I. A. Egorova, A. V. Filatov, A. V. Prozorkevich, S. A. Smolyansky, D. B. Blaschke, M. Chubaryan
备注：
4 pages, 4 figures, Talk at the Helmholtz International Summer School "Dense Matter in heavy Ion Collisions and Astrophysics", August 21 - September 1, 2006, JINR Dubna, Russia; v2, misprints corrected
We consider methods of charged particle acceleration by means of high-intensity lasers. As an application we discuss a laser booster for heavy ion beams provided, e.g. by the Dubna nuclotron. Simple estimates show that a cascade of crossed laser beams would be necessary to provide additional acceleration to gold ions of the order of GeV/nucleon.
We report with single particle simulations that longitudinal chromatism, a commonly occuring spatio-temporal coupling in ultrashort laser pulses, can have a significant influence in the longitudinal acceleration of electrons via high-power, tightly-focused radially polarized laser beams. This effect can be advantageous, and even more-so when combined with small values of temporal chirp. However, the effect can also be highly destructive when the magnitude and sign of the longitudinal chromatism is not ideal, even at very small magnitudes. This motivates the characterization and understanding o…
A strongly mismatched regime of self-guided nonlinear laser-plasma acceleration in the bubble regime is modeled for optimization of Laser to Particle energy efficiency with application to recently proposed laser positron accelerator. The strong mismatch, in contrast with the matched condition, arises from the incident laser spot-size being much larger than that needed for equilibration of the laser ponderomotive and electron-ion charge-separation force in the plasma bubble. This is shown to be favorable for optimization of large self-injected electron charge and ultra-low transverse emittance.…
We present methods and preliminary observations of two pulse Direct Laser Acceleration in a Laser-Driven Plasma Accelerator. This acceleration mechanism uses a second co-propagating laser pulse to overlap and further accelerate electrons in a wakefield bubble, increasing energy at the cost of emittance when compared to traditional laser wakefield acceleration (LWFA). To this end, we introduce a method of femtosecond scale control of time delay between two co-propagating pulses. We show energy enhancement when the separation between the two pulses approaches the bubble radius.
We demonstrate that laser reflection acts as a catalyst for superponderomotive electron production in the preplasma formed by relativistic multipicosecond lasers incident on solid density targets. In 1D particle-in-cell simulations, high energy electron production proceeds via two stages of direct laser acceleration, an initial stochastic backward stage, and a final non-stochastic forward stage. The initial stochastic stage, driven by the reflected laser pulse, provides the pre-acceleration needed to enable the final stage to be non-stochastic. Energy gain in the electrostatic potential, which…
We discuss recent developments and challenges of beam dynamics in Dielectric Laser Acceleration (DLA), for both high and low energy electron beams. Starting from ultra-low emittance nanotip sources the paper follows the beam path of a tentative DLA light source concept. Acceleration in conjuction with focusing is discussed in the framework of Alternating Phase Focusing (APF) and spatial harmonic ponderomotive focusing. The paper concludes with an outlook to the beam dynamics in laser driven nanophotonic undulators, based on tilted DLA grating structures.
Dynamics of self-injected electron bunches has been numerically simulated in blowout regime at self-consistent change of electron bunch acceleration by plasma wakefield, excited by a laser pulse, to additional their acceleration by wakefield, excited by self-injected bunch. Advantages of acceleration by pulse train and bunch self-cleaning have been considered.
We report results on all-optical Thomson scattering intercepting the acceleration process in a laser wakefield accelerator. We show that the pulse collision position can be detected using transverse shadowgraphy which also facilitates alignment. As the electron beam energy is evolving inside the accelerator, the emitted spectrum changes with the scattering position. Such a configuration could be employed as accelerator diagnostic as well as reliable setup to generate x-rays with tunable energy.
An overview of research on laser-plasma based acceleration of ions is given. The experimental state of the art is summarized and recent progress is discussed. The basic acceleration processes are briefly reviewed with an outlook on hybrid mechanisms and novel concepts. Finally, we put focus on the development of engineered targets for enhanced acceleration and of all-optical methods for beam post-acceleration and control.
