ABSTRACT Enhancement of X-ray production probability in a plasma-waveguide-based laser wakefield accelerator by insertion of a drift space is achieved. Dependencies of X-ray production probability on drift space parameters are consistent...
moreABSTRACT Enhancement of X-ray production probability in a plasma-waveguide-based laser wakefield accelerator by insertion of a drift space is achieved. Dependencies of X-ray production probability on drift space parameters are consistent with the drift-space model.
ABSTRACT Ionization injection triggered by short wavelength laser pulses inside a nonlinear wakefield driven by a longer wavelength laser is examined via multi-dimensional particle-in-cell simulations. We find that very bright electron...
moreABSTRACT Ionization injection triggered by short wavelength laser pulses inside a nonlinear wakefield driven by a longer wavelength laser is examined via multi-dimensional particle-in-cell simulations. We find that very bright electron beams can be generated through this two-color scheme in either collinear propagating or transverse colliding geometry. For a fixed laser intensity $I$, lasers with longer/shorter wavelength $\lambda$ have larger/smaller ponderomotive potential ($\propto I \lambda^2$). The two color scheme utilizes this property to separate the injection process from the wakefield excitation process. Very strong wakes can be generated at relatively low laser intensities by using a longer wavelength laser driver (e.g. a $10 \micro\meter$ CO$_2$ laser) due to its very large ponderomotive potential. On the other hand, short wavelength laser can produce electrons with very small residual momenta ($p_\perp\sim a_0\sim \sqrt{I}\lambda$) inside the wake, leading to electron beams with very small normalized emittances (tens of $\nano\meter$). Using particle-in-cell simulations we show that a $\sim10 \femto\second$ electron beam with $\sim4 \pico\coulomb$ of charge and a normalized emittance of $\sim 50 \nano\meter$ can be generated by combining a 10 $\micro\meter $ driving laser with a 400 $\nano\meter$ injection laser, which is an improvement of more than one order of magnitude compared to the typical results obtained when a single wavelength laser used for both the wake formation and ionization injection.
Degenerate four-wave mixing mediated by ponderomotive-force-driven plasma gratings is demonstrated in the near-infrared regime, which may be used to compensate for wavefront distortion occurring in various laser-plasma-based devices.
ABSTRACT We identify three regimes of correlated GeV-electron/keV-betatron-x-ray generation by a laser-plasma accelerator driven by the Texas Petawatt laser, and relate them to variations in strength of blowout, injection geometry and...
moreABSTRACT We identify three regimes of correlated GeV-electron/keV-betatron-x-ray generation by a laser-plasma accelerator driven by the Texas Petawatt laser, and relate them to variations in strength of blowout, injection geometry and beam loading.
We visualize ps-time-scale evolution of an electron density bubble--a wake structure created in atmospheric density plasma by an intense ultrashort laser pulse--from the phase "streak" that the bubble imprints onto a probe pulse...
moreWe visualize ps-time-scale evolution of an electron density bubble--a wake structure created in atmospheric density plasma by an intense ultrashort laser pulse--from the phase "streak" that the bubble imprints onto a probe pulse that crosses its path obliquely. Phase streaks, recovered in one shot using frequency-domain interferometric techniques, reveal the formation, propagation, and coalescence of the bubble within a 3 mm long ionized helium gas target. 3D particle-in-cell simulations validate the observed density-dependent bubble evolution, and correlate it with the generation of a quasimonoenergetic ∼ 100 MeV electron beam. The results provide a basis for understanding optimized electron acceleration at a plasma density n(e) ≈ 2 × 10(19) cm(-3), inefficient acceleration at lower density, and dephasing limits at higher density.
ABSTRACT We visualize formation, propagation and collapse of laser-driven plasma bubbles using a single-shot frequency domain streak camera, thereby identifying bubble dynamics that optimize electron injection and acceleration.
ABSTRACT We globally optimize a terawatt-laser-driven wakefield accelerator by systematically varying laser and target parameters to achieve 100 MeV monoenergetic electrons, <10% energy spread, 100 pC charge, <4 mrad...
moreABSTRACT We globally optimize a terawatt-laser-driven wakefield accelerator by systematically varying laser and target parameters to achieve 100 MeV monoenergetic electrons, <10% energy spread, 100 pC charge, <4 mrad divergence and 100% reproducibility.
ABSTRACT We report electron acceleration to 1.25 GeV by laser-driven wakefield acceleration at plasma density 5x1017 cm-3. Electron beams are dark-current-free, quasi-monoenergetic, highly collimated, contain tens of pC and have excellent...
moreABSTRACT We report electron acceleration to 1.25 GeV by laser-driven wakefield acceleration at plasma density 5x1017 cm-3. Electron beams are dark-current-free, quasi-monoenergetic, highly collimated, contain tens of pC and have excellent pointing stability.
