges ranging from tens to hundreds of picocoulombs while maintaining good beam quality.However,the plasma and laser parameters in these studies have been limited to specific ranges or attention has been focused on separate physical processes such as beam loading,which affects the uniformity of the accelerating field and thus the energy spread of the trapped electrons,the repulsive force from the rear spike of the bubble,which reduces the transverse momentum P⊥of the trapped electrons and results in small beam emittance,and the laser evolution when traveling in the plasma.In this work,we present a comprehensive numerical study of downramp injection in the laser wakefield,and we demonstrate that the current profile of the injected electron beam is directly correlated with the density transition parameters,which further affects the beam charge and energy evolution.By fine-tuning the plasma density parameters,electron beams with high charge(up to several hundreds of picocoulombs)and low energy spread(around 1%FWHM)can be obtained.All these results are supported by large-scale quasi-threedimensional particle-in-cell simulations.We anticipate that the electron beams with tunable beam properties generated using this approach will be suitable for a wide range of applications.展开更多
The development of plasma-based accelerators has enabled the generation of very high brightness electron bunches of femtosecond duration,micrometer size and ultralow emittance,crucial for emerging applications includi...The development of plasma-based accelerators has enabled the generation of very high brightness electron bunches of femtosecond duration,micrometer size and ultralow emittance,crucial for emerging applications including ultrafast detection in material science,laboratory-scale free-electron lasers and compact colliders for high-energy physics.The precise characterization of the initial bunch parameters is critical to the ability to manipulate the beam properties for downstream applications.Proper diagnostic of such ultra-short and high charge density laser-plasma accelerated bunches,however,remains very challenging.Here we address this challenge with a novel technique we name as femtosecond ultrarelativistic electron microscopy,which utilizes an electron bunch from another laser-plasma accelerator as a probe.In contrast to conventional microscopy of using very low-energy electrons,the femtosecond duration and high electron energy of such a probe beam enable it to capture the ultra-intense space-charge fields of the investigated bunch and to reconstruct the charge distribution with very high spatiotemporal resolution,all in a single shot.In the experiment presented here we have used this technique to study the shape of a laser-plasma accelerated electron beam,its asymmetry due to the drive laser polarization,and its beam evolution as it exits the plasma.We anticipate that this method will significantly advance the understanding of complex beam-plasma dynamics and will also provide a powerful new tool for real-time optimization of plasma accelerators.展开更多
Technology based on high-peak-power lasers has the potential to provide compact and intense radiation sources for a wide range of innovative applications.In particular,electrons that are accelerated in the wakefield o...Technology based on high-peak-power lasers has the potential to provide compact and intense radiation sources for a wide range of innovative applications.In particular,electrons that are accelerated in the wakefield of an intense laser pulse oscillate around the propagation axis and emit X-rays.This betatron source,which essentially reproduces the principle of a synchrotron at the millimeter scale,provides bright radiation with femtosecond duration and high spatial coherence.However,despite its unique features,the usability of the betatron source has been constrained by its poor control and stability.In this article,we demonstrate the reliable production of X-ray beams with tunable polarization.Using ionization-induced injection in a gas mixture,the orbits of the relativistic electrons emitting the radiation are reproducible and controlled.We observe that both the signal and beam profile fluctuations are significantly reduced and that the beam pointing varies by less than a tenth of the beam divergence.The polarization ratio reaches 80%,and the polarization axis can easily be rotated.We anticipate a broad impact of the source,as its unprecedented performance opens the way for new applications.展开更多
基金supported by the Fondation Jacques Toledano and the Schwartz-Reisman Center for Intense Laser Physics,and by ERC PoC Vherapy and EIC ebeam4therapy grants.
