Hot spots and dark current in advanced plasma wakefield accelerators

Manahan, G. G.; Deng, Aihua; Karger, O.; Xi, Yunfeng; Knetsch, A.; Litos, M.; Wittig, G.; Heinemann, Thomas; Smith, Jonathan; Sheng, Z. M.; Jaroszynski, D. A.; Andonian, G.; Bruhwiler, D.; Rosenzweig, J.; Hidding, B.

doi:10.1103/physrevaccelbeams.19.011303

Cited by 17 publications

(24 citation statements)

References 35 publications

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“…We use an artificially short plasma wavelength to reduce the computational load, resulting in wakefield and driver field 'hot spots' of very high electric fields. This prohibits the use of H/He mixtures to realize the underdense photocathode PWFA because of He ionization at these hot spots, which impairs the laser-induced helium ionization and also leads to dark current 66 . Instead, we use a one-component version of the TH based on lithium, where Li is pre-ionized and the further ionization to Li + is exploited to generate the laser-released bunches.…”

Section: Methodsmentioning

confidence: 99%

Single-stage plasma-based correlated energy spread compensation for ultrahigh 6D brightness electron beams

et al. 2017

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Plasma photocathode wakefield acceleration combines energy gains of tens of GeV m−1 with generation of ultralow emittance electron bunches, and opens a path towards 5D-brightness orders of magnitude larger than state-of-the-art. This holds great promise for compact accelerator building blocks and advanced light sources. However, an intrinsic by-product of the enormous electric field gradients inherent to plasma accelerators is substantial correlated energy spread—an obstacle for key applications such as free-electron-lasers. Here we show that by releasing an additional tailored escort electron beam at a later phase of the acceleration, when the witness bunch is relativistically stable, the plasma wave can be locally overloaded without compromising the witness bunch normalized emittance. This reverses the effective accelerating gradient, and counter-rotates the accumulated negative longitudinal phase space chirp of the witness bunch. Thereby, the energy spread is reduced by an order of magnitude, thus enabling the production of ultrahigh 6D-brightness beams.

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Section: Methodsmentioning

confidence: 99%

Single-stage plasma-based correlated energy spread compensation for ultrahigh 6D brightness electron beams

et al. 2017

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“…1 and to excite a large amplitude plasma wave by expelling plasma electrons by means of its unipolar radial electric fields E r (r) = Q d /(2π) 3/2 ε 0 σ z r [1−exp(−r 2 /2σ r )] while keeping the heavy ions immobile. At the same time, the parameters are balanced towards dark-current-free PWFA operation such that the maximum radial electric field E r,max = 28 GV m −1 is below the tunnel-ionization threshold of the background helium gas of density n He = 1.5 × 10 17 cm −3 [34]. A moderate intensity laser pulse trailing the driver beam at the distance Δξ=115 μm with the normalized amplitude a 0 =0.018, FWHM pulse duration τ 0 =30 fs, and rms spot size w 0 =7 μm, reaches its focal position at z i =2 mm where the laser pulse intensity is just above the tunnel-ionization threshold of the neutral helium.…”

Section: Electron Beam Generation and Acceleration Pic Modellingmentioning

confidence: 99%

Plasma wakefield accelerator driven coherent spontaneous emission from an energy chirped electron pulse

et al. 2020

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Plasma accelerators (Esary et al 2009 Rev. Mod. Phys. 81 1229) are a potentially important source of high energy, low emittance electron beams with high peak currents generated within a relatively short distance. As such, they may have an important application in the driving of coherent light sources such as the Free Electron Laser (FEL) which operate into the x-ray region (McNeil and Thompson 2010 Nat. Photon. 4 814-21). While novel plasma photocathodes (Hidding et al 2012 Phys. Rev.Lett. 108 035001) may offer orders of magnitude improvement to the normalized emittance and brightness of electron beams compared to Radio Frequency-driven accelerators, a substantial challenge is the energy spread and chirp of beams, which can make FEL operation impossible. In this paper it is shown that such an energychirped, ultrahigh brightness electron beam, with dynamically evolving current profile due to ballistic bunching at moderate energies, can generate significant coherent radiation output via the process of Coherent Spontaneous Emission (CSE) (Campbell and McNeil 2012 Proc. FEL2012 (Nara, Japan)). While this CSE is seen to cause some FEL-induced electron bunching at the radiation wavelength, the dynamic evolution of the energy chirped pulse dampens out any high-gain FEL interaction. This work may offer the prospect of a future plasma driven FEL operating in the high-gain Self Amplified CSE mode.

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“…r k 3 p exceeds the blowout conditionQ > 1, where N d is the total number of electrons in the driver beam, σ z and σ r are the driver beam longitudinal and radial dimensions, respectively, and k p = 2π/λ p is the inverse plasma skin depth. At the same time, it is ensured that the PWFA-stage can be operated dark-current-free 16 by avoiding unwanted hot spots within the effective trapping volume. Once the blowout structure is formed, a co-propagating, low intensity plasma photocathode laser pulse releases electrons with negligible transverse momentum directly within the blowout structure.…”

Section: Generation Of Ultrahigh 6d Brightness Electron Beamsmentioning

confidence: 99%

“…At high plasma and large driver electron bunch densities, the electric fields around the drive beam as well as at the wakefield vertex are large. Only a small range of plasma densities permitted sufficiently large plasma cavities on the one hand, and avoidance of hot spots which would lead to driver beam or wakefield ionization of helium 16 on the other hand, or at least to suppress trapping of such hot spot-generated sources of dark current. Operation at longer plasma wavelengths reduces the wakefield strength and hence enables safely to prevent potential wake ionization of helium.…”

Section: E210: Experimental Demonstration Of Plasma Phothocathode Pwfmentioning

confidence: 99%

Plasma accelerator-based ultrabright x-ray beams from ultrabright electron beams

Habib

Scherkl

Manahan

et al. 2019

Advances in Laboratory-Based X-Ray Sources, Optics, and Applications VII

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We provide a pathway to compact ultrabright light sources, based on ultrabright, high energy electron beams emerging from a combination of plasma wakefield acceleration and plasma photocathodes. While plasma acceleration is known to produce accelerating fields three or four orders of magnitude larger than conventional accelerators, the plasma photocathode allows production of electron beams three or four orders of magnitude brighter than conventional, and thus is suitable to unleash the full potential of plasma accelerators. In particular, this is the case for various types of light sources, which profit enormously from an increased electron beam brightness. Building on the recent first experimental demonstration of the plasma photocathode, in this work we discuss the prospects of plasma photocathodes for key photon source approaches such as x-ray free-electron lasers, betatron radiation, ion-channel lasers and inverse Compton scattering.

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Hot spots and dark current in advanced plasma wakefield accelerators

Cited by 17 publications

References 35 publications

Single-stage plasma-based correlated energy spread compensation for ultrahigh 6D brightness electron beams

Single-stage plasma-based correlated energy spread compensation for ultrahigh 6D brightness electron beams

Plasma wakefield accelerator driven coherent spontaneous emission from an energy chirped electron pulse

Plasma accelerator-based ultrabright x-ray beams from ultrabright electron beams

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