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Nanomechanical testing of silica nanospheres for levitated optomechanics experiments
Authors:
Cayla R. Harvey,
Evan Weisman,
Chethn Galla,
Ryan Danenberg,
Qiyuan Hu,
Swati Singh,
Andrew A. Geraci,
Siddhartha Pathak
Abstract:
Optically-levitated dielectric particles can serve as ultra-sensitive detectors of feeble forces and torques, as tools for use in quantum information science, and as a testbed for quantum coherence in macroscopic systems. Knowledge of the structural and optical properties of the particles is important for calibrating the sensitivity of such experiments. Here we report the results of nanomechanical…
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Optically-levitated dielectric particles can serve as ultra-sensitive detectors of feeble forces and torques, as tools for use in quantum information science, and as a testbed for quantum coherence in macroscopic systems. Knowledge of the structural and optical properties of the particles is important for calibrating the sensitivity of such experiments. Here we report the results of nanomechanical testing of silica nanospheres and investigate an annealing approach which can produce closer to bulk-like behavior in the samples in terms of their elastic moduli. These results, combined with our experimental investigations of optical trap lifetimes in high vacuum at high trapping-laser intensity for both annealed and as-grown nanospheres, were used to provide a theoretical analysis of the effects of porosity and non-sphericity in the samples, identifying possible mechanisms of trapping instabilities for nanospheres with non-bulk-silica-like properties.
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Submitted 3 August, 2022;
originally announced August 2022.
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In Situ Characterization of Ultraintense Laser Pulses
Authors:
C. N. Harvey
Abstract:
We present a method for determining the characteristics of an intense laser pulse by probing it with a relativistic electron beam. After an initial burst of very high-energy $γ$-radiation the electrons proceed to emit a series of attosecond duration X-ray pulses as they leave the field. These flashes provide detailed information about the interaction, allowing us to determine properties of the las…
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We present a method for determining the characteristics of an intense laser pulse by probing it with a relativistic electron beam. After an initial burst of very high-energy $γ$-radiation the electrons proceed to emit a series of attosecond duration X-ray pulses as they leave the field. These flashes provide detailed information about the interaction, allowing us to determine properties of the laser pulse: something that is currently a challenge for ultra-high intensity laser systems.
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Submitted 17 November, 2018; v1 submitted 17 July, 2018;
originally announced July 2018.
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Quantifying how much sensory information in a neural code is relevant for behavior
Authors:
Giuseppe Pica,
Eugenio Piasini,
Houman Safaai,
Caroline A. Runyan,
Mathew E. Diamond,
Tommaso Fellin,
Christoph Kayser,
Christopher D. Harvey,
Stefano Panzeri
Abstract:
Determining how much of the sensory information carried by a neural code contributes to behavioral performance is key to understand sensory function and neural information flow. However, there are as yet no analytical tools to compute this information that lies at the intersection between sensory coding and behavioral readout. Here we develop a novel measure, termed the information-theoretic inter…
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Determining how much of the sensory information carried by a neural code contributes to behavioral performance is key to understand sensory function and neural information flow. However, there are as yet no analytical tools to compute this information that lies at the intersection between sensory coding and behavioral readout. Here we develop a novel measure, termed the information-theoretic intersection information $I_{II}(S;R;C)$, that quantifies how much of the sensory information carried by a neural response R is used for behavior during perceptual discrimination tasks. Building on the Partial Information Decomposition framework, we define $I_{II}(S;R;C)$ as the part of the mutual information between the stimulus S and the response R that also informs the consequent behavioral choice C. We compute $I_{II}(S;R;C)$ in the analysis of two experimental cortical datasets, to show how this measure can be used to compare quantitatively the contributions of spike timing and spike rates to task performance, and to identify brain areas or neural populations that specifically transform sensory information into choice.
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Submitted 6 December, 2017;
originally announced December 2017.
