Observation of Electron Energies Beyond the Linear Dephasing Limit from a Laser-Excited Relativistic Plasma Wave

Gordon, Daniel; Tzeng, K. C.; Clayton, C. E.; Dangor, A. E.; Malka, Victor; Marsh, K. A.; Modena, A.; Mori, W. B.; Muggli, P.; Najmudin, Z.; Neely, D.; Danson, C.; Joshi, C.

doi:10.1103/physrevlett.80.2133

Cited by 210 publications

(107 citation statements)

References 24 publications

(19 reference statements)

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“…However, experiments with gas jet targets consistently produce a fast electron spectrum with a considerably higher effective temperature, from a few MeV to over 10 MeV. 9,[15][16][17][18][19]33,34 Moreover, it was experimentally found that about 5% of the laser energy appears in the form of a beam of collimated relativistic electrons. 9 It is apparent that an acceleration mechanism due to collective effects is responsible for this rather efficient laser energy transfer to plasma electrons.…”

Section: Discussionmentioning

confidence: 99%

“…9 and 10. Even though the generation of relativistic electrons with short laser pulses in gas-jet targets has been reported in a number of similar investigations, [15][16][17][18] to our knowledge this is the first experiment in which an 1-TW table-top laser system operating at 10 Hz was utilized for that purpose. Recently, similar measurements were reported using the same type of laser but at higher intensities.…”

Section: Introductionmentioning

confidence: 99%

“…The last factor is referred to as ''dephasing limit'' and it corresponds to the case where the electron has acquired so much energy that it moves ahead of the accelerating flank of the potential well and starts de-accelerating. 17 The maximum electron energy gain through this process has been shown to be ␥ max ϭ2 2 / p 2 , 35 which indicates that lower plasma densities favor high energy gain, but this presumes long acceleration lengths which is difficult to produce in practice. In the high density regime in which the laser pulse duration encompasses several plasma periods, i.e., L Ͼ2/ p , the laser envelope undergoes an instability and becomes ''selfmodulated'' at the plasma period.…”

Section: B Electron Accelerationmentioning

confidence: 99%

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Generation of MeV electrons and positrons with femtosecond pulses from a table-top laser system

Gahn¹,

Tsakiris²,

Pretzler³

et al. 2002

Physics of Plasmas

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In experiments, the feasibility was demonstrated of generating multi-MeV electrons in a form of a collimated beam utilizing a table-top laser system delivering 200 fs pulses with P L ϭ1.2 TW and 10 Hz capability. The method uses the process of relativistic self-channeling in a high-density gas jet producing electron densities in the range of 3ϫ1019 -6ϫ10 20 cm Ϫ3 . In a thorough investigation, angularly resolved and absolutely calibrated electron spectra were measured and their dependence on the plasma density, laser intensity, and gas medium was studied. For the optimum electron density of n e ϭ2ϫ10 20 cm Ϫ3 the effective temperature of the electron energy distribution and the channel length exhibit a maximum of 5 MeV and 400 m respectively. The laser-energyto-MeV-electron efficiency is estimated to be 5%. In a second step, utilizing the multi-MeV electron beam anti-particles, namely positrons, were successfully generated in a 2 mm Pb converter. The average intensity of this new source of positrons is estimated to be equivalent to a radioactivity of 2ϫ10 8 Bq and it exhibits a very favorable scaling for higher laser intensities.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: B Electron Accelerationmentioning

confidence: 99%

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Generation of MeV electrons and positrons with femtosecond pulses from a table-top laser system

Gahn¹,

Tsakiris²,

Pretzler³

et al. 2002

Physics of Plasmas

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“…In linear plasma theory [14] the wakefield amplitude increases as N= 2 z , provided the plasma density is increased such that k p z 2 p where N is the number of electrons in the bunch, z is the bunch length, and k p ! p =c is the inverse of the plasma collisionless skin depth.…”

