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Full-Text Articles in Physics

Optical Control Of Electron Phase Space In Plasma Accelerators With Incoherently Stacked Laser Pulses, Serge Y. Kalmykov, Xavier Davoine, Remi Lehe, Agustin F. Lifschitz, Bradley A. Shadwick May 2015

Optical Control Of Electron Phase Space In Plasma Accelerators With Incoherently Stacked Laser Pulses, Serge Y. Kalmykov, Xavier Davoine, Remi Lehe, Agustin F. Lifschitz, Bradley A. Shadwick

Serge Youri Kalmykov

It is demonstrated that synthesizing an ultrahigh-bandwidth, negatively chirped laser pulse by incoherently stacking pulses of different wavelengths makes it possible to optimize the process of electron self-injection in a dense, highly dispersive plasma (n_0 \sim 10^{19} cm^{-3}). Avoiding transformation of the driving pulse into a relativistic optical shock maintains a quasi-monoenergetic electron spectrum through electron dephasing and boosts electron energy far beyond the limits suggested by existing scaling laws. In addition, evolution of the accelerating bucket in a plasma channel is shown to produce a background-free, tunable train of femtosecond-duration, 35 - 100 kA, time-synchronized quasi-monoenergetic electron bunches ...


Accordion Effect In Plasma Channels: Generation Of Tunable Comb-Like Electron Beams, Serge Y. Kalmykov, Bradley A. Shadwick, Isaac A. Ghebregziabher, Xavier Davoine, Remi Lehe, Agustin F. Lifschitz, Victor Malka May 2014

Accordion Effect In Plasma Channels: Generation Of Tunable Comb-Like Electron Beams, Serge Y. Kalmykov, Bradley A. Shadwick, Isaac A. Ghebregziabher, Xavier Davoine, Remi Lehe, Agustin F. Lifschitz, Victor Malka

Serge Youri Kalmykov

Propagating a short, relativistically intense laser pulse in a plasma channel makes it possible to generate comb-like electron beams for advanced radiation sources. The ponderomotive force of the leading edge of the pulse expels all electrons facing the pulse. The bare ions attract the ambient plasma electrons, forming a closed bubble of electron density confining the pulse tail. The cavity of electron density evolves slowly, in lock-step with the optical driver, and readily traps background electrons. The combination of a bubble (a self-consistently maintained, “soft” hollow channel) and a preformed channel forces transverse flapping of the laser pulse tail, causing ...


Physical Processes At Work In Sub-30fs, Pw Laser Pulse-Driven Plasma Accelerators: Towards Gev Electron Acceleration Experiments At Cilex Facility., Arnaud Beck, Serge Y. Kalmykov, Xavier Davoine, Agustin F. Lifschitz, Bradley A. Shadwick, Victor Malka, Arnd E. Specka Feb 2014

Physical Processes At Work In Sub-30fs, Pw Laser Pulse-Driven Plasma Accelerators: Towards Gev Electron Acceleration Experiments At Cilex Facility., Arnaud Beck, Serge Y. Kalmykov, Xavier Davoine, Agustin F. Lifschitz, Bradley A. Shadwick, Victor Malka, Arnd E. Specka

Serge Youri Kalmykov

Optimal regimes and physical processes at work are identified for the first round of laser wakefield acceleration experiments proposed at a future CILEX facility. The Apollon-10P CILEX laser, delivering fully compressed, near-PW-power pulses of sub-25 fs duration, is well suited for driving electron density wakes in the blowout regime in cm-length gas targets. Early destruction of the pulse (partly due to energy depletion)prevents electrons from reaching dephasing, limiting the energy gain to about 3 GeV. However, the optimal operating regimes, found with reduced and full three-dimensional particle-in-cell simulations, show high energy efficiency, with about 10%of incident pulse energy ...