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Experimental evidence of radiation reaction in the collision of a high-intensity laser pulse with a laser-wakefield accelerated electron beam
Authors:
J. M. Cole,
K. T. Behm,
T. G. Blackburn,
J. C. Wood,
C. D. Baird,
M. J. Duff,
C. Harvey,
A. Ilderton,
A. S. Joglekar,
K. Krushelnik,
S. Kuschel,
M. Marklund,
P. McKenna,
C. D. Murphy,
K. Poder,
C. P. Ridgers,
G. M. Samarin,
G. Sarri,
D. R. Symes,
A. G. R. Thomas,
J. Warwick,
M. Zepf,
Z. Najmudin,
S. P. D. Mangles
Abstract:
The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation reaction. When interacting with a high-energy electron beam, today's lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We report on the o…
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The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation reaction. When interacting with a high-energy electron beam, today's lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We report on the observation of radiation reaction in the collision of an ultra-relativistic electron beam generated by laser wakefield acceleration ($\varepsilon > 500$ MeV) with an intense laser pulse ($a_0 > 10$). We measure an energy loss in the post-collision electron spectrum that is correlated with the detected signal of hard photons ($γ$-rays), consistent with a quantum (stochastic) description of radiation reaction. The generated $γ$-rays have the highest energies yet reported from an all-optical inverse Compton scattering scheme, with critical energy $\varepsilon_{\rm crit} > $ 30 MeV.
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Submitted 4 January, 2018; v1 submitted 21 July, 2017;
originally announced July 2017.
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Quantum quenching of radiation losses in short laser pulses
Authors:
Chris Harvey,
Arkady Gonoskov,
Anton Ilderton,
Mattias Marklund
Abstract:
Accelerated charges radiate, and therefore must lose energy. The impact of this energy loss on particle motion, called radiation reaction, becomes significant in intense-laser matter interactions, where it can reduce collision energies, hinder particle acceleration schemes, and is seemingly unavoidable. Here we show that this common belief breaks down in short laser pulses, and that energy losses…
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Accelerated charges radiate, and therefore must lose energy. The impact of this energy loss on particle motion, called radiation reaction, becomes significant in intense-laser matter interactions, where it can reduce collision energies, hinder particle acceleration schemes, and is seemingly unavoidable. Here we show that this common belief breaks down in short laser pulses, and that energy losses and radiation reaction can be controlled and effectively switched off by appropriate tuning of the pulse length. This "quenching" of emission is impossible in classical physics, but becomes possible in QED due to the discrete nature of quantum emissions.
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Submitted 12 February, 2017; v1 submitted 27 June, 2016;
originally announced June 2016.
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Focussing effects in laser-electron Thomson scattering
Authors:
C. Harvey,
M. Marklund,
A. R. Holkundkar
Abstract:
We study the effects of laser pulse focussing on the spectral properties of Thomson scattered radiation. Modelling the laser as a paraxial beam we find that, in all but the most extreme cases of focussing, the temporal envelope has a much bigger effect on the spectrum than the focussing itself. For the case of ultra-short pulses, where the paraxial model is no longer valid, we adopt a sub-cycle ve…
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We study the effects of laser pulse focussing on the spectral properties of Thomson scattered radiation. Modelling the laser as a paraxial beam we find that, in all but the most extreme cases of focussing, the temporal envelope has a much bigger effect on the spectrum than the focussing itself. For the case of ultra-short pulses, where the paraxial model is no longer valid, we adopt a sub-cycle vector beam description of the field. It is found that the emission harmonics are blue shifted and broaden out in frequency space as the pulse becomes shorter. Additionally the carrier envelope phase becomes important, resulting in an angular asymmetry in the spectrum. We then use the same model to study the effects of focussing beyond the limit where the paraxial expansion is valid. It is found that fields focussed to sub-wavelength spot sizes produce spectra that are qualitatively similar to those from sub-cycle pulses due to the shortening of the pulse with focussing. Finally, we study high-intensity fields and find that, in general, the focussing makes negligible difference to the spectra in the regime of radiation reaction.
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Submitted 31 July, 2016; v1 submitted 18 June, 2016;
originally announced June 2016.
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Recurrent Network Models Of Sequence Generation And Memory
Authors:
Kanaka Rajan,
Christopher D Harvey,
David W Tank
Abstract:
Sequential activation of neurons is a common feature of network activity during a variety of behaviors, including working memory and decision making. Previous network models for sequences and memory emphasized specialized architectures in which a principled mechanism is pre-wired into their connectivity. Here we demonstrate that, starting from random connectivity and modifying a small fraction of…
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Sequential activation of neurons is a common feature of network activity during a variety of behaviors, including working memory and decision making. Previous network models for sequences and memory emphasized specialized architectures in which a principled mechanism is pre-wired into their connectivity. Here we demonstrate that, starting from random connectivity and modifying a small fraction of connections, a largely disordered recur- rent network can produce sequences and implement working memory efficiently. We use this process, called Partial In-Network Training (PINning), to model and match cellular resolution imaging data from the posterior parietal cortex during a virtual memory- guided two-alternative forced-choice task. Analysis of the connectivity reveals that sequences propagate by the cooperation between recurrent synaptic interactions and external inputs, rather than through feedforward or asymmetric connections. Together our results suggest that neural sequences may emerge through learning from largely unstructured network architectures.
