Parameter study of acceleration of externally injected electrons in the linear laser wakefield regime

Dijk, van W Walter; Geer, van der Sb Bas; Wiel, van der Mj Marnix; Brussaard, Gjh Seth

doi:10.1063/1.2977765

Cited by 5 publications

(9 citation statements)

References 34 publications

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“…The matched spot size for laser guiding in such a plasma is around 20-50 lm (Refs. [22][23][24][25], in the same range as the measured focal spot, so that it can be expected that a reasonable fraction of the electron bunch can be captured and accelerated in LWA (a detailed simulation using all measured parameters will be presented in Sec. IV).…”

Section: Focus Spot and Focus Stabilitymentioning

confidence: 99%

“…36 To keep the calculation time acceptable, the wakefield potential and laser pulse envelope are assumed to be time-independent in the frame of the laser pulse (quasi-stationary solution), similar to the approach of Van Dijk. 25,26,31 The properties of the injected electron bunches that are used as input parameters by GPT were those of the measurements described in Sec. III.…”

Section: Simulations Of Lwa With External Injection Of the Measurmentioning

confidence: 99%

“…An added advantage of using an external source for the injection of electrons is that acceleration becomes possible not only in nonlinear wakefields, in which all experiments above are performed, [21][22][23] but also in the linear regime with modest sub-10 TW lasers and a high repetition rate. 21,[24][25][26] In the linear regime, the electron bunch is injected shortly behind the laser pulse so it can occupy the first troughs, or 'buckets', of the plasma wave. It was believed that the injected bunch had to be shorter than the plasma wavelength (under 50 lm) with a synchronization between electron bunch and the plasma wave driving laser pulse even shorter than the plasma wavelength (sub 10 fs) in order to obtain accelerated electron bunches with low energy spread.…”

Section: Introductionmentioning

confidence: 99%

“…It has been shown that in case of an injected bunch which exceeds the plasma wavelength, the wakefield will act as a chopper and transform the injected bunch in a train of accelerated sub-bunches. 25,27 Because only the accelerating and focusing phase is suitable for acceleration, a maximum of $10% of the initially injected charge can be accelerated. The trapping conditions are determined by the combination of wakefield amplitude and the injected electron energy.…”

Section: Introductionmentioning

confidence: 99%

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Experimental validation of a radio frequency photogun as external electron injector for a laser wakefield accelerator

Stragier

Luiten

Geer

et al. 2011

Journal of Applied Physics

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A purpose-built RF-photogun as external electron injector for a laser wakefield accelerator has been thoroughly tested. Different properties of the RF-photogun have been measured such as energy, energy spread and transverse emittance. The focus of this study is the investigation of the smallest possible focus spot and focus stability at the entrance of the plasma channel. For an electron bunch with 10 pC charge and 3.7 MeV kinetic energy, the energy spread was 0.5% with a shot-to-shot stability of 0.05%. After focusing the bunch by a pulsed solenoid lens at 140 mm from the middle of the lens, the focal spot was 40 μm with a shot-to-shot stability of 5 μm. Higher charge leads to higher energy spread and to a larger spot size, due to space charge effects. All properties were found to be close to design values. Given the limited energy of 3.7 MeV, the properties are sufficient for this gun to serve as injector for one particular version of laser wakefield acceleration, i.e., injection ahead of the laser pulse. These measured electron bunch properties were then used as input parameters for simulations of electron bunch injection in a laser wakefield accelerator. The arrival time jitter was deduced from measurements of the energy fluctuation, in combination with earlier measurements using THz coherent transition radiation, and is around 150 fs in the present setup. The bunch length in the focus, simulated using particle tracking, depends on the accelerated charge and goes from 100 fs at 0.1 pC to 1 ps at 50 pC. When simulating the injection of the 3.7 MeV electron bunch of 10 pC in front of a 25 TW laser pulse with a waist of 30 μm in a plasma with a density of 0.7 × 1024 m−3, the maximum accelerated charge was found to be 1.2 pC with a kinetic energy of ∼900 MeV and an energy spread of ∼5%. The experiments combined with the simulations show the feasibility of external injection and give a prediction of the output parameters that can be expected from a laser wakefield accelerator with external injection of electrons.

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Section: Focus Spot and Focus Stabilitymentioning

confidence: 99%

Section: Simulations Of Lwa With External Injection Of the Measurmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Experimental validation of a radio frequency photogun as external electron injector for a laser wakefield accelerator

Stragier

Luiten

Geer

et al. 2011

Journal of Applied Physics

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“…Behind the laser pulse (a = 0) this can be written as 72) where the last term is an approximation for small Φ, which occurs at small drive intensities (a ≪ 1). This approximation yields a sinusoidally perturbed plasma wave with wavelength λ p = 2π/k p .…”

Section: D Laser Wakefield In the Relativistic Casementioning

confidence: 99%

Theoretical investigation of external injection schemes for laser wakefield acceleration

Luttikhof¹

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Effects of timing and stability on laser wakefield acceleration using external injection

Dijk

Corstens

Geer

et al. 2009

Phys. Rev. ST Accel. Beams

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The effects of experimental variations in the synchronization, laser power, and plasma density on the final beam parameters of externally injected electrons accelerated in a plasma wave are studied using a hybrid model. This model combines a relativistic fluid description of the plasma wave generated by the laser pulse with particle tracking of the accelerated electrons. For cases in which the effects of beam loading and laser depletion can be neglected, the two parts can be separated, allowing a significant reduction in computational power needed compared to particle in cell codes. Two different approaches to externally injecting electrons into plasma waves are studied: In the first case, the electrons are injected behind a laser pulse with a 0 ¼ 0:32. In the second case, electrons are injected in front of the laser pulse in three different laser regimes a 0 ¼ 0:32, a 0 ¼ 0:56, and a 0 ¼ 1:02, ranging from linear to nonlinear. For these four cases, the effects of expected experimental variations in synchronization (AE 500 fs), laser power (AE 10%), and plasma density (AE 30%) are studied. From these simulations, it becomes clear that in some cases, even a small variation in one of these parameters can create a large change in the final energy, energy spread, and trapped charge. For lower laser intensities, the method of injecting behind the laser pulse is the least sensitive to fluctuations while injection in front of the laser pulse becomes less sensitive at higher intensities.

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Parameter study of acceleration of externally injected electrons in the linear laser wakefield regime

Cited by 5 publications

References 34 publications

Experimental validation of a radio frequency photogun as external electron injector for a laser wakefield accelerator

Experimental validation of a radio frequency photogun as external electron injector for a laser wakefield accelerator

Theoretical investigation of external injection schemes for laser wakefield acceleration

Effects of timing and stability on laser wakefield acceleration using external injection

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