Electron energy increase in a laser wakefield accelerator using longitudinally shaped plasma density profiles
Constantin Aniculaesei, Vishwa Bandhu Pathak, Hyung Taek Kim, Kyung Hwan Oh, Byung Ju Yoo, Enrico Brunetti, Yong Ha Jang, Calin Ioan Hojbota, Junghun Shin, Jeon… 展开作者
Constantin Aniculaesei, Vishwa Bandhu Pathak, Hyung Taek Kim, Kyung Hwan Oh, Byung Ju Yoo, Enrico Brunetti, Yong Ha Jang, Calin Ioan Hojbota, Junghun Shin, Jeong Ho Jeon, Seongha Cho, Myung Hoon Cho, Jae Hee Sung, Seong Ku Lee, Björn Manuel Hegelich, Chang Hee Nam
The phase velocity of the wakefield of a laser wakefield accelerator can, theoretically, be manipulated by shaping the longitudinal plasma density profile, thus controlling the parameters of the generated electron beam. We present an experimental method where using a series of shaped longitudinal plasma density profiles we increased the mean electron peak energy by more than 50%, from 174.8 +/- 1.3 MeV to 262 +/- 9.7 MeV and the maximum peak energy from 182.1 MeV to 363.1 MeV. The divergence follows closely the change of mean energy and decreases from 58.95 +/- 0.45 mrad to 12.63 +/- 1.17 mrad along the horizontal axis and from 35.23 +/- 0.27 mrad to 8.26 +/- 0.69 mrad along the vertical axis. Particle-in-cell simulations show that a ramp in a plasma density profile can affect the evolution of the wakefield, thus qualitatively confirming the experimental results. The presented method can increase the electron energy for a fixed laser power and at the same time offer an energy tunable source of electrons.
Ion motion in plasma wakefield accelerators can cause temporal increase of the longitudinal electric field shortly before the wave breaks. The increase is caused by re-distribution of the wave energy in transverse direction and may be important for correct interpretation of experimental results and acceleration of high-quality beams.
A classical model of radiation reaction for the betatron oscillation of an electron in a plasma wakefield accelerator is presented. The maximum energy of the electron due to the longitudinal radiation reaction is found, and the betatron oscillation damping due to both the longitudinal and transverse radiation reaction effects is analyzed. Both theoretical and numerical solutions are shown with good agreements. The regime that the quantum radiation takes effect is also discussed. This model is important for designing future plasma based super accelerators or colliders.
A new scheme for injection and acceleration of electrons in wakefield accelerators is suggested based on the co-action of a laser pulse and an electron beam. This synergy leads to stronger wakefield generation and higher energy gain in the bubble regime. The strong deformation of the whole bubble leads to electron self-injection at lower laser powers and lower plasma densities. To predict the practical ranges of electron beam and laser pulse parameters an interpretive model is proposed. The effects of altering the initial electron beam position on self-trapping of plasma electrons are studied.…
Propagation distances of intense laser pulses and high-charge electron beams through the plasma are, respectively, limited by diffraction and self-deceleration. This imposes severe constraints on the performance of the two major advanced accelerator concepts: laser and plasma wakefield accelerators. Using numerical simulations, we demonstrate that when the two beams co-propagate in the plasma, they can interact synergistically and extend each other's travel distances. The key interactions responsible for the synergy are found to be laser channeling by the electron bunch, and direct laser accel…
The effect of an external transverse magnetic field on ionization injection of electrons in a laser wakefield accelerator (LWFA) is investigated by theoretical analysis and particle-in-cell simulations. On application of a few tens of Tesla magnetic field, both the electron trapping condition and the wakefield structure changes significantly such that injection occurs over a shorter distance and at an enhanced rate. Furthermore, beam loading is compensated for, as a result of the intrinsic trapezoidal-shaped longitudinal charge density profile of injected electrons. The nonlinear ionization in…
We report on the depletion and power amplification of the driving laser pulse in a strongly-driven laser wakefield accelerator. Simultaneous measurement of the transmitted pulse energy and temporal shape indicate an increase in peak power from $187 \pm 11$ TW to a maximum of $318 \pm 12$ TW after 13 mm of propagation in plasma density of $0.9 \times 10^{18}$ cm$^{-3}$. The power amplification is correlated with the injection and acceleration of electrons in the nonlinear wakefield. This process is modeled by including localized redshift and subsequent group delay dispersion at the laser pulse …
Plasma Wakefield Accelerators promise huge acceleration gradients that are three orders of magnitude greater than today's conventional radio frequency (RF) accelerators. These novel accelerators show also the potential of diminishing the size of the future accelerators nearly by the same factor. This review gives brief explanations and the working principles of the Plasma Wakefield Accelerators and shows the recent developments of the field. The current challenges are given and the potential future use of the Plasma Wakefield Accelerators are discussed.