All-Optical Control Of Electron Self-Injection In Millimeter-Scale, Tapered Dense Plasmas., Serge Y. Kalmykov, Xavier Davoine, Bradley A. Shadwick Feb 2014

All-Optical Control Of Electron Self-Injection In Millimeter-Scale, Tapered Dense Plasmas., Serge Y. Kalmykov, Xavier Davoine, Bradley A. Shadwick

Serge Youri Kalmykov

It is demonstrated that a laser pulse with an ultrahigh bandwidth (400 nm) is an asset for future high-repetition-rate , quasimonoenergetic (QME), GeV-scale laser plasma electron accelerators. Manipulating the phase of the driver has a direct impact on evolution of the accelerating bucket (a cavity of electron density maintained by the pressure of the laser pulse radiation), making it possible to control electron self-injection and the final parameters of the QME beam by purely optical means. The large bandwidth makes it possible to compensate for the frequency red-shift accumulated at the pulse leading edge in transit through the plasma. Advancing higher ...


All-Optical Control Of Electron Trapping In Plasma Channels, Serguei Y. Kalmykov, Bradley A. Shadwick, Xavier Davoine Sep 2013

All-Optical Control Of Electron Trapping In Plasma Channels, Serguei Y. Kalmykov, Bradley A. Shadwick, Xavier Davoine

Serge Youri Kalmykov

The accelerating bucket of a laser-plasma accelerator (a cavity of electron density maintained by the laser pulse radiation pressure) evolves slowly, in lock-step with the optical driver, and readily traps background electrons. The trapping process can thus be controlled by purely optical means. Sharp gradients in the nonlinear refractive index produce a large frequency red-shift, localized at the leading edge of the pulse. Negative group velocity dispersion associated with the plasma response compresses the laser pulse into a relativistic optical shock (ROS), slowing the pulse (and the bucket), reducing the electron dephasing length, and limiting energy gain. Even more importantly ...


Dark-Current-Free Laser-Plasma Acceleration In Blowout Regime Using Nonlinear Plasma Lens, Serguei Y. Kalmykov Jan 2013

Dark-Current-Free Laser-Plasma Acceleration In Blowout Regime Using Nonlinear Plasma Lens, Serguei Y. Kalmykov

Serge Youri Kalmykov

It is demonstrated that a thin dense plasma slab (lens), placed before a multi-centimeter-length, low-density plasma (accelerator), overfocuses an incident petawatt laser pulse at a controlled location inside the accelerator, creating an expanding electron density bubble that traps plasma electrons over a brief time interval. As soon as the pulse stabilizes and self-guiding begins, the bubble stabilizes and transforms into the first (non-broken) bucket of a conventional three-dimensional nonlinear plasma wave, eliminating any chance for further injection. A well collimated, quasi-monoenergetic electron bunch with a zero low-energy background further accelerates to a multi-GeV energy.


Sub-Millimeter-Scale, 100-Mev-Class Quasi-Monoenergetic Laser Plasma Accelerator Based On All-Optical Control Of Dark Current In The Blowout Regime, Serguei Y. Kalmykov, Xavier Davoine, Bradley A. Shadwick Dec 2012

Sub-Millimeter-Scale, 100-Mev-Class Quasi-Monoenergetic Laser Plasma Accelerator Based On All-Optical Control Of Dark Current In The Blowout Regime, Serguei Y. Kalmykov, Xavier Davoine, Bradley A. Shadwick

Serge Youri Kalmykov

It is demonstrated that by negatively chirping the frequency of a 20-fs, 15-TW driving laser pulse with an ultrabroad bandwidth (corresponding to a sub-2-cycle transform-limited duration it is possible to prevent early compression of the pulse into an optical shock, thus reducing expansion of the accelerating plasma bucket (electron density "bubble") and delaying dephasing of self-injected and accelerated electrons. These features help suppress unwanted continuous self-injection (dark current) in the blowout regime, making possible to use the entire dephasing length to generate low-background, quasi-monoenergetic 200-MeV-scale electron beams from sub-mm-length, dense plasmas (n_{e0} = 1.3 x 10^{19} cm^{−3}).