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Submitted 14 March, 2016;
originally announced March 2016.
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Quantum radiation reaction: from interference to incoherence
Authors:
Victor Dinu,
Chris Harvey,
Anton Ilderton,
Mattias Marklund,
Greger Torgrimsson
Abstract:
We investigate quantum radiation reaction in laser-electron interactions across different energy and intensity regimes. Using a fully quantum approach which also accounts exactly for the effect of the strong laser pulse on the electron motion, we identify in particular a regime in which radiation reaction is dominated by quantum interference. We find signatures of quantum radiation reaction in the…
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We investigate quantum radiation reaction in laser-electron interactions across different energy and intensity regimes. Using a fully quantum approach which also accounts exactly for the effect of the strong laser pulse on the electron motion, we identify in particular a regime in which radiation reaction is dominated by quantum interference. We find signatures of quantum radiation reaction in the electron spectra which have no classical analogue and which cannot be captured by the incoherent approximations typically used in the high-intensity regime. These signatures are measurable with presently available laser and accelerator technology.
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Submitted 30 January, 2016; v1 submitted 13 December, 2015;
originally announced December 2015.
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Propagation of Ultra-Intense Laser Pulses in Near-critical Plasmas: Depletion Mechanisms and Effects of Radiation Reaction
Authors:
Erik Wallin,
Arkady Gonoskov,
Christopher Harvey,
Olle Lundh,
Mattias Marklund
Abstract:
Although, for current laser pulse energies, the weakly nonlinear regime of LWFA is known to be the optimal for reaching the highest possible electron energies, the capabilities of upcoming large laser systems will provide the possibility of running highly nonlinear regimes of laser pulse propagation in underdense or near-critical plasmas. Using an extended particle-in-cell (PIC) model that takes i…
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Although, for current laser pulse energies, the weakly nonlinear regime of LWFA is known to be the optimal for reaching the highest possible electron energies, the capabilities of upcoming large laser systems will provide the possibility of running highly nonlinear regimes of laser pulse propagation in underdense or near-critical plasmas. Using an extended particle-in-cell (PIC) model that takes into account all the relevant physics, we show that such regimes can be implemented with external guiding for a relatively long distance of propagation and allow for the stable transformation of laser energy into other types of energy, including the kinetic energy of a large number of high energy electrons and their incoherent emission of photons. This is despite the fact that the high intensity of the laser pulse triggers a number of new mechanisms of energy depletion, which we investigate systematically.
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Submitted 5 April, 2017; v1 submitted 10 December, 2015;
originally announced December 2015.
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Thomson scattering in high-intensity chirped laser pulses
Authors:
Amol R. Holkundkar,
Chris Harvey,
Mattias Marklund
Abstract:
We consider the Thomson scattering of an electron in an ultra-intense chirped laser pulse. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion of its original energy. This results in a significant enhancement of the energy and intensity of the emitted radiation as compared to the case without chi…
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We consider the Thomson scattering of an electron in an ultra-intense chirped laser pulse. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion of its original energy. This results in a significant enhancement of the energy and intensity of the emitted radiation as compared to the case without chirping.
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Submitted 29 July, 2015;
originally announced July 2015.
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Narrowing of the emission angle in high-intensity Compton scattering
Authors:
C. N. Harvey,
A. Gonoskov,
M. Marklund,
E. Wallin
Abstract:
We consider the emission spectrum of high-energy electrons in an intense laser field. At high intensities ($a_0\sim200$) we find that the QED theory predicts a narrower angular spread of emissions than the classical theory. This is due to the classical theory overestimating the energy loss of the particles, resulting in them becoming more susceptible to reflection in the laser pulse.
We consider the emission spectrum of high-energy electrons in an intense laser field. At high intensities ($a_0\sim200$) we find that the QED theory predicts a narrower angular spread of emissions than the classical theory. This is due to the classical theory overestimating the energy loss of the particles, resulting in them becoming more susceptible to reflection in the laser pulse.
