A5028235828- Laser-Plasma Interactions and Diagnostics
- Laser-Matter Interactions and Applications
- Laser Design and Applications
- Laser-induced spectroscopy and plasma
- Advanced Fiber Laser Technologies
- Particle Accelerators and Free-Electron Lasers
- Advanced X-ray Imaging Techniques
- Pulsed Power Technology Applications
- Atomic and Molecular Physics
- Solid State Laser Technologies
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Photorefractive and Nonlinear Optics
- Photonic Crystal and Fiber Optics
- Laser Material Processing Techniques
- Planetary Science and Exploration
- Diamond and Carbon-based Materials Research
- High-pressure geophysics and materials
- Advanced Surface Polishing Techniques
- Particle Detector Development and Performance
- Photochemistry and Electron Transfer Studies
- Digital Holography and Microscopy
- Advanced Electron Microscopy Techniques and Applications
- Luminescence Properties of Advanced Materials
- Image Processing Techniques and Applications
University of Oxford
2015-2024
Clarendon College
1990-2021
John Adams Institute for Accelerator Science
2016-2018
Isaac Newton Institute for Mathematical Sciences
2018
Max Planck Institute of Quantum Optics
2009
Ludwig-Maximilians-Universität München
2009
Stanford University
1995-1997
Royal Society
1997
Oxford Lasers (United Kingdom)
1992
We report guiding of laser pulses with peak input intensities greater than ${10}^{17}\text{ }\mathrm{W}\text{ }\mathrm{c}{\mathrm{m}}^{\mathrm{\ensuremath{-}}\mathrm{2}}$ in 30 mm and 50 long ${\mathrm{H}}_{\mathrm{2}}$-filled capillary discharge waveguides. Under conditions producing good the coupling propagation losses waveguide were $<4%$ $(7\ifmmode\pm\else\textpm\fi{}1)\text{ }{\mathrm{m}}^{\mathrm{\ensuremath{-}}\mathrm{1}}$, respectively. The spectra transmitted not broadened...
Laser-driven, quasimonoenergetic electron beams of up to approximately 200 MeV in energy have been observed from steady-state-flow gas cells. These emitted within a low-divergence cone 2.1+/-0.5 mrad FWHM display unprecedented shot-to-shot stability (2.5% rms), pointing (1.4 and charge (16% rms) owing highly reproducible gas-density profile the interaction volume. Laser-wakefield acceleration cells this type provides simple reliable source relativistic electrons suitable for applications...
Abstract This report presents the conceptual design of a new European research infrastructure EuPRAXIA. The concept has been established over last four years in unique collaboration 41 laboratories within Horizon 2020 study funded by Union. EuPRAXIA is first project that develops dedicated particle accelerator based on novel plasma acceleration concepts and laser technology. It focuses development electron accelerators underlying technologies, their user communities, exploitation existing...
A hydrogen plasma waveguide for high-intensity laser pulses is described. The guiding channel formed by a small-scale discharge in hydrogen-filled capillary. measured lifetime of the capillary inferred to be greater than 10(6) shots. results interferometric measurements electron density are presented. found highly ionized with an axial 2.7x10(18) cm(-3), and parabolic, curvature corresponding matched spot-size 37.5 microm.
A one-dimensional dissipative magnetohydrodynamics code is used to investigate the discharge dynamics of a waveguide for high-intensity laser pulses: gas-filled capillary waveguide. Simulations are performed conditions recent experimental measurement electron density profile in hydrogen-filled capillaries [D. J. Spence et al., Phys. Rev. E 63, 015401 (R) (2001)], and found be good agreement with those results. The evolution this device substantially different that Z-pinch discharges, owing...
We report experimental results on laser-driven electron acceleration with low divergence. The beam was generated by focussing 750 mJ, 42 fs laser pulses into a gas-filled capillary discharge waveguide at densities in the range between 10 18 and 19 cm 3 . Quasi-monoenergetic bunches energies as high 500 MeV have been detected, features reaching up to 1 GeV, albeit large shot-to-shot fluctuations. A more stable regime higher bunch charge (20-45 pC) less energy (200-300 MeV) could also be...
Selective enhancement ($>{10}^{3}$) of harmonics extending to the water window ($\ensuremath{\sim}4\text{ }\text{ }\mathrm{nm}$) generated in an argon gas filled straight bore capillary waveguide is demonstrated. This good agreement with modeling which indicates that multimode quasi-phase-matching achieved by rapid axial intensity modulations caused beating between fundamental and higher-order modes. Substantial pulse energies ($>10\text{ }\mathrm{nJ}$ per harmonic order) at wavelengths...
Laser wakefield accelerators can produce electric fields of order 10–100GV∕m, suitable for acceleration electrons to relativistic energies. The wakefields are excited by a relativistically intense laser pulse propagating through plasma and have phase velocity determined the group light pulse. Two important effects that limit distance hence net energy gain obtained an electron diffraction drive particle-wake dephasing. Diffraction focused ultrashort be overcome using preformed channels....
