Abstract
Xray generation by many charged particles experiencing accelerations similar to those in laser wakefield accelerator experiments, including the effects of the interaction of the laser pulse with trapped electrons, as well as betatron oscillations in an electroncavity, is directly evaluated. Semianalytic calculations of high energy photons are performed by solving classical spectral integrals for x rays produced by the combined action of a laser pulse and the fields of an electroncavity in an underdense plasma. Angularly resolved power spectra for electron bunches accelerated in the combined electromagnetic fields due to a Gaussian laser field and a paraboloid potential due to an electroncavity are calculated using a semianalytic numerical algorithm to explicitly calculate the well known spectral integrals. The laser polarizes the resulting xrayradiation. In addition to the high energy photons due to the betatron oscillations, lower energy radiation is emitted in a conical emission pattern due to the coherent addition of radiation from the linear acceleration of the electrons in the wakefield.
The author acknowledges the OSIRIS consortium (UCLA, USC, IST) for the use of OSIRIS and Stefan Kniep for useful discussions.
I. INTRODUCTION
II. THE MODEL AND NUMERICAL METHODS
III. NUMERICAL RESULTS
A. Radiation spectra due to a single electron
B. Spectra due to a 16 pC electron bunch
IV. CONCLUSIONS
Key Topics
 Polarization
 24.0
 Betatrons
 21.0
 Electron beams
 17.0
 Synchrotron radiation
 15.0
 Coherent radiation
 9.0
Figures
Electron number density (image) and electrostatic potential, (white contours), normalized to from a twodimensional particleincell simulation using the code OSIRIS (Ref. 27). Data are taken at a time into the simulation, with initial conditions , , and .
Electron number density (image) and electrostatic potential, (white contours), normalized to from a twodimensional particleincell simulation using the code OSIRIS (Ref. 27). Data are taken at a time into the simulation, with initial conditions , , and .
Schematic of the coordinate system for collecting radiation. is the observation direction.
Schematic of the coordinate system for collecting radiation. is the observation direction.
The Lorentz factor as a function of time of a single electron accelerated in a plasma bubble with normalized potential , radius , and initial transverse momenta , .
The Lorentz factor as a function of time of a single electron accelerated in a plasma bubble with normalized potential , radius , and initial transverse momenta , .
The radiated spectral intensity, of a single electron accelerated in a plasma bubble with normalized potential , radius , and initial transverse momenta , and displacements , .
The radiated spectral intensity, of a single electron accelerated in a plasma bubble with normalized potential , radius , and initial transverse momenta , and displacements , .
The radiated spectral intensity, of a single electron accelerated in a plasma bubble with normalized potential , radius , with , and various initial transverse momenta: (a) , , perpendicular polarization. (b) , , parallel polarization. (c) , , perpendicular polarization. (d) , , parallel polarization. (e) , , perpendicular polarization. (f) , , parallel polarization.
The radiated spectral intensity, of a single electron accelerated in a plasma bubble with normalized potential , radius , with , and various initial transverse momenta: (a) , , perpendicular polarization. (b) , , parallel polarization. (c) , , perpendicular polarization. (d) , , parallel polarization. (e) , , perpendicular polarization. (f) , , parallel polarization.
The radiated spectral intensity, of a single electron accelerated in a plasma bubble with normalized potential , radius with , and various initial transverse momenta: (a) , , parallel polarization. (b) , , parallel polarization. (c) , , parallel polarization. (The perpendicular component is exactly zero in all cases.)
The radiated spectral intensity, of a single electron accelerated in a plasma bubble with normalized potential , radius with , and various initial transverse momenta: (a) , , parallel polarization. (b) , , parallel polarization. (c) , , parallel polarization. (The perpendicular component is exactly zero in all cases.)
The radiated spectral intensity, of a single electron accelerated in a plasma bubble with normalized potential , radius , and initial transverse displacements of , . The bunch interacted with the copropagating laser with a normalized average vector potential of , group velocity of , linear polarization, and various phase velocities and momenta: (a) , , , , perpendicular polarization. (b) , , , , parallel polarization. (c) , , , , perpendicular polarization. (d) , , , , parallel polarization. (e) , , , , perpendicular polarization. (f) , , , , parallel polarization.
The radiated spectral intensity, of a single electron accelerated in a plasma bubble with normalized potential , radius , and initial transverse displacements of , . The bunch interacted with the copropagating laser with a normalized average vector potential of , group velocity of , linear polarization, and various phase velocities and momenta: (a) , , , , perpendicular polarization. (b) , , , , parallel polarization. (c) , , , , perpendicular polarization. (d) , , , , parallel polarization. (e) , , , , perpendicular polarization. (f) , , , , parallel polarization.
Trajectory of a single electron accelerated in a plasma bubble with normalized potential , radius , initial transverse momenta , interacting with a laser pulse with polarized in the direction.
Trajectory of a single electron accelerated in a plasma bubble with normalized potential , radius , initial transverse momenta , interacting with a laser pulse with polarized in the direction.
Starting positions of 1000 particles, superimposed on an image of the wake potential and a contour plot of laser intensity envelope. The spatial scales are in units of .
Starting positions of 1000 particles, superimposed on an image of the wake potential and a contour plot of laser intensity envelope. The spatial scales are in units of .
The total radiated energy from 1000 electrons accelerated in a plasma bubble with normalized potential , radius as a function of for the laser pulse.
The total radiated energy from 1000 electrons accelerated in a plasma bubble with normalized potential , radius as a function of for the laser pulse.
The radiated spectral intensity, , due to 1000 macroparticles, representing , accelerated in a plasma bubble with normalized potential , radius . The initial displacements of the particles, , , were distributed with a Gaussian probability in a distribution function with widths at of transverse to propagation and in the direction of propagation. The initial transverse momenta of the macroparticles were also assigned with a Gaussian probability, with a width of . The bunch interacted with the copropagating laser with a group velocity of , linear polarization, and phase velocity : (a) , perpendicular polarization, (b) , parallel polarization, (b) , perpendicular polarization, (c) , parallel polarization, (d) , perpendicular polarization, and (e) , parallel polarization.
The radiated spectral intensity, , due to 1000 macroparticles, representing , accelerated in a plasma bubble with normalized potential , radius . The initial displacements of the particles, , , were distributed with a Gaussian probability in a distribution function with widths at of transverse to propagation and in the direction of propagation. The initial transverse momenta of the macroparticles were also assigned with a Gaussian probability, with a width of . The bunch interacted with the copropagating laser with a group velocity of , linear polarization, and phase velocity : (a) , perpendicular polarization, (b) , parallel polarization, (b) , perpendicular polarization, (c) , parallel polarization, (d) , perpendicular polarization, and (e) , parallel polarization.
The angular distribution of radiation emitted (a) with no laser present, (b) perpendicular to laser polarization, and (c) parallel to laser polarization corresponding to images (c)–(f) in Fig. 11. The inset graph shows the same distributions but normalized to their peak values, with the same color coding.
The angular distribution of radiation emitted (a) with no laser present, (b) perpendicular to laser polarization, and (c) parallel to laser polarization corresponding to images (c)–(f) in Fig. 11. The inset graph shows the same distributions but normalized to their peak values, with the same color coding.
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