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Submitted 21 December, 2015; v1 submitted 23 July, 2015;
originally announced July 2015.
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Lighting up the Christmas tree: high-intensity laser interactions with a nano-structured target
Authors:
A. Gonoskov,
C. Harvey,
A. Ilderton,
F. Mackenroth,
M. Marklund
Abstract:
We perform a numerical study of the interaction of a high-intensity laser pulse with a nano-structured target. In particular, we study a target where the nano-structuring increases the absorption rate as compared to the flat target case. The transport of electrons within the target, and in particular in the nano-structure, is analysed. It is shown that it is indeed possible, using a terawatt class…
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We perform a numerical study of the interaction of a high-intensity laser pulse with a nano-structured target. In particular, we study a target where the nano-structuring increases the absorption rate as compared to the flat target case. The transport of electrons within the target, and in particular in the nano-structure, is analysed. It is shown that it is indeed possible, using a terawatt class laser, to light up a nano-scale Christmas tree. Due to the form of the tree we achieve very strong edge fields, in particular at the top where the star is located. Such edge fields, as here located at ion rich spots, makes strong acceleration gradients possible. It also results in a nice, warm glow suitable for the holiday season.
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Submitted 17 December, 2014;
originally announced December 2014.
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SIMLA: Simulating laser-particle interactions via classical and quantum electrodynamics
Authors:
D. G. Green,
C. N. Harvey
Abstract:
We present the Fortran code SIMLA, which is designed for the study of charged particle dynamics in laser and other background fields. This can be done classically via the Landau-Lifshitz equation, or alternatively, via the simulation of photon emission events determined by strong-field quantum-electrodynamics amplitudes and implemented using Monte-Carlo type routines. Multiple laser fields can be…
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We present the Fortran code SIMLA, which is designed for the study of charged particle dynamics in laser and other background fields. This can be done classically via the Landau-Lifshitz equation, or alternatively, via the simulation of photon emission events determined by strong-field quantum-electrodynamics amplitudes and implemented using Monte-Carlo type routines. Multiple laser fields can be included in the simulation and the propagation direction, beam shape (plane wave, focussed paraxial, constant crossed, or constant magnetic), and time envelope of each can be independently specified.
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Submitted 15 October, 2014;
originally announced October 2014.
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Testing numerical implementations of strong field electrodynamics
Authors:
C. N. Harvey,
A. Ilderton,
B. King
Abstract:
We test current numerical implementations of laser-matter interactions by comparison with exact analytical results. Focussing on photon emission processes, it is found that the numerics accurately reproduce analytical emission spectra in all considered regimes, except for the harmonic structures often singled out as the most significant high intensity/multi-photon effects. We find that this discre…
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We test current numerical implementations of laser-matter interactions by comparison with exact analytical results. Focussing on photon emission processes, it is found that the numerics accurately reproduce analytical emission spectra in all considered regimes, except for the harmonic structures often singled out as the most significant high intensity/multi-photon effects. We find that this discrepancy originates in the use of the locally constant field approximation.
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Submitted 22 September, 2014;
originally announced September 2014.
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Ultra-high brilliance multi-MeV $γ$-ray beam from non-linear Thomson scattering
Authors:
G. Sarri,
D. J. Corvan,
W. Schumaker,
J. Cole,
A. Di Piazza,
H. Ahmed,
C. Harvey,
C. H. Keitel,
K. Krushelnick,
S. P. D. Mangles,
Z. Najmudin,
D. Symes,
A. G. R. Thomas,
M. Yeung,
Z. Zhao,
M. Zepf
Abstract:
We report on the generation of a narrow divergence ($θ\approx 2.5$ mrad), multi-MeV ($E_\text{MAX} = 18$ MeV) and ultra-high brilliance ($\approx 2\times10^{19}$ photons s$^{-1}$ mm$^{-2}$ mrad $^{-2}$ 0.1\% BW) $γ$-ray beam from the scattering of an ultra-relativistic laser-wakefield accelerated electron beam in the field of a relativistically intense laser (dimensionless amplitude $a_0\approx2$)…
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We report on the generation of a narrow divergence ($θ\approx 2.5$ mrad), multi-MeV ($E_\text{MAX} = 18$ MeV) and ultra-high brilliance ($\approx 2\times10^{19}$ photons s$^{-1}$ mm$^{-2}$ mrad $^{-2}$ 0.1\% BW) $γ$-ray beam from the scattering of an ultra-relativistic laser-wakefield accelerated electron beam in the field of a relativistically intense laser (dimensionless amplitude $a_0\approx2$). The spectrum of the generated $γ$-ray beam is measured, with MeV resolution, seamlessly from 6 MeV to 18 MeV, giving clear evidence of the onset of non-linear Thomson scattering. The photon source has the highest brilliance in the multi-MeV regime ever reported in the literature.
