Author: Chen, M.
Paper Title Page
MOP123 Colliding Pulse Injection Control in a Laser-Plasma Accelerator 325
 
  • C.G.R. Geddes, M. Chen, E. Esarey, W. Leemans, N.H. Matlis, D.E. Mittelberger, K. Nakamura, G.R.D. Plateau, C.B. Schroeder, C. Tóth
    LBNL, Berkeley, California, USA
  • D.L. Bruhwiler, J.R. Cary, E. Cormier-Michel, B.M. Cowan
    Tech-X, Boulder, Colorado, USA
 
  Funding: This work is supported by the U.S. Department of Energy, National Nuclear Security Administration, NA-22, and in part by the Office of Science under Contract No. DE-AC02-05CH11231.
Control of injection into a high gradient laser-plasma accelerator is presented using the beat between two ’colliding’ laser pulses to kick electrons into the plasma wake accelerating phase. Stable intersection and performance over hours of operation were obtained using active pointing control. Dependence of injector performance on laser and plasma parameters were characterized in coordination with simulations. By scanning the intersection point of the lasers, the injection position was controlled, mapping the acceleration length. Laser modifications to extend acceleration length are discussed towards production of tunable stable electron bunches as needed for applications including Thomson gamma sources and high energy colliders.
 
 
MOP137 Predictive Design and Interpretation of Colliding Pulse Injected Laser Wakefield Experiments 349
 
  • E. Cormier-Michel, D.L. Bruhwiler, B.M. Cowan, V.H. Ranjibar
    Tech-X, Boulder, Colorado, USA
  • M. Chen, E. Esarey, C.G.R. Geddes, W. Leemans, C.B. Schroeder
    LBNL, Berkeley, California, USA
 
  Funding: Work supported by DOE, NA-22, and Office of Science, HEP via the SciDAC-2 project ComPASS, grant No DE-FC02-07ER41499. Resources of NERSC were used (DOE contract No DE-AC02-05CH11231).
The use of colliding laser pulses to control the injection of plasma electrons into the plasma wake of a laser-plasma accelerator is a promising approach to obtain reproducible and tunable electron bunches with low energy spread and emittance. We present recent particle-in-cell simulations of colliding pulse injection for parameters relevant to ongoing experiments at LBNL. We perform parameter scans in order to determine the best conditions for the production of high quality electron bunches, and compare the results with experimental data. We also evaluate the effect of laser focusing in the plasma channel and of higher order laser mode components on the bunch properties.
 
 
MOP159 Ionization-Induced Trapping in Laser-Plasma Accelerators and Synchrotron Radiation from the Betatron Oscillation 394
 
  • M. Chen, E. Esarey, C.G.R. Geddes, W. Leemans, C.B. Schroeder
    LBNL, Berkeley, California, USA
  • D.L. Bruhwiler, E. Cormier-Michel
    Tech-X, Boulder, Colorado, USA
 
  Funding: This work is supported by the U.S. DOE Office of High Energy Physics under Contract No. DE-AC02-05CH11231, and NNSA, NA-22, and used the computational resources of NERSC.
Ionization injection into a laser wakefield accelerator is studied by multi-dimensional particle-in-cell (PIC) simulations. To obtain low energy spread beams we use a short region of gas mixture (H+N) near the start of the stage to trap electrons, while the remainder of the stage uses pure H and is injection-free. Effects of gas mix parameters, including concentration and length of the mixture region, on the final electron injection number and beam quality are studied. Two dimensional PIC simulations show the injected electron beam has filament structures in the plane perpendicular to the laser polarization direction in early time and this structure disappears later due to the betatron oscillation of the electrons in the wakefield. Synchrotron radiation from the accelerated electrons is calculated by a post processing code - Virtual Detector for Synchrotron Radiation (VDSR).