A new electron injection scheme is proposed in sub-relativistic plasma wakefield accelerators. A transverse laser ionizes a dopant gas and ponderomotively accelerates the released electrons in the direction of wake propagation. This process enables electron trapping in the wakefield even for a wakefield potential below the trapping threshold. We study the scheme theoretically and by means of particle-in-cell simulations to demonstrate high-quality beam formation and acceleration with sub-micrometer normalized emittances and sub-percent uncorrelated energy spreads.
Betatron x-ray sources from laser-plasma accelerators combine compactness, high peak brightness, femtosecond pulse duration and broadband spectrum. However, when produced with Terawatt class lasers, their energy was so far restricted to a few kilo-electronvolt (keV), limiting the range of possible applications. Here we present a simple method to increase the energy and the flux by an order of magnitude without increasing the laser energy. The orbits of the relativistic electrons emitting the radiation were controlled using density tailored plasmas so that the efficiency of the Betatron source …
A controllable injection scheme is key to producing high quality laser-driven electron beams and X-rays. Self-injection is the most straightforward scheme leading to high current and peak energies, but is susceptible to variations in laser parameters and target characteristics. In this work improved control of electron self-injection in the nonlinear cavity regime using two laser-pulses propagating in tandem is investigated. In particular the advantages of the tandem-pulse scheme in terms of injection threshold, electron energy and beam properties in a regime relevant to betatron radiation are…
Accelerating particles to high energies with a high-gradient wakefield accelerator may require use of multiple stages. Coupling beams from one stage to another can be difficult due to high divergence and non-negligible energy spreads. We review the challenges, technical requirements and currently proposed methods for solving the staging problem.
We reconstruct spectra of secondary X-rays from a tunable 250-350 MeV laser wakefield electron accelerator from single-shot X-ray depth-energy measurements in a compact (7.5 $\times$ 7.5 $\times$ 15 cm), modular X-ray calorimeter made of alternating layers of absorbing materials and imaging plates. X-rays range from few-keV betatron to few-MeV inverse Compton to >100 MeV bremsstrahlung emission, and are characterized both individually and in mixtures. Geant4 simulations of energy deposition of single-energy X-rays in the stack generate an energy-vs-depth response matrix for a given stack confi…
The acceleration gradients generated in a laser- or beam-driven plasma wakefield accelerator are typically three orders of magnitude greater than those produced by a conventional accelerator, and hence plasma accelerators can open a route to a new generation of very compact machines. In addition, plasma-based accelerators can generate beams with unique properties, such as tens of kiloamp peak currents, attosecond bunch duration, ultrahigh brightness and intrinsic particle beam-laser pulse synchronization. In this roadmap we review the status of plasma accelerator research in the UK. We outline…
Multistage coupling of laser-wakefield accelerators is essential to overcome laser energy depletion for high-energy applications such as TeV level electron-positron colliders. Current staging schemes feed subsequent laser pulses into stages using plasma mirrors, while controlling electron beam focusing with plasma lenses. Here a more compact and efficient scheme is proposed to realize simultaneous coupling of the electron beam and the laser pulse into a second stage. A curved channel with transition segment is used to guide a fresh laser pulse into a subsequent straight channel, while allowing…
Plasma wakefield acceleration in the nonlinear blowout regime has been shown to provide high acceleration gradients and high energy transfer efficiency while maintaining great beam quality for electron acceleration. In contrast, research on positron acceleration in this regime is still in a preliminary stage. We find that an on-axis electron filament can be self-consistently formed and maintained by loading an intense positron beam at the back of the electron beam driven blowout cavity. Via an analytic model and fully nonlinear simulations, we show this coaxial electron filament not only can f…
We discovered a novel effect that can cause witness emittance growth in plasma wakefield accelerators. The effect appears in linear or moderately nonlinear plasma waves. The witness experiences a time-varying focusing force and loses quality during the time required for the drive beam to reach transverse equilibrium with the plasma wave. The higher the witness charge, the lower the emittance growth rate because of additional focusing of the witness by its own wakefield. However, the witness head always degrades, and the boundary between degraded and intact parts gradually propagates backward a…