Computationally Efficient Methods For Modelling Laser Wakefield Acceleration In The Blowout Regime, Benjamin M. Cowan, Serguei Y. Kalmykov, Arnaud Beck, Xavier Davoine, Kyle Bunkers, Agustin F. Lifschitz, Erik Lefebvre, David L. Bruhwiler, Bradley A. Shadwick, Donald P. Umstadter Jun 2012

Computationally Efficient Methods For Modelling Laser Wakefield Acceleration In The Blowout Regime, Benjamin M. Cowan, Serguei Y. Kalmykov, Arnaud Beck, Xavier Davoine, Kyle Bunkers, Agustin F. Lifschitz, Erik Lefebvre, David L. Bruhwiler, Bradley A. Shadwick, Donald P. Umstadter

Donald P. Umstadter

Electron self-injection and acceleration until dephasing in the blowout regime is studied for a set of initial conditions typical of recent experiments with 100-terawatt-class lasers. Two different approaches to computationally efficient, fully explicit, 3D particle-in-cell modelling are examined. First, the Cartesian code VORPAL (Nieter, C. and Cary, J. R. 2004 VORPAL: a versatile plasma simulation code. J. Comput. Phys. 196, 538) using a perfect-dispersion electromagnetic solver precisely describes the laser pulse and bubble dynamics, taking advantage of coarser resolution in the propagation direction, with a proportionally larger time step. Using third-order splines for macroparticles helps suppress the sampling noise while ...


Computationally Efficient Methods For Modelling Laser Wakefield Acceleration In The Blowout Regime, Benjamin M. Cowan, Serguei Y. Kalmykov, Arnaud Beck, Xavier Davoine, Kyle Bunkers, Agustin F. Lifschitz, Erik Lefebvre, David L. Bruhwiler, Bradley A. Shadwick, Donald P. Umstadter Jun 2012

Computationally Efficient Methods For Modelling Laser Wakefield Acceleration In The Blowout Regime, Benjamin M. Cowan, Serguei Y. Kalmykov, Arnaud Beck, Xavier Davoine, Kyle Bunkers, Agustin F. Lifschitz, Erik Lefebvre, David L. Bruhwiler, Bradley A. Shadwick, Donald P. Umstadter

Serge Youri Kalmykov

Electron self-injection and acceleration until dephasing in the blowout regime is studied for a set of initial conditions typical of recent experiments with 100-terawatt-class lasers. Two different approaches to computationally efficient, fully explicit, 3D particle-in-cell modelling are examined. First, the Cartesian code VORPAL (Nieter, C. and Cary, J. R. 2004 VORPAL: a versatile plasma simulation code. J. Comput. Phys. 196, 538) using a perfect-dispersion electromagnetic solver precisely describes the laser pulse and bubble dynamics, taking advantage of coarser resolution in the propagation direction, with a proportionally larger time step. Using third-order splines for macroparticles helps suppress the sampling noise while ...


Laser Plasma Acceleration With A Negatively Chirped Pulse: All-Optical Control Over Dark Current In The Blowout Regime, Serguei Y. Kalmykov, Arnaud Beck, Xavier Davoine, Erik Lefebvre, Bradley A. Shadwick Mar 2012

Laser Plasma Acceleration With A Negatively Chirped Pulse: All-Optical Control Over Dark Current In The Blowout Regime, Serguei Y. Kalmykov, Arnaud Beck, Xavier Davoine, Erik Lefebvre, Bradley A. Shadwick

Serge Youri Kalmykov

Recent experiments with 100 terawatt-class, sub-50 femtosecond laser pulses show that electrons self-injected into a laser-driven electron density bubble can be accelerated above 0.5 gigaelectronvolt energy in a sub-centimetre length rarefied plasma. To reach this energy range, electrons must ultimately outrun the bubble and exit the accelerating phase; this, however, does not ensure high beam quality. Wake excitation increases the laser pulse bandwidth by red-shifting its head, keeping the tail unshifted. Anomalous group velocity dispersion of radiation in plasma slows down the red-shifted head, compressing the pulse into a few-cycle-long piston of relativistic intensity. Pulse transformation into a piston ...