Comparative Analysis of Simulation Results of Dielectric Laser Acceleration of Non-relativistic Electrons in Transparent and Reflective Periodic Structures
Over the last decades, significant advances in high-power laser systems have enabled rapid progress in the development of laser-driven plasma accelerators. Today, the results obtained in beam stability and reproducibility present laser plasma acceleration as a viable and promising alternative to conventional accelerators. As several electron beam and secondary sources applications require high average currents, a major focus is now on increasing the beam's repetition rate. In the following, we introduce a novel plasma source for kHz electron acceleration, providing a continuous and spatially c…
Intense lasers can accelerate electrons to very high energy over a short distance. Such compact accelerators have several potential applications including fast ignition, high energy physics, and radiography. Among the various schemes of laser-based electron acceleration, vacuum laser acceleration has the merits of super-high acceleration gradient and great simplicity. Yet its realization has been difficult because injecting free electrons into the fast-oscillating laser field is not trivial. Here we demonstrate free-electron injection and subsequent vacuum laser acceleration of electrons up to…
We propose a hybrid laser-driven ion acceleration scheme using a combination target of a solid foil and a density-tailored background plasma. In the first stage, a sub-relativistic proton beam can be generated by the radiation pressure acceleration in the intense laser interaction with the solid foil. In the second stage, this sub-relativistic proton beam is further accelerated by the laser wakefield driven by the same laser pulse in a near-critical-density background plasma with a decreasing density profile. The propagating velocity of the laser front and the phase velocity of the excited wak…
The multi-stage technique for laser driven acceleration of electrons become a critical part of full-optical, jitter-free accelerators. Use of several independent laser drivers and shorter length plasma targets allows the stable and reproducible acceleration of electron bunches (or beam) in the GeV energies with lower energy spreads. At the same time the charge coupling, necessary for efficient acceleration in the consecutive acceleration stage(s), depends collectively on the parameters of the injected electron beam, the booster stage, and the non-linear transverse dynamics of the electron beam…
Staging laser wake-field acceleration is considered as a necessary technique for developing full-optical jitter-free electron accelerators. Splitting of the acceleration length into several technical parts with their lengths smaller than the dephasing length and with independent laser drivers allows generation of stable, reproducible acceleration fields. Temporal and spatial coupling of pre-accelerated electron bunches for their injection in the acceleration phase of a successive laser pulse wake field is the key part of the staging laser-driven acceleration. Here, characterization of the coup…
Dielectric laser accelerators (DLAs) use the nearfields created when a laser pulse impinges on a dielectric structure to accelerate charged particles. We provide an overview of the theory of operation of photon driven accelerators, from photons interacting with charged particles in a vacuum, to the advantages gained by introducing dielectric structures, with a discussion of their advantages and limitations. Furthermore we show the state of the art of the current development of dielectric laser accelerators, including acceleration, focusing, deflection, beam position monitoring, and advanced to…
Magnetic Vortex Acceleration (MVA) from near critical density targets is one of the promising schemes of laser-driven ion acceleration. 3D particle-in-cell simulations are used to explore a more extensive laser-target parameter space than previously reported on in the literature as well as to study the laser pulse coupling to the target, the structure of the fields, and the properties of the accelerated ion beam in the MVA scheme. The efficiency of acceleration depends on the coupling of the laser energy to the self-generated channel in the target. The accelerated proton beams demonstrate high…