Transverse interferometric measurements are presented of the plasma channel formed in a hydrogen-filled capillary discharge waveguide recently used to generate 1 GeV electrons laser-driven accelerator for first time. The were found be good agreement with nonlocal thermal equilibrium simulations, but showed significant differences results quasistatic model developed by Bobrova et al. [Phys. Rev. E. 65, 016407 (2001)]. determine scaling laws axial electron density and matched spot size...
We investigate the influence of a tilted laser-pulse-intensity front on laser-wakefield acceleration. Such asymmetric light pulses may be exploited to obtain control over electron-bunch-pointing direction and in our case allowed for reproducible electron-beam steering an all-optical way within 8 mrad opening window with respect initial laser axis. also discovered evidence collective electron-betatron oscillations due off-axis electron injection into wakefield induced by pulse-front tilt....
Active plasma lensing is a compact technology for strong focusing of charged particle beams, which has gained considerable interest use in novel accelerator schemes. While providing $\mathrm{kT}/\mathrm{m}$ gradients, active lenses can have aberrations caused by radially nonuniform temperature profile, leading to degradation the beam quality. We present first direct measurement this aberration, consistent with theory, and show that it be fully suppressed changing from light gas species...
The Horizon 2020 Project EuPRAXIA ("European Plasma Research Accelerator with eXcellence In Applications") is preparing a conceptual design report of highly compact and cost-effective European facility multi-GeV electron beams using plasma as the acceleration medium. accelerator will be based on laser and/or beam driven approach used for photon science, high-energy physics (HEP) detector tests, other applications such X-ray sources medical imaging or material processing. started in November...
We present experiments and numerical simulations which demonstrate that fully ionized, low-density plasma channels could be formed by hydrodynamic expansion of columns produced optical field ionization. Simulations the in hydrogen an axicon lens show generation 200 mm long with axial densities order ${n}_{\mathrm{e}}(0)=1\ifmmode\times\else\texttimes\fi{}{10}^{17}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ lowest-order modes spot size...
The generation of quasimonoenergetic electron beams, with energies up to 200 MeV, by a laser-plasma accelerator driven in hydrogen-filled capillary discharge waveguide is investigated. Injection and acceleration electrons found depend sensitively on the delay between onset current arrival laser pulse. A comparison spectroscopic interferometric measurements suggests that injection assisted ionization atoms or ions within channel.
We demonstrate experimentally the resonant excitation of plasma waves by trains laser pulses. also take an important first step to achieving energy recovery accelerator showing that unused wakefield can be removed out-of-resonance trailing pulse. The measured wakefields are found in excellent agreement with analytical and numerical models linear regime. Our results indicate a promising direction for highly controlled, GeV-scale laser-plasma accelerators operating at multi-kilohertz...
A linear array of n calcite crystals is shown to allow the generation a high contrast (>10:1) train 2n energy (>100 μJ) pulses from single ultrafast laser pulse. Advantage taken pulse-splitting properties birefringent crystal, where an incident pulse can be split into two with orthogonal polarizations and equal intensity, separated temporally in proportion thickness crystal traversed difference refractive indices optic axes. In work presented here seven sequentially doubled used produce 128...
We describe a scheme for controlling electron injection into the quasilinear wakefield driven by guided drive pulse via ionization of dopant species collinear laser with short Rayleigh range. The is analyzed particle-in-cell simulations which show controlled and acceleration electrons to an energy 370 MeV, relative spread 2%, normalized transverse emittance $2.0\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$.
We present single-shot measurements of the longitudinal bunch profile from a laser-wakefield accelerator with sub-fs resolution, based on detection coherent transition radiation in broad spectral range. A previously developed phase retrieval algorithm enables reconstruction without prior assumptions about its shape. In this study, variable-length gas target is used to explore dynamics evolution. Our results show that once laser energy depleted time structure generated electron beam changes...
Laser-driven plasma accelerators can generate accelerating gradients three orders of magnitude larger than radio-frequency and have achieved beam energies above 1 GeV in centimetre long stages. However, the pulse repetition rate wall-plug efficiency laser is limited by driving to less approximately Hz 0.1% respectively. Here we investigate prospects for exciting wave with trains low-energy pulses rather a single high-energy pulse. Resonantly wakefield this way would enable use different...
Abstract Laser-plasma accelerators are capable of sustaining accelerating fields 10–100 GeV/m, 100–1000 times that conventional technology and the highest produced by any widely researched advanced accelerator concepts. also intrinsically accelerate short particle bunches, several orders magnitude shorter than technology, which leads to reductions in beamstrahlung and, hence, savings overall power consumption reach a desired luminosity. These properties make laser-plasma promising for more...
We describe the first demonstration of a collisionally excited optical-field-ionization laser driven within waveguide. Lasing on $4{d}^{9}5d\mathrm{\text{\ensuremath{-}}}4{d}^{9}5p$ transition at 41.8 nm in ${\mathrm{X}\mathrm{e}}^{8+}$ was observed to be closely correlated conditions under which pump pulses were guided well by gas-filled capillary discharge Simulations propagation radiation show that gain achieved over essentially whole 30 mm length