Physics Of Quasi-Monoenergetic Laser-Plasma Acceleration Of Electrons In The Blowout Regime, Serguei Y. Kalmykov, Bradley A. Shadwick, Arnaud Beck, Erik Lefebvre Oct 2011

Physics Of Quasi-Monoenergetic Laser-Plasma Acceleration Of Electrons In The Blowout Regime, Serguei Y. Kalmykov, Bradley A. Shadwick, Arnaud Beck, Erik Lefebvre

Serge Youri Kalmykov

No abstract provided.


Electron Self-Injection Into An Evolving Plasma Bubble: Quasi-Monoenergetic Laser-Plasma Acceleration In The Blowout Regime, Serguei Y. Kalmykov, Arnaud Beck, Sunghwan A. Yi, Vladimir N. Khudik, Michael C. Downer, Erik Lefebvre, Bradley A. Shadwick, Donald P. Umstadter Apr 2011

Electron Self-Injection Into An Evolving Plasma Bubble: Quasi-Monoenergetic Laser-Plasma Acceleration In The Blowout Regime, Serguei Y. Kalmykov, Arnaud Beck, Sunghwan A. Yi, Vladimir N. Khudik, Michael C. Downer, Erik Lefebvre, Bradley A. Shadwick, Donald P. Umstadter

Donald P. Umstadter

An electron density bubble driven in a rarefied uniform plasma by a slowly evolving laser pulse goes through periods of adiabatically slow expansions and contractions. Bubble expansion causes robust self-injection of initially quiescent plasma electrons, whereas stabilization and contraction terminate self-injection thus limiting injected charge; concomitant phase space rotation reduces the bunch energy spread. In regimes relevant to experiments with hundred terawatt- to petawatt-class lasers, bubble dynamics and, hence, the self-injection process are governed primarily by the driver evolution. Collective transverse fields of the trapped electron bunch reduce the accelerating gradient and slow down phase space rotation. Bubble expansion followed ...


Electron Self-Injection Into An Evolving Plasma Bubble: Quasi-Monoenergetic Laser-Plasma Acceleration In The Blowout Regime, Serguei Y. Kalmykov, Arnaud Beck, Sunghwan A. Yi, Vladimir N. Khudik, Michael C. Downer, Erik Lefebvre, Bradley A. Shadwick, Donald P. Umstadter Apr 2011

Electron Self-Injection Into An Evolving Plasma Bubble: Quasi-Monoenergetic Laser-Plasma Acceleration In The Blowout Regime, Serguei Y. Kalmykov, Arnaud Beck, Sunghwan A. Yi, Vladimir N. Khudik, Michael C. Downer, Erik Lefebvre, Bradley A. Shadwick, Donald P. Umstadter

Serge Youri Kalmykov

An electron density bubble driven in a rarefied uniform plasma by a slowly evolving laser pulse goes through periods of adiabatically slow expansions and contractions. Bubble expansion causes robust self-injection of initially quiescent plasma electrons, whereas stabilization and contraction terminate self-injection thus limiting injected charge; concomitant phase space rotation reduces the bunch energy spread. In regimes relevant to experiments with hundred terawatt- to petawatt-class lasers, bubble dynamics and, hence, the self-injection process are governed primarily by the driver evolution. Collective transverse fields of the trapped electron bunch reduce the accelerating gradient and slow down phase space rotation. Bubble expansion followed ...


Dark-Current-Free Petawatt Laser-Driven Wakefield Accelerator Based On Electron Self-Injection Into An Expanding Plasma Bubble, Serguei Y. Kalmykov, Sunghwan A. Yi, Arnaud Beck, Agustin F. Lifschitz, Xavier Davoine, Erik Lefebvre, Vladimir N. Khudik, Gennady Shvets, Michael C. Downer Dec 2010

Dark-Current-Free Petawatt Laser-Driven Wakefield Accelerator Based On Electron Self-Injection Into An Expanding Plasma Bubble, Serguei Y. Kalmykov, Sunghwan A. Yi, Arnaud Beck, Agustin F. Lifschitz, Xavier Davoine, Erik Lefebvre, Vladimir N. Khudik, Gennady Shvets, Michael C. Downer