ABSTRACT We report self-injected laser wakefield acceleration of electrons beyond 2 GeV in a uniform, 6 cm long undoped helium plasma of density 3-5E17 cm-3, driven by 150 fs laser pulses of up to 120 J from the Texas Petawatt Laser. The...
moreABSTRACT We report self-injected laser wakefield acceleration of electrons beyond 2 GeV in a uniform, 6 cm long undoped helium plasma of density 3-5E17 cm-3, driven by 150 fs laser pulses of up to 120 J from the Texas Petawatt Laser. The highest energy beams to date contain > 200 pC charge, with dN/dE peaking at as high as 2 GeV. At somewhat lower central energy (1.2 GeV), higher quality, dark-current-free beams with < 0.25 mrad FWHM divergence, ˜10 pC charge and ± 25% energy spread were obtained. Self-injected acceleration to > 1 GeV was observed at plasma density as low as 1.7E17 cm-3. Electrons were accompanied by X-rays from the betatron motion of the accelerating electrons. Analysis of shadows cast by tungsten wire fiducials positioned precisely in the paths of the magnetically dispersed electrons and of the betatron X-rays enabled electron energy at 2 GeV to be determined with ± 10% accuracy, without ambiguity due to electron launch angle variations. Simulations indicate that, with improvements in laser pulse focus quality, acceleration to 7 GeV is possible with the available pulse energy.
As an intense laser pulse propagates through an underdense plasma, the strong ponderomotive force pushes away the electrons and produces a trailing plasma bubble. In the meantime the pulse itself undergoes extreme nonlinear evolution that...
moreAs an intense laser pulse propagates through an underdense plasma, the strong ponderomotive force pushes away the electrons and produces a trailing plasma bubble. In the meantime the pulse itself undergoes extreme nonlinear evolution that results in strong spectral broadening toward the long-wavelength side. By experiment we demonstrate that this process can be utilized to generate ultrashort midinfrared pulses with an energy three orders of magnitude larger than that produced by crystal-based nonlinear optics. The infrared pulse is encapsulated in the bubble before exiting the plasma, hence is not absorbed by the plasma. The process is analyzed experimentally with laser-plasma tomographic measurements and numerically with three-dimensional particle-in-cell simulation. Good agreement is found between theoretical estimation, numerical simulation, and experimental results.
We demonstrate a single-shot method of visualizing the evolution of light-speed, laser-generated structures as they propagate over hundreds of Rayleigh lengths (typically ≥10 cm) through a tenuous medium. An ultrashort probe pulse crosses...
moreWe demonstrate a single-shot method of visualizing the evolution of light-speed, laser-generated structures as they propagate over hundreds of Rayleigh lengths (typically ≥10 cm) through a tenuous medium. An ultrashort probe pulse crosses the object's path at a small angle (θ<5°) and a specific time delay. Copies of the phase-modulated probe are then relay-imaged to separate detectors from selected object planes along the propagation path. A phase-contrast technique based on Kerr effect and nonlinear absorption converts phase to intensity modulation, improving sensitivity in tenuous media. A continuous record of the probe phase modulation along the propagation path is reconstructed.
X.Wang, R. Zgadzaj, W. Henderson, AS Yi, S. Kalmykov, V. Khudik, E. D'Avignon, P. Dong, N. Fazel, R. Korzekwa, Y.-Y. Chang, Hai-En Tsai, G. Dyer, E. Gaul, M. Martinez, T. Borger, F. Aymond, D. Hammond, R. Escamilla, S. Marijanovic,...
moreX.Wang, R. Zgadzaj, W. Henderson, AS Yi, S. Kalmykov, V. Khudik, E. D'Avignon, P. Dong, N. Fazel, R. Korzekwa, Y.-Y. Chang, Hai-En Tsai, G. Dyer, E. Gaul, M. Martinez, T. Borger, F. Aymond, D. Hammond, R. Escamilla, S. Marijanovic, G. Shvets, T. Ditmire, MC Downer Department of Physics, University of Texas at Austin, Austin TX, 78712
xwang08@physics.utexas.edu ... Abstract: We report observation of electron self-injection and acceleration in a plasma accelerator driven by the Texas petawatt laser at 1017 cm-3 plasma density, an order of magnitude ...
ABSTRACT We report self-injected quasi-monoenergetic (5% spread FWHM) acceleration of electrons to 2.0 ± 0.1 GeV by 0.6 PW-laser-driven wakefield acceleration in pure He plasma of density 5x10^17 cm^-3. Electron bunches diverge ~0.5mrad,...
moreABSTRACT We report self-injected quasi-monoenergetic (5% spread FWHM) acceleration of electrons to 2.0 ± 0.1 GeV by 0.6 PW-laser-driven wakefield acceleration in pure He plasma of density 5x10^17 cm^-3. Electron bunches diverge ~0.5mrad, and contain ~60 pC.