mentioning

confidence: 99%

Multi-GeV Energy Gain in a Plasma-Wakefield Accelerator

et al. 2005

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3module. A 28.5 GeV electron beam with 1:8 10 10 electrons is compressed to 20 m longitudinally and focused to a transverse spot size of 10 m at the entrance of a 10 cm long column of lithium vapor with density 2:8 10 17 atoms=cm 3 . The electron bunch fully ionizes the lithium vapor to create a plasma and then expels the plasma electrons. These electrons return one-half plasma period later driving a large amplitude plasma wake that in turn accelerates particles in the back of the bunch by more than 2.7 GeV.Plasmas have extraordinary potential for advancing the energy frontier in high-energy physics due to the large focusing and accelerating fields that are generated.Beam-plasma interactions have demonstrated focusing gradients of MT=m [1] while laser plasma interactions have demonstrated GeV=cm accelerating gradients [2 -7] over distances of a few mm. Beam-driven plasmawakefield accelerators (PWFA) have recently demonstrated acceleration and focusing of both electrons [8,9] and positrons [10,11] in meter scale plasmas.The experiment described in this Letter uses an ultrarelativistic electron bunch to simultaneously create a plasma in lithium vapor and drive a large amplitude plasma wave. When the electron bunch enters the lithium vapor, the electric field of the leading portion of the bunch ionizes the valence electron of each lithium atom in its vicinity leaving fully ionized neutral plasma for the remainder of the bunch [12,13]. The plasma electrons are then expelled from the beam volume and return one-half plasma period later. The returning plasma electrons form density concentrations on axis behind the bunch leading to a large accelerating field for the particles in the back of the bunch.In linear plasma theory [14] the wakefield amplitude increases as N= 2 z , provided the plasma density is increased such that k p z 2 p where N is the number of electrons in the bunch, z is the bunch length, and k p ! p =c is the inverse of the plasma collisionless skin depth. The nonlinear or blowout regime is reached when the electron bunch density n b N= 2 3=2 z 2 r is greater than the plasma density n p and the beam radius satisfies r c=! p . In the blowout regime, for bunch lengths on the order of the plasma wavelength, the plasma electrons are expelled from the beam volume to a radius r c 2 N= 2 3=2 z n p q leaving behind a pure ion column. This experiment is in a regime in which the electron bunch radius, bunch length, ion channel radius, and plasma wavelength are all on the same order. Although the experiments described here are on the edge of the blowout regime, numerical simulations indicate the N= 2 z increase in plasma-wakefield amplitude can still be realized [15]. Verification of the dramatic increase in accelerating gradient predicted for short bunches is a critical milestone for the application of plasma-wakefield accelerators to future high-energy accelerators and colliders.A single 28.5 GeV bunch of 1:8 10 10 electrons from the Stanford Linear Accelerator Center (SLAC) linac enters the Final Focus Test B...

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“…This operational regime is called the self modulated laser wakefield acceleration (SM-LWFA). Although experiments with such high energy, high power, sub-picosecond Nd:glass based lasers (for example, 250 TW in 650 fs [27], τ L τ p ) are still actively being pursued [27][28][29][30][31][32][33][34][35][36][37][38][39], the majority of research has shifted to experiments with shorter pulse duration (τ P τ L 100 fs), higher repetition rate Ti:Sapphire based CPA laser systems [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. Experimental setups for SM-LWFA experiments were simple and similar everywhere.…”

Section: Plasma Based Accelerator Experimentsmentioning

confidence: 99%

Control of Laser Plasma Based Accelerators up to 1 GeV

Nakamura

2007

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This dissertation documents the development of a broadband electron spectrometer (ESM) for GeV class Laser Wakefield Accelerators (LWFA), the production of high quality GeV electron beams (e-beams) for the first time in a LWFA by using a capillary discharge guide (CDG), and a statistical analysis of CDG-LWFAs.An ESM specialized for CDG-LWFAs with an unprecedentedly wide momentum acceptance, from 0.01 to 1.1 GeV in a single shot, has been developed. Simultaneous measurement of e-beam spectra and output laser properties as well as a large angular acceptance (> ±10 mrad) were realized by employing a slitless scheme. A scintillating screen (LANEX Fast back ,LANEX-FB) -camera system allowed faster than 1 Hz operation and evaluation of the spatial properties of e-beams. The design provided sufficient resolution for the whole range of the ESM (below 5% for beams with 2 mrad divergence).The calibration between light yield from LANEX-FB and total charge, and a study on the electron energy dependence (0.071 to 1.23 GeV) of LANEX-FB were performed at the Advanced light source (ALS), Lawrence Berkeley National Laboratory (LBNL). Using this calibration data, the developed ESM provided a charge measurement as well.The production of high quality electron beams up to 1 GeV from a centimeter-scale ii accelerator was demonstrated. The experiment used a 310 µm diameter gas-filled capillary discharge waveguide that channeled relativistically-intense laser pulses (42 TW, A statistical analysis of the CDG-LWFAs' performance was carried out. By taking advantage of the high repetition rate experimental system, several thousands of shots were taken in a broad range of the laser and plasma parameters. An analysis program was developed to sort and select the data by specified parameters, and then to evaluate performance statistically.The analysis suggested that the generation of GeV-level beams comes from a highly unstable and regime. By having the plasma density slightly above the threshold density for self injection, 1) the longest dephasing length possible was provided, which led to the generation of high energy e-beams, and 2) the number of electrons injected into the wakefield was kept small, which led to the generation of high quality (low energy spread) e-beams by minimizing the beam loading effect on the wake. The analysis of the stable half-GeV beam regime showed the requirements for stable self injection and acceleration. A small change of discharge delay t dsc , and input energy E in , significantly affected performance.The statistical analysis provided information for future optimization, and suggested possible schemes for improvment of the stability and higher quality beam generation. A CDG-LWFA is envisioned as a construction block for the next generation accelerator, enabling significant cost and size reductions.

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Observation of Electron Energies Beyond the Linear Dephasing Limit from a Laser-Excited Relativistic Plasma Wave

Cited by 210 publications

References 24 publications

Generation of MeV electrons and positrons with femtosecond pulses from a table-top laser system

Generation of MeV electrons and positrons with femtosecond pulses from a table-top laser system

Multi-GeV Energy Gain in a Plasma-Wakefield Accelerator

Control of Laser Plasma Based Accelerators up to 1 GeV

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