Serge Youri Kalmykov

A dark-current-free plasma accelerator driven by a short (~ 150 fs) self-guided petawatt laser pulse is proposed. The accelerator uses two plasma layers, one of which, short and dense, acts as a thin nonlinear lens. It is followed by a long rarefied plasma (~ 10^{17} electrons cm^{−3}) in which background electrons are trapped and accelerated by a nonlinear laser wakefield. The pulse overfocused by the plasma lens diffracts in low-density plasma as in vacuum and drives in its wake a rapidly expanding electron density bubble. The expanding bubble effectively traps initially quiescent electrons. The trapped charge given by quasi-cylindrical three-dimensional ...


Hamiltonian Analysis Of Electron Self-Injection And Acceleration Into An Evolving Plasma Bubble, Sunghwan A. Yi, Vladimir N. Khudik, Serguei Y. Kalmykov, Gennady Shvets Dec 2010

Hamiltonian Analysis Of Electron Self-Injection And Acceleration Into An Evolving Plasma Bubble, Sunghwan A. Yi, Vladimir N. Khudik, Serguei Y. Kalmykov, Gennady Shvets

Serge Youri Kalmykov

Injection and acceleration of the background plasma electrons in laser wakefield accelerators (LWFA) operated in the blowout (‘bubble’) regime are analysed. Using a model of a slowly expanding spherical plasma bubble propagating with an ultra-relativistic speed, we derive a sufficient condition for the electron injection: the change in the electron’s Hamiltonian in the co-moving with the bubble reference frame must exceed its rest mass energy m_{e}c^2. We demonstrate the existence of the minimal expansion rate of the bubble needed for electron injection. We demonstrate that if the bubble’s expansion is followed by its stabilization or ...


Electron Self-Injection Into An Evolving Plasma Bubble: The Way To A Dark Current Free Gev-Scale Laser Accelerator, Serguei Y. Kalmykov, Arnaud Beck, Sunghwan A. Yi, Vladimir N. Khudik, Bradley A. Shadwick, Erik Lefebvre, Michael C. Downer Nov 2010

Electron Self-Injection Into An Evolving Plasma Bubble: The Way To A Dark Current Free Gev-Scale Laser Accelerator, Serguei Y. Kalmykov, Arnaud Beck, Sunghwan A. Yi, Vladimir N. Khudik, Bradley A. Shadwick, Erik Lefebvre, Michael C. Downer

Serge Youri Kalmykov

A time-varying electron density bubble created by the radiation pressure of a tightly focused petawatt laser pulse traps electrons of ambient rarefied plasma and accelerates them to a GeV energy over a few-cm distance. Expansion of the bubble caused by the shape variation of the self-guided pulse is the primary cause of electron self-injection in strongly rarefied plasmas (n_0 ~ 10^{17} cm^{−3}). Stabilization and contraction of the bubble extinguishes the injection. After the bubble stabilization, longitudinal non-uniformity of the accelerating gradient results in a rapid phase space rotation that produces a quasi-monoenergetic bunch well before the de-phasing limit. Combination ...


Numerical Modelling Of A 10-Cm-Long Multi-Gev Laser Wakefield Accelerator Driven By A Self-Guided Petawatt Pulse, Serguei Y. Kalmykov, Sunghwan A. Yi, Arnaud Beck, Agustin F. Lifschitz, Xavier Davoine, Erik Lefebvre, Alexander Pukhov, Vladimir N. Khudik, Gennady Shvets, Steven A. Reed, Peng Dong, Xiaoming Wang, Dongsu Du, Stefan Bedacht, Rafal B. Zgadzaj, Watson Henderson, Aaron Bernstein, Gilliss Dyer, Mikael Martinez, Erhard Gaul, Todd Ditmire, Michael C. Downer Apr 2010