The notions of acceleration gradient and deflection gradient are generalized to phasor quantities (complex-valued functions) in the context of dielectric laser acceleration (DLA). It is shown that the electromagnetic forces imparted on a near-resonant particle traversing a unit cell of a grating-type DLA can be conveniently described by generalized acceleration and deflection gradients. A~simple formulation of the Panofsky-Wenzel theorem in terms of the generalized gradients is given. It is shown that all particle transfer properties of a DLA unit cell can be derived from a single, complex-val…
A high-intensity laser beam propagating through a dense plasma drives a strong current that robustly sustains a strong quasi-static Mega Tesla-level azimuthal magnetic field. The transverse laser field efficiently accelerates electrons in the presence of such a field that confines the transverse motion and deflects the electrons in the forward direction, establishing the novel forward-sliding swing acceleration mechanism. Its advantage is a threshold rather than resonant behavior, accelerating electrons to high energies for sufficiently strong laser-driven currents. We study the electrons' dyn…
Backward-Propagating MeV Electrons in Ultra-Intense Laser Interactions: Standing Wave Acceleration and Coupling to the Reflected Laser Pulse
在空军研究实验室的一项实验中，由聚焦在连续水射流上的强（$\sim10^{18}$ W/cm $^2$）、$\sim$ 40 fs激光脉冲的{ \it反射}以kHz重复率产生激光加速电子束。本文采用粒子模拟方法研究了激光-靶相互作用过程中电子加速的物理机制。我们发现由入射和反射激光的重叠产生的驻波图案是特别重要的，因为这种驻波可以将电子“注入”到反射激光脉冲中，在那里电子被进一步加速。我们确定了两个制度的驻波加速：一个高度相对论的情况下（$a_0~\geq~1$），和一个适度的相对论的情况下（$a_0~\sim~0.5$），其操作在一个较大的分数的激光周期。在以前的研究中，其他小组已经研究了高度相对论性的情况，因为它在向前发射电子方面很有用。我们通过调查电子加速在{ \it镜面（背反射）方向}和在很宽的范围内的强度（$10^{17}-10^{19}$ W cm $^{-2}$）。
We propose a setup for positron acceleration consisting of an electron driver and a laser pulse creating a two-fold plasma column structure. The resulting wakefield is capable of accelerating positron bunches over long distances even when evolution of the driver is considered. The scheme is studied by means of particle-in-cell simulations. Further, the analytical expression for the accelerating and focusing fields are obtained, showing the equilibrium lines along which the witness bunch is accelerated.
An analytical optimization of plasma density profiles for downramp injection in laser wake-field acceleration
Università di Napoli “Federico II”（那不勒斯费德里科二世大学）；INFN, Sez. di Napoli（意大利国家核物理研究所那不勒斯分部）；Extreme Light Infrastructure - Nuclear Physics, IFIN-HH（极亮基础设施-核物理，IFIN-HH）
In the design of laser plasma electron injectors for multi-stage laser driven wakefield accelerators, the control of plasma density is a key element to stabilize the acceleration process. A cell with variable parameters is used to confine the gas and tailor the density profile. The gas filling process was characterized both experimentally and by fluid simulations. Results show a good agreement between experiments and simulations. Simulations were also used to study the effect of each of the gas cell parameters on the density distribution and show the possibility to finely control the density p…
The recent experimental data of anomalous magnetic moments strongly indicate the existence of new physics beyond the standard model. An energetic $μ^+$ beam is a potential option to the expected neutrino factories, the future muon colliders and the $μ$SR(the spin rotation, resonance and relaxation) technology. It is proposed a prompt acceleration scheme of the $μ^+$ beam in a donut wakefield driven by a shaped Laguerre-Gaussian (LG) laser pulse. The forward part of the donut wakefield can accelerate and also focus positive particle beams effectively. The LG laser is shaped by a near-critical-d…
The scaling laws for laser wakefield acceleration in the nonlinear, self-guided regime [Lu et al. Phys. Rev. Spec. Top. Accel. Beams 10, 061301 (2007)] are examined in detail using the quasi-3D version of the particle-in-cell code OSIRIS. We find that the scaling laws continue to work well as the plasma density is reduced while the normalized laser amplitude is kept fixed. For fixed laser energy, the energy gain of an isolated bunch of electrons can be improved with some loss in the bunch charge by shortening the normalized pulse length until self-guiding no longer occurs, and through the use …