文摘Density downramp injection has been demonstrated to be an elegant and efficient approach for generating high-quality electron beams in laser wakefield accelerators.Recent studies have demonstrated the possibilities of generating electron beams with charges ranging from tens to hundreds of picocoulombs while maintaining good beam quality.However,the plasma and laser parameters in these studies have been limited to specific ranges or attention has been focused on separate physical processes such as beam loading,which affects the uniformity of the accelerating field and thus the energy spread of the trapped electrons,the repulsive force from the rear spike of the bubble,which reduces the transverse momentum P⊥of the trapped electrons and results in small beam emittance,and the laser evolution when traveling in the plasma.In this work,we present a comprehensive numerical study of downramp injection in the laser wakefield,and we demonstrate that the current profile of the injected electron beam is directly correlated with the density transition parameters,which further affects the beam charge and energy evolution.By fine-tuning the plasma density parameters,electron beams with high charge(up to several hundreds of picocoulombs)and low energy spread(around 1%FWHM)can be obtained.All these results are supported by large-scale quasi-threedimensional particle-in-cell simulations.We anticipate that the electron beams with tunable beam properties generated using this approach will be suitable for a wide range of applications.
基金This work was supported by The Schwartz/Reisman Center for Intense Laser Physics,by a research grant from the Benoziyo Endowment Fund for the Advancement of Science,by the Israel Science Foundation,Minerva,Wolfson Foundation,the Schilling Foundation,R.Lapon,Dita&Yehuda Bronicki,and by the Helmholtz association.The simulations were carried out at the Weizmann Institute’s EXAscale Cluster(WEXAC).Y.W.would like to thank Aaron Liberman for improving the context,and thank Dr.Igor A.Andriyash from Laboratoire d’Optique Appliquée and Prof.Wei Lu from Tsinghua University for helpful discussions.
文摘The development of plasma-based accelerators has enabled the generation of very high brightness electron bunches of femtosecond duration,micrometer size and ultralow emittance,crucial for emerging applications including ultrafast detection in material science,laboratory-scale free-electron lasers and compact colliders for high-energy physics.The precise characterization of the initial bunch parameters is critical to the ability to manipulate the beam properties for downstream applications.Proper diagnostic of such ultra-short and high charge density laser-plasma accelerated bunches,however,remains very challenging.Here we address this challenge with a novel technique we name as femtosecond ultrarelativistic electron microscopy,which utilizes an electron bunch from another laser-plasma accelerator as a probe.In contrast to conventional microscopy of using very low-energy electrons,the femtosecond duration and high electron energy of such a probe beam enable it to capture the ultra-intense space-charge fields of the investigated bunch and to reconstruct the charge distribution with very high spatiotemporal resolution,all in a single shot.In the experiment presented here we have used this technique to study the shape of a laser-plasma accelerated electron beam,its asymmetry due to the drive laser polarization,and its beam evolution as it exits the plasma.We anticipate that this method will significantly advance the understanding of complex beam-plasma dynamics and will also provide a powerful new tool for real-time optimization of plasma accelerators.
基金the Agence Nationale pour la Recherche through the FENICS Project No.ANR-12-JS04-0004-01the Agence Nationale pour la Recherche through the FEMTOMAT Project No.ANR-13-BS04-0002+4 种基金the X-Five project(Contract No.339128)the LUCELX project(ANR-13-BS04-0011)the EuCARD2/ANAC2 EC FP7 project(Contract No.312453)the GARC project 15-03118Ssupport from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No.654148 Laserlab-Europe.
文摘Technology based on high-peak-power lasers has the potential to provide compact and intense radiation sources for a wide range of innovative applications.In particular,electrons that are accelerated in the wakefield of an intense laser pulse oscillate around the propagation axis and emit X-rays.This betatron source,which essentially reproduces the principle of a synchrotron at the millimeter scale,provides bright radiation with femtosecond duration and high spatial coherence.However,despite its unique features,the usability of the betatron source has been constrained by its poor control and stability.In this article,we demonstrate the reliable production of X-ray beams with tunable polarization.Using ionization-induced injection in a gas mixture,the orbits of the relativistic electrons emitting the radiation are reproducible and controlled.We observe that both the signal and beam profile fluctuations are significantly reduced and that the beam pointing varies by less than a tenth of the beam divergence.The polarization ratio reaches 80%,and the polarization axis can easily be rotated.We anticipate a broad impact of the source,as its unprecedented performance opens the way for new applications.