The energy spread in laser-wakefield accelerators is primarily limited by the energy-chirp introduced during the injection and acceleration processes. Here we propose and demonstrate the use of longitudinal density tailoring to adapt the accelerating fields and reduce the chirp at the end of the accelerator. Experimental data supported by 3D PIC simulations show that broadband electron beams can be converted to quasi-monoenergetic beams of less than 10% energy spread while maintaining a high charge of more than 120 pC. In the linear and quasi-linear regimes of wakefield acceleration, the metho…
A new injection scheme using the interference of two coaxial laser pulses is proposed for generating high quality beams in laser wakefield accelerators. In this scheme, a relatively loosely focused laser pulse drives the plasma wakefield, and a tightly focused laser pulse with similar intensity triggers interference ring pattern which creates onion-like multi sheaths in the plasma wakefield. Due to the wavefront curvature change after the focal position of the tightly focused laser, the innermost sheath of the wakefield expands, which slows down the effective phase velocity of the wakefield an…
Bright dual-pulse betatron X-ray generation from a laser wakefield accelerator
Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Zhengzhou University（郑州大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；Tsinghua University（清华大学）
Single cycle laser pulse propagating inside a plasma causes controllable asymmetric plasma electron expulsion from laser according to laser carrier envelope phase (CEP) and forms an oscillating plasma bubble. Bubble's transverse wakefield is modified, exhibiting periodic modulation. Injection scheme for a laser wakefield accelerator combining a single cycle low frequency laser pulse and a many cycle high frequency laser pulse is proposed. The co-propagating laser pulses form a transversely oscillating wakefield which efficiently traps and accelerates electrons from background plasma. By tuning…
Non-invasive characterization of transverse beam emittance of electrons from a laser-plasma wakefield accelerator in the bubble regime using betatron x-ray radiation
我们提出并使用一种技术来测量激光尾流场加速的相对论电子束的横向发射度。该技术是基于由$v_{\perp}/v_{\parallel}$给出的电子束发散度、测量的纵向谱$γ_\parallel$和气泡$r_{\perp}$中的横向电子束团尺寸的同时测量。后者是通过测量气泡中加速电子束团发射的x射线的源尺寸获得的。我们测量了一个\textit{normalised} RMS束横向发射度$<0.5$ $π$ mm $\:$ mrad作为上限的空间高斯，光谱准单能电子束与230兆电子伏的能量在气泡制度与数值模拟和分析理论。
We present experimental results on a plasma wakefield accelerator (PWFA) driven by high-current electron beams from a laser wakefield accelerator (LWFA). In this staged setup stable and high quality (low divergence and low energy spread) electron beams are generated at an optically-generated hydrodynamic shock in the PWFA. The energy stability of the beams produced by that arrangement in the PWFA stage is comparable to both single-stage laser accelerators and plasma wakefield accelerators driven by conventional accelerators. Simulations support that the intrinsic insensitivity of PWFAs to driv…
Laser wakefield acceleration modeling using the Lorentz-boosted frame technique in the particle-in-cell code has demonstrated orders of magnitude speedups. A convergence study was previously conducted in cases with external injection in the linear regime and without injection in the nonlinear regime, and the obtained results have shown a convergence within the percentage level. In this article, a convergence study is carried out to model electron self-injection in the 2-1/2D configuration. It is observed that the Lorentz-boosted frame technique is capable of modeling complex particle dynamics …
Plasma-based accelerators have achieved tremendous progress in the past few decades, thanks to the advances of high power lasers and the availability of high-energy and relativistic particle beams. However, the electrons (or positrons) accelerated in the plasma wakefields are subject to radiation losses, which generally suppress the final energy gains of the beams. In this paper, radiation reaction in plasma-based high-energy accelerators is investigated using test particle approach. Energy-frontier TeV colliders based on a multiple stage laser-driven plasma wakefield accelerator and a single-…
Self-Adaptive Stabilization and Quality Boost for Electron Beams from All-Optical Plasma Wakefield Accelerators
University of Strathclyde（思克莱德大学）；Ludwig-Maximilians-Universität München（慕尼黑大学）；Heinrich Heine University Düsseldorf（杜塞尔多夫大学）；Cockcroft Institute（科克克罗夫特研究所）；Forschungszentrum Jülich（于利希研究中心）；École Polytechnique（巴黎综合理工学院）；Helmholtz-Zentrum Dresden–Rossendorf（德累斯顿罗森多夫亥姆霍兹中心）；Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）
