A focal-spot diagnostic for on-shot characterization of high-energy petawatt lasers

Bromage, J.; Bahk, S.-W.; Irwin, David; Kwiatkowski, J.; Pruyne, A.; Millecchia, M.; Moore, Michael D.; Zuegel, J. D.

doi:10.1364/oe.16.016561

Cited by 38 publications

(20 citation statements)

References 12 publications

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“…32 The central wavelength of the pulse is k ¼ 1.053 lm and the beam was linearly polarized. The beam was focused with an f=2 off-axis parabola to a focal spot which was characterized on every shot via phaseretrieval-assisted wavefront measurements 33 to produce a fluence map. These fluence maps are used to calculate the peak vacuum intensity and peak normalized vector potential, a 0 , for each shot.…”

Section: Methodsmentioning

confidence: 99%

High-power, kilojoule laser interactions with near-critical density plasma

et al. 2011

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Experiments were performed using the Omega EP laser, which provided pulses containing 1kJ of energy in 9ps and was used to investigate high-power, relativistic intensity laser interactions with near-critical density plasmas, created from foam targets with densities of 3-100 mg=cm 3. The effect of changing the plasma density on both the laser light transmitted through the targets and the proton beam accelerated from the interaction was investigated. Two-dimensional particle-in-cell simulations enabled the interaction dynamics and laser propagation to be studied in detail. The effect of the laser polarization and intensity in the two-dimensional simulations on the channel formation and electron heating are discussed. In this regime, where the plasma density is above the critical density, but below the relativistic critical density, the channel formation speed and therefore length are inversely proportional to the plasma density, which is faster than the hole boring model prediction. A general model is developed to describe the channel length in this regime. V

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Section: Methodsmentioning

confidence: 99%

High-power, kilojoule laser interactions with near-critical density plasma

et al. 2011

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“…A high-resolution wavefront sensor measured the on-shot fluence distribution in the focal plane of the OMEGA EP pulse at full energy. 22 More than 30% of the laser energy had an intensity >1 Â 10 19 W/cm 2 , while the average intensity within R 80 was (6 6 2) Â 10 18 W/cm 2 . The focal pattern and R 80 varied slightly from shot to shot.…”

Section: Targets and Laser Setupmentioning

confidence: 95%

Initial cone-in-shell fast-ignition experiments on OMEGA

et al. 2011

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“…If a Gaussian temporal profile is assumed, the peak vacuum intensities for typical shots are 3.7 × 10 19 W cm −2 for the 8 ps pulse and 2 × 10 19 I 1.5 × 10 20 W cm −2 for the 1 ps pulse (due to a range of laser pulse energies), corresponding to peak normalized vector potentials 4 a 0 11. On-target intensity maps have been reconstructed using on-shot wavefront data [22].…”

Section: Experimental Set-upmentioning

confidence: 99%

Surface waves and electron acceleration from high-power, kilojoule-class laser interactions with underdense plasma

et al. 2013

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Experiments were performed on the Omega EP laser facility to study laser pulse propagation, channeling phenomena and electron acceleration from high-intensity, high-power laser interactions with underdense plasma. A CH plasma plume was used as the underdense target and the interaction of the laser pulse channeling through the plasma was imaged using proton radiography. High-energy electron spectra were measured for different experimental laser parameters. Structures observed along the channel walls are interpreted as having developed from surface waves, which are likely to serve as an injection mechanism of electrons into the cavitated channel for acceleration via direct laser acceleration mechanisms. Two-dimensional particle-in-cell simulations give good agreement with these channeling and electron acceleration phenomena. IntroductionLaser-based plasma accelerators have become a highly promising alternative to conventional accelerators in recent years. Wakefield acceleration can be driven by a laser pulse or particle beam propagating through an underdense plasma, which produces a plasma wave with a phase velocity close to the speed of light, and can transfer energy to 'surfing' electrons trapped in the waves [1][2][3]. With the reduction of the laser pulse duration, a regime where the laser pulse duration matched the plasma frequency was achieved and this allowed significant advances in controlling and producing narrow energy spread electron beams [4][5][6]. Furthermore, transverse oscillations of the high-energy electron beams within the plasma wave structure leads to a very bright, directional x-ray source [7]. Using laser pulses of longer pulse duration produce a more complicated interaction, with the leading edge of the pulse producing plasma waves. However, if the laser pulse is intense enough, the ponderomotive force of the laser pulse expels the electrons from the regions of highest intensity to form a cavitated channel. Once the channel has formed, plasma waves are no longer present, but electrons are able to gain energy through direct laser acceleration (DLA) mechanisms [8,9].The study of this channel formation, the energy exchange from the laser pulse to electrons and the subsequent transport and dissipation of the energy is of specific relevance to the hole boring fast ignition inertial confinement fusion scheme [10]. A high-intensity laser pulse is used to form a channel though the low-density coronal plasma of the compressed fuel, so that a second laser pulse can be guided to the dense fuel and strongly heat the electrons in this region to ignite the system. The aim of this study is to gain a better understanding of the energy transfer and electron heating mechanisms in such systems.Several DLA mechanisms have been identified using particle-in-cell (PIC) simulations to accelerate electrons to energies exceeding the ponderomotive potential. The transfer of laser energy to the electrons can occur either through a stochastic acceleration mechanism [11,12], or via the coupling of quasi-static electric o...

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A focal-spot diagnostic for on-shot characterization of high-energy petawatt lasers

Cited by 38 publications

References 12 publications

High-power, kilojoule laser interactions with near-critical density plasma

High-power, kilojoule laser interactions with near-critical density plasma

Initial cone-in-shell fast-ignition experiments on OMEGA

Surface waves and electron acceleration from high-power, kilojoule-class laser interactions with underdense plasma

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