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Submitted 25 July, 2014;
originally announced July 2014.
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Magnetic mirror cavities as THz radiation sources and a means of quantifying radiation friction
Authors:
Amol R. Holkundkar,
Chris Harvey
Abstract:
We propose a radiation source based on a magnetic mirror cavity. Relativistic electrons are simulated entering the cavity and their trajectories and resulting emission spectra are calculated. The uniformity of the particle orbits is found to result in a frequency comb in terahertz range, the precise energies of which are tuneable by varying the electron's $γ$-factor. For very high energy particles…
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We propose a radiation source based on a magnetic mirror cavity. Relativistic electrons are simulated entering the cavity and their trajectories and resulting emission spectra are calculated. The uniformity of the particle orbits is found to result in a frequency comb in terahertz range, the precise energies of which are tuneable by varying the electron's $γ$-factor. For very high energy particles radiation friction causes the spectral harmonics to broaden and we suggest this as a possible way to verify competing classical equations of motion.
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Submitted 2 June, 2014;
originally announced June 2014.
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Detecting radiation reaction at moderate laser intensities
Authors:
Thomas Heinzl,
Chris Harvey,
Anton Ilderton,
Mattias Marklund,
Stepan S. Bulanov,
Sergey Rykovanov,
Carl B. Schroeder,
Eric Esarey,
Wim P. Leemans
Abstract:
We propose a new method of detecting radiation reaction effects in the motion of particles subjected to laser pulses of moderate intensity and long duration. The effect becomes sizeable for particles that gain almost no energy through the interaction with the laser pulse.
We propose a new method of detecting radiation reaction effects in the motion of particles subjected to laser pulses of moderate intensity and long duration. The effect becomes sizeable for particles that gain almost no energy through the interaction with the laser pulse.
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Submitted 1 October, 2013;
originally announced October 2013.
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Transverse spreading of electrons in high-intensity laser fields
Authors:
D. G. Green,
C. N. Harvey
Abstract:
We show that for collisions of electrons with a high-intensity laser, discrete photon emissions introduce a transverse beam spread which is distinct from that due to classical (or beam shape) effects. Via numerical simulations, we show that this quantum induced transverse momentum gain of the electron is manifest in collisions with a realistic laser pulse of intensity within reach of current techn…
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We show that for collisions of electrons with a high-intensity laser, discrete photon emissions introduce a transverse beam spread which is distinct from that due to classical (or beam shape) effects. Via numerical simulations, we show that this quantum induced transverse momentum gain of the electron is manifest in collisions with a realistic laser pulse of intensity within reach of current technology, and we propose it as a measurable signature of strong-field quantum electrodynamics.
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Submitted 18 March, 2014; v1 submitted 31 July, 2013;
originally announced July 2013.
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Anomalous radiative trapping in laser fields of extreme intensity
Authors:
A. Gonoskov,
A. Bashinov,
I. Gonoskov,
C. Harvey,
A. Ilderton,
A. Kim,
M. Marklund,
G. Mourou,
A. Sergeev
Abstract:
We demonstrate that charged particles in a sufficiently intense standing wave are compressed toward, and oscillate synchronously at, the maxima of the electric field. This unusual trapping behaviour, which we call 'anomalous radiative trapping' (ART), opens up new possibilities for the generation of radiation and particle beams, both of which are high-energy, directed and collimated. ART also prov…
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We demonstrate that charged particles in a sufficiently intense standing wave are compressed toward, and oscillate synchronously at, the maxima of the electric field. This unusual trapping behaviour, which we call 'anomalous radiative trapping' (ART), opens up new possibilities for the generation of radiation and particle beams, both of which are high-energy, directed and collimated. ART also provides a mechanism for particle control in high-intensity QED experiments.
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Submitted 6 August, 2013; v1 submitted 24 June, 2013;
originally announced June 2013.
