2011 Particle Accelerator Conference - List of Authors (Schroeder, C.B.)

Paper	Title	Page
MOP082	Modeling a 10 GeV Laser-Plasma Accelerator with INF&RNO	250
	C. Benedetti, E. Esarey, W. Leemans, C.B. Schroeder LBNL, Berkeley, California, USA
	Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The numerical modeling code INF&RNO (INtegrated Fluid & paRticle simulatioN cOde, pronounced "inferno") is an efficient 2D cylindrical code to model the interaction of a short laser pulse with an underdense plasma. The code is based on an envelope model for the laser while either a particle-in-cell (PIC) or a fluid description can be used for the plasma. The effect of the laser pulse on the plasma is modeled with the time-averaged ponderomotive force. These and other features allow for a significant speedup compared to standard full PIC simulations while still retaining physical fidelity. A boosted Lorentz frame (BLF) modeling capability has been introduced within the fluid framework enhancing the performance of the code. An example of a 10 GeV laser-plasma accelerator modeled using INF&RNO in the BLF is presented.

MOP083	Plasma Wake Excitation by Lasers or Particle Beams	253
	C.B. Schroeder, C. Benedetti, E. Esarey, C.G.R. Geddes, W. Leemans, C. Tóth LBNL, Berkeley, California, USA
	Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. Plasma wake excitation driven by lasers or particle beams is examined, and the implications of the different physical excitation mechanisms for accelerator design are discussed.

MOP124	Accurate Alignment of Plasma Channels Based on Laser Centroid Oscillations	328
	A.J. Gonsalves, C.G.R. Geddes, C. Lin, K. Nakamura, J. Osterhoff, C.B. Schroeder, S. Shiraishi, T. Sokollik, C. Tóth LBNL, Berkeley, California, USA E. Esarey University of Nevada, Reno, Reno, Nevada, USA W. Leemans UCB, Berkeley, California, USA
	Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. A technique has been developed to accurately align a laser beam through a plasma channel by minimizing the shift in laser centroid and angle at the channel outptut. If only the shift in centroid or angle is measured, then accurate alignment is provided by minimizing laser centroid motion at the channel exit as the channel properties are scanned. The improvement in alignment accuracy pro- vided by this technique is important for minimizing electron beam pointing errors in laser plasma accelerators.

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).

MOP161	Undulator-based Laser Wakefield Accelerator Electron Beam Diagnostic	397
	M.S. Bakeman, E. Esarey, W. Leemans, K. Nakamura, J. Osterhoff, K.E. Robinson, C.B. Schroeder, C. Tóth, J. van Tilborg LBNL, Berkeley, California, USA F.J. Grüner, R. Weingartner LMU, Garching, Germany
	Funding: This work is supported by DTRA and DOE-HEP. The design and current status of experiments to cou- ple the Tapered Hybrid Undulator (THUNDER) to the Lawrence Berkeley National Laboratory (LBNL) laser plasma accelerator (LPA) to measure electron beam energy spread and emittance are presented. * W.P. Leemans et al., Nature Physics, Volume 2, Issue 10, pp. 696-699 (2006). C.B. Schroeder et al., Proceedings AAC08 Conference (2008). * F. Grüner et al., Appl. Phys. B, 86(3):431–435 (2007).

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.

WEOBS1	The Berkeley Lab Laser Accelerator (BELLA): A 10 GeV Laser Plasma Accelerator	1416
	W. Leemans, R.M. Duarte, E. Esarey, D.S. Fournier, C.G.R. Geddes, D. Lockhart, C.B. Schroeder, C. Tóth, J.-L. Vay, S. Zimmermann LBNL, Berkeley, California, USA
	An overview is presented of the design of a 10 GeV laser plasma accelerator (LPA) that will be driven by a PW-class laser system and of the BELLA Project, under which the required Ti:sapphire laser system for the acceleration experiments is being installed. The basic design of the 10 GeV stage aims at operation in the quasi-linear regime, where the laser excited wakes are largely sinusoidal and allow acceleration of electrons and positrons. Simulations show that a 10 GeV electron beam can be generated in a meter scale plasma channel guided LPA operating at a density of about 10¹⁷ cm^-3 and powered by laser pulses containing 30-40 J of energy in a 50-200 fs duration pulse, focused to a spotsize of 50-100 micron. The lay-out of the facility and laser system will be presented as well as the progress on building the facility.