Numerical Modelling Of A 10-Cm-Long Multi-Gev Laser Wakefield Accelerator Driven By A Self-Guided Petawatt Pulse, Serguei Y. Kalmykov, Sunghwan A. Yi, Arnaud Beck, Agustin F. Lifschitz, Xavier Davoine, Erik Lefebvre, Alexander Pukhov, Vladimir N. Khudik, Gennady Shvets, Steven A. Reed, Peng Dong, Xiaoming Wang, Dongsu Du, Stefan Bedacht, Rafal B. Zgadzaj, Watson Henderson, Aaron Bernstein, Gilliss Dyer, Mikael Martinez, Erhard Gaul, Todd Ditmire, Michael C. Downer

Serge Youri Kalmykov

The use of a short-pulse petawatt (PW) laser (sub-200 fs duration, ~ 1 micron wavelength) enables experimental realization of a self-guided, multicentimetre-long multi-GeV laser wakefield electron accelerator. A comprehensive set of numerical simulations showed that a 150 fs, 1.33 PW pulse is self- guided over 10 cm of a static filling gaseous plasma of density 1–3 x 10^{17} cm^{−3} and is stable against relativistic filamentation. A fully broken electromagnetic wake (electron density ‘bubble’) is excited over the entire interaction length. Variations of bubble size and shape associated with nonlinear evolution of the driving pulse result in self-injection ...


Electron Self-Injection And Trapping Into An Evolving Plasma Bubble, Serguei Y. Kalmykov, Sunghwan A. Yi, Vladimir N. Khudik, Gennady Shvets Sep 2009

Electron Self-Injection And Trapping Into An Evolving Plasma Bubble, Serguei Y. Kalmykov, Sunghwan A. Yi, Vladimir N. Khudik, Gennady Shvets

Serge Youri Kalmykov

The blowout (or bubble) regime of laser wakefield acceleration is promising for generating monochromatic high-energy electron beams out of low-density plasmas. It is shown analytically and by particle-in-cell simulations that self-injection of the background plasma electrons into the quasistatic plasma bubble can be caused by slow temporal expansion of the bubble. Sufficient criteria for the electron trapping and bubble’s expansion rate are derived using a semianalytic nonstationary Hamiltonian theory. It is further shown that the combination of bubble’s expansion and contraction results in monoenergetic electron beams.


Injection, Trapping, And Acceleration Of Electrons In A Three-Dimensional Nonlinear Laser Wakefield, Serguei Y. Kalmykov, Leonid M. Gorbunov, Patrick Mora, Gennady Shvets Oct 2006

Injection, Trapping, And Acceleration Of Electrons In A Three-Dimensional Nonlinear Laser Wakefield, Serguei Y. Kalmykov, Leonid M. Gorbunov, Patrick Mora, Gennady Shvets

Serge Youri Kalmykov

It is demonstrated that the accelerating and focusing phases of the nonlinear three-dimensional axisymmetric laser wake can almost entirely overlap starting from a certain distance behind the laser pulse in homogeneous plasma. Such field structure results from the curvature of phase fronts due to the radially inhomogeneous relativistic shift of plasma frequency. Consequently, the number of trapped low-energy electrons can be much greater than that predicted by the linear wake theory. This effect is favorable for quasi-monoenergetic acceleration of a considerable charge (several hundreds of pC) to about 1 GeV per electron in the plasma wakefield driven by an ultrashort ...


Laser Wakefield Acceleration By Petawatt Ultrashort Laser Pulses, Leonid M. Gorbunov, Serguei Y. Kalmykov, Patrick Mora Feb 2005

Laser Wakefield Acceleration By Petawatt Ultrashort Laser Pulses, Leonid M. Gorbunov, Serguei Y. Kalmykov, Patrick Mora

Serge Youri Kalmykov

An ultrashort (about 30 fs) petawatt laser pulse focused with a wide focal spot (about 100 mm) in a rarefied plasma (n_0 ~ 10^{17} cm^{−3}) excites a nonlinear plasma wakefield which can accelerate injected electrons up to GeV energies without any pulse channeling. Under these conditions, propagation of the laser pulse with an overcritical power for relativistic self-focusing is almost the same as in vacuum. The nonlinear quasiplane plasma wave, whose amplitude and phase velocity vary along the laser path, effectively traps and accelerates injected electrons with a wide range of initial energies. Electrons accelerated over two Rayleigh lengths ...