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Probing nonperturbative QED with optimally focused laser pulses
Authors:
A. Gonoskov,
I. Gonoskov,
C. Harvey,
A. Ilderton,
A. Kim,
M. Marklund,
G. Mourou,
A. M. Sergeev
Abstract:
We study nonperturbative pair production in intense, focused laser fields called e-dipole pulses. We address the conditions required, such as the quality of the vacuum, for reaching high intensities without initiating beam-depleting cascades, the number of pairs which can be created, and experimental detection of the created pairs. We find that e-dipole pulses offer an optimal method of investigat…
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We study nonperturbative pair production in intense, focused laser fields called e-dipole pulses. We address the conditions required, such as the quality of the vacuum, for reaching high intensities without initiating beam-depleting cascades, the number of pairs which can be created, and experimental detection of the created pairs. We find that e-dipole pulses offer an optimal method of investigating nonperturbative QED.
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Submitted 26 July, 2013; v1 submitted 19 February, 2013;
originally announced February 2013.
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The intensity dependent mass shift: existence, universality and detection
Authors:
Chris Harvey,
Thomas Heinzl,
Anton Ilderton,
Mattias Marklund
Abstract:
The electron mass shift in a laser field has long remained an elusive concept. We show that the mass shift can exist in pulses but that it is neither unique nor universal: it can be reduced by pulse shaping. We show also that the detection of mass shift effects in laser-particle scattering experiments is feasible with current technology, even allowing for the transverse structure of realistic beam…
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The electron mass shift in a laser field has long remained an elusive concept. We show that the mass shift can exist in pulses but that it is neither unique nor universal: it can be reduced by pulse shaping. We show also that the detection of mass shift effects in laser-particle scattering experiments is feasible with current technology, even allowing for the transverse structure of realistic beams.
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Submitted 11 June, 2012; v1 submitted 27 March, 2012;
originally announced March 2012.
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Computer Simulation of Cytoskeleton-Induced Blebbing in Lipid Membranes
Authors:
Eric J. Spangler,
Cameron W. Harvey,
Joel D. Revalee,
P. B. Sunil Kumar,
Mohamed Laradji
Abstract:
Blebs are balloon-shaped membrane protrusions that form during many physiological processes. Using computer simulation of a particle-based model for self-assembled lipid bilayers coupled to an elastic meshwork, we investigated the phase behavior and kinetics of blebbing. We found that blebs form for large values of the ratio between the areas of the bilayer and the cytoskeleton. We also found that…
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Blebs are balloon-shaped membrane protrusions that form during many physiological processes. Using computer simulation of a particle-based model for self-assembled lipid bilayers coupled to an elastic meshwork, we investigated the phase behavior and kinetics of blebbing. We found that blebs form for large values of the ratio between the areas of the bilayer and the cytoskeleton. We also found that blebbing can be induced when the cytoskeleton is subject to a localized ablation or a uniform compression. The results obtained are qualitatively in agreement with the experimental evidence and the model opens up the possibility to study the kinetics of bleb formation in detail.
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Submitted 25 October, 2011;
originally announced October 2011.
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Radiation damping in pulsed Gaussian beams
Authors:
Chris Harvey,
Mattias Marklund
Abstract:
We consider the effects of radiation damping on the electron dynamics in a Gaussian beam model of a laser field. For high intensities, i.e. with dimensionless intensity a0 \gg 1, it is found that the dynamics divide into three regimes. For low energy electrons (low initial γ-factor, γ0) the radiation damping effects are negligible. At higher energies, but still at 2γ0 < a0, the damping alters the…
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We consider the effects of radiation damping on the electron dynamics in a Gaussian beam model of a laser field. For high intensities, i.e. with dimensionless intensity a0 \gg 1, it is found that the dynamics divide into three regimes. For low energy electrons (low initial γ-factor, γ0) the radiation damping effects are negligible. At higher energies, but still at 2γ0 < a0, the damping alters the final displacement and the net energy change of the electron. For 2γ0 > a0 one is in a regime of radiation reaction induced electron capture. This capture is found to be stable with respect to the spatial properties of the electron beam and results in a significant energy loss of the electrons. In this regime the plane wave model of the laser field provides a good description of the dynamics, whereas for lower energies the Gaussian beam and plane wave models differ significantly. Finally the dynamics are considered for the case of an XFEL field. It is found that the significantly lower intensities of such fields inhibits the damping effects.