Paper

Title

Page

Modeling a 10 GeV Laser-Plasma Accelerator with INF&RNO

250

C. Benedetti, E. Esarey, W. Leemans, C.B. Schroeder
LBNL, Berkeley, California, USA

Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The numerical modeling code INF&RNO (INtegrated Fluid & paRticle simulatioN cOde, pronounced "inferno") is an efficient 2D cylindrical code to model the interaction of a short laser pulse with an underdense plasma. The code is based on an envelope model for the laser while either a particle-in-cell (PIC) or a fluid description can be used for the plasma. The effect of the laser pulse on the plasma is modeled with the time-averaged ponderomotive force. These and other features allow for a significant speedup compared to standard full PIC simulations while still retaining physical fidelity. A boosted Lorentz frame (BLF) modeling capability has been introduced within the fluid framework enhancing the performance of the code. An example of a 10 GeV laser-plasma accelerator modeled using INF&RNO in the BLF is presented.

MOP083

Plasma Wake Excitation by Lasers or Particle Beams

253

C.B. Schroeder, C. Benedetti, E. Esarey, C.G.R. Geddes, W. Leemans, C. Tóth
LBNL, Berkeley, California, USA

Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Plasma accelerators may be driven by the ponderomotive force of an intense laser or the space-charge force of a charged particle beam. Plasma wake excitation driven by lasers or particle beams is examined, and the implications of the different physical excitation mechanisms for accelerator design are discussed.

MOP124

Accurate Alignment of Plasma Channels Based on Laser Centroid Oscillations

328

A.J. Gonsalves, C.G.R. Geddes, C. Lin, K. Nakamura, J. Osterhoff, C.B. Schroeder, S. Shiraishi, T. Sokollik, C. Tóth
LBNL, Berkeley, California, USA
E. Esarey
University of Nevada, Reno, Reno, Nevada, USA
W. Leemans
UCB, Berkeley, California, USA

Funding: Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
A technique has been developed to accurately align a laser beam through a plasma channel by minimizing the shift in laser centroid and angle at the channel outptut. If only the shift in centroid or angle is measured, then accurate alignment is provided by minimizing laser centroid motion at the channel exit as the channel properties are scanned. The improvement in alignment accuracy pro- vided by this technique is important for minimizing electron beam pointing errors in laser plasma accelerators.

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).

MOP161

Undulator-based Laser Wakefield Accelerator Electron Beam Diagnostic

397

M.S. Bakeman, E. Esarey, W. Leemans, K. Nakamura, J. Osterhoff, K.E. Robinson, C.B. Schroeder, C. Tóth, J. van Tilborg
LBNL, Berkeley, California, USA
F.J. Grüner, R. Weingartner
LMU, Garching, Germany

Funding: This work is supported by DTRA and DOE-HEP.
The design and current status of experiments to cou- ple the Tapered Hybrid Undulator (THUNDER) to the Lawrence Berkeley National Laboratory (LBNL) laser plasma accelerator (LPA) to measure electron beam energy spread and emittance are presented.
* W.P. Leemans et al., Nature Physics, Volume 2, Issue 10, pp. 696-699 (2006).
** C.B. Schroeder et al., Proceedings AAC08 Conference (2008).
*** F. Grüner et al., Appl. Phys. B, 86(3):431–435 (2007).

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.

WEOBS1

The Berkeley Lab Laser Accelerator (BELLA): A 10 GeV Laser Plasma Accelerator

1416

W. Leemans, R.M. Duarte, E. Esarey, D.S. Fournier, C.G.R. Geddes, D. Lockhart, C.B. Schroeder, C. Tóth, J.-L. Vay, S. Zimmermann
LBNL, Berkeley, California, USA

An overview is presented of the design of a 10 GeV laser plasma accelerator (LPA) that will be driven by a PW-class laser system and of the BELLA Project, under which the required Ti:sapphire laser system for the acceleration experiments is being installed. The basic design of the 10 GeV stage aims at operation in the quasi-linear regime, where the laser excited wakes are largely sinusoidal and allow acceleration of electrons and positrons. Simulations show that a 10 GeV electron beam can be generated in a meter scale plasma channel guided LPA operating at a density of about 10¹⁷ cm^-3 and powered by laser pulses containing 30-40 J of energy in a 50-200 fs duration pulse, focused to a spotsize of 50-100 micron. The lay-out of the facility and laser system will be presented as well as the progress on building the facility.