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Submitted 5 October, 2011;
originally announced October 2011.
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Signatures of Radiation Reaction in Ultra-Intense Laser Fields
Authors:
C. Harvey,
T. Heinzl,
M. Marklund
Abstract:
We discuss radiation reaction effects on charges propagating in ultra-intense laser fields. Our analysis is based on an analytic solution of the Landau-Lifshitz equation. We suggest to measure radiation reaction in terms of a symmetry breaking parameter associated with the violation of null translation invariance in the direction opposite to the laser beam. As the Landau-Lifshitz equation is nonli…
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We discuss radiation reaction effects on charges propagating in ultra-intense laser fields. Our analysis is based on an analytic solution of the Landau-Lifshitz equation. We suggest to measure radiation reaction in terms of a symmetry breaking parameter associated with the violation of null translation invariance in the direction opposite to the laser beam. As the Landau-Lifshitz equation is nonlinear the energy transfer within the pulse is rather sensitive to initial conditions. This is elucidated by comparing colliding and fixed target modes in electron laser collisions.
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Submitted 4 October, 2011;
originally announced October 2011.
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Covariant Worldline Numerics for Charge Motion with Radiation Reaction
Authors:
C. Harvey,
T. Heinzl,
N. Iji,
K. Langfeld
Abstract:
We develop a numerical formulation to calculate the classical motion of charges in strong electromagnetic fields, such as those occurring in high-intensity laser beams. By reformulating the dynamics in terms of SL(2,C) matrices representing the Lorentz group, our formulation maintains explicit covariance, in particular the mass-shell condition. Considering an electromagnetic plane wave field where…
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We develop a numerical formulation to calculate the classical motion of charges in strong electromagnetic fields, such as those occurring in high-intensity laser beams. By reformulating the dynamics in terms of SL(2,C) matrices representing the Lorentz group, our formulation maintains explicit covariance, in particular the mass-shell condition. Considering an electromagnetic plane wave field where the analytic solution is known as a test case, we demonstrate the effectiveness of the method for solving both the Lorentz force and the Landau-Lifshitz equations. The latter, a second order reduction of the Lorentz-Abraham-Dirac equation, describes radiation reaction without the usual pathologies.
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Submitted 14 December, 2010;
originally announced December 2010.
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Signatures of High-Intensity Compton Scattering
Authors:
Chris Harvey,
Thomas Heinzl,
Anton Ilderton
Abstract:
We review known and discuss new signatures of high-intensity Compton scattering assuming a scenario where a high-power laser is brought into collision with an electron beam. At high intensities one expects to see a substantial red-shift of the usual kinematic Compton edge of the photon spectrum caused by the large, intensity dependent, effective mass of the electrons within the laser beam. Emiss…
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We review known and discuss new signatures of high-intensity Compton scattering assuming a scenario where a high-power laser is brought into collision with an electron beam. At high intensities one expects to see a substantial red-shift of the usual kinematic Compton edge of the photon spectrum caused by the large, intensity dependent, effective mass of the electrons within the laser beam. Emission rates acquire their global maximum at this edge while neighbouring smaller peaks signal higher harmonics. In addition, we find that the notion of the centre-of-mass frame for a given harmonic becomes intensity dependent. Tuning the intensity then effectively amounts to changing the frame of reference, going continuously from inverse to ordinary Compton scattering with the centre-of-mass kinematics defining the transition point between the two.
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Submitted 24 March, 2009;
originally announced March 2009.
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Vortex solitons in an off-resonant Raman medium
Authors:
A. V. Gorbach,
D. V. Skryabin,
C. N. Harvey
Abstract:
We investigate existence and linear stability of coupled vortex solitons supported by cascaded four-wave mixing in a Raman active medium excited away from the resonance. We present a detailed analysis for the two- and three-component vortex solitons and demonstrate the formation of stable and unstable vortex solitons, and associated spatio-temporal helical beams, under the conditions of the simu…
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We investigate existence and linear stability of coupled vortex solitons supported by cascaded four-wave mixing in a Raman active medium excited away from the resonance. We present a detailed analysis for the two- and three-component vortex solitons and demonstrate the formation of stable and unstable vortex solitons, and associated spatio-temporal helical beams, under the conditions of the simultaneous frequency and vortex comb generation.
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Submitted 8 May, 2008;
originally announced May 2008.