07 Plasma Accelerator Schemes
Paper Title Page
TUSBC1
 Simulating Radiation from Laser-wakefield Accelerators  
 
  • A.D. Debus, M.H. Bussmann, R. Pausch, U. Schramm, R. Widera
    Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany
  
  Radiation from laser-wakefield accelerators (LWFA), ranging from the x-ray to the infrared spectrum, is of great interest for experiments, both for advanced diagnostics and radiation sources. Hence, detailed numerical modelling of these phenomena is desired for understanding measured data. In order to meet computational demands, we build on recent advances in general purpose graphical processing units (GPGPU). With the PIConGPU code, a scalable, highly-parallel, performant implementation of a 3D-PIC code [1], it is possible to run large-scale, realistic simulations within hours compared to more than a week on CPUs. Here we present, a Liénard-Wiechert-type radiation algorithm (CLARA) as an extension to PIConGPU, which now can calculate the plasma radiation spectrum in all directions of the solid angle, parallel to the laser-plasma simulation, when the full macro-particle data is in memory. We discuss the algorithm with its trade-offs between data storage and computation time on GPUs and CPUs. As examples, we display first results from realistic laser-wakefield accelerator scenarios investigated using the DRACO laser system at the HZDR.
[1] H Burau, et al, "PIConGPU: A Fully Relativistic Particle-in-Cell Code for a GPU Cluster", IEEE Transactions on Plasma Science 38(10), 2831-2839 (October 2010) 		 
slides icon Slides TUSBC1 [10.019 MB]  
 
TUSBC2 Low Noise Particle-in-Cell Simulations of Laser Plasma Accelerator 10 GeV Stages 78
 
  • E. Cormier-Michel, D.L. Bruhwiler, J.R. Cary, B.M. Cowan, E.J. Hallman
    Tech-X, Boulder, Colorado, USA
  • E. Esarey, C.G.R. Geddes, W. Leemans, C.B. Schroeder, J.-L. Vay
    LBNL, Berkeley, California, USA
  
  Funding: Work supported by DOE/HEP, under grants DE-SC0004441 and DE-FC02-07ER41499, including use of NERSC under DE-AC02-05CH11231.
Because of their ultra-high accelerating gradient, laser plasma based accelerators (LPA) are contemplated for the next generation of high-energy colliders and light sources. The upcoming BELLA project will explore acceleration of electron bunches to 10 GeV in a 1 meter long plasma, where a wakefield is driven by a PW-class laser. Particle-in-cell (PIC) simulations are used to design the upcoming experiments where boosted frame simulations are used to model the full scale stages. As criteria on energy spread and beam emittance become more stringent, PIC simulations become more challenging as high frequency noise artificially increases those quantities. We show that calculating the beam self-fields using a static Poisson solve in the beam frame dramatically reduces particle noise, allowing for more accurate simulation of the beam evolution. In particular, this method gets correct cancellation of the transverse self-electric and magnetic fields of the beam, eliminating artificial self-forces, which is usually not true when using the standard PIC algorithm based on the staggered (“Yee”) electromagnetic field solver. 		 
slides icon Slides TUSBC2 [5.989 MB]  
 
TUSBC3
 Improved Particle Statistics for Laser-Plasma Self-Injection Simulations  
 
  • B.M. Cowan, D.L. Bruhwiler
    Tech-X, Boulder, Colorado, USA
  • J.R. Cary
    CIPS, Boulder, Colorado, USA
  • K. Kyle, S. Serguei, B. Shadwick, D.P. Umstadter
    UNL, Lincoln, USA
  
  Funding: Work supported by Contracts DOE DE-SC0006245, DE-FC02-07ER41499, DE-FG02-08ER55000, and DE-FG02-05ER15663; NSF PHY-1104683; DTRA HDTRA1-11-C-0001; and AFOSR FA9550-11-1-0157 and 9550-08-1-0232.
Simulations of laser-plasma acceleration (LPA) play a key role in understanding the effect of initial conditions on injected beam parameters. Here we present a method for improving the accuracy of simulated particle beams from the LPA self-injection process. We recently demonstrated the ability to compute the collection volume of an injection process – the range of initial locations of injected particles*. We find that the collection volume consists of an annular region around the propagation axis. By loading this region with higher particle statistics than in other locations, we can significantly increase the number of macroparticles in the injected beam. We show that this technique captures much finer detail of particle phase space than does uniform loading, and results in lower noise. We demonstrate convergence of key beam parameters in 2D, and present results of full 3D simulations. In addition, we present results of a novel technique in which particles can deform and split if they expand, effectively self-generating statistics. We also discuss a perfect dispersion algorithm and its impact on self-injection results.
*B. M. Cowan et al., "Computationally efficient methods for modelling laser wakefield acceleration in the blowout regime," accepted for publication in J. Plasma Phys. (2012) 		 
slides icon Slides TUSBC3 [6.516 MB]  
 
THAAI2 Efficient Modeling of Laser-plasma Accelerators Using the Ponderomotive-based Code INF&RNO 206
 
  • 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.
Numerical modeling of laser-plasma accelerators using the ponderomotive approximation allows efficient modeling of 10 GeV and beyond laser-plasma accelerators. The time-averaged ponderomotive force approximation also allows simulation in cylindrical geometry which captures relevant 3D physics at 2D computational cost. In this talk I will present the code INF&RNO (INtegrated Fluid & paRticle simulatioN cOde). The code is based on an envelope model for the laser while either a 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 poderomotive force. These and other features, such as dynamical resampling of the phase space distribution to reduce on-axis noise and boosted-Lorentz-frame modeling capability, allow for a speedup of several orders of magnitude compared to standard full PIC simulations while still retaining physical fidelity. The code has been benchmarked against analytical solutions and 3D PIC simulations and a set of validation tests together with a discussion of the performances will be presented. Applications to the BELLA PW laser-plasma accelerator experiments at LBNL will be discussed. 		 
slides icon Slides THAAI2 [1.881 MB]  
 
THP08 Beam Dynamics Studies for Particle Driven Plasma Wakefield Acceleration Experiments at PITZ 236
 
  • M. Khojoyan, M. Groß, G. Klemz, G. Koss, M. Krasilnikov, A. Oppelt, F. Stephan
    DESY Zeuthen, Zeuthen, Germany
  • M. Khojoyan
    ANSL, Yerevan, Armenia
  
  The Photo Injector Test Facility at DESY, Zeuthen site (PITZ) is developing and optimizing high brightness electron sources for linac based free electron lasers such as FLASH and the European XFEL. The high quality of the 25 MeV electron beam together with the availability of a highly flexible photocathode laser system makes the PITZ injector a perfect facility for variety of experimental studies. Two approaches are of great interest for future applications in the context of particle driven plasma wakefield acceleration experiments: self-modulation and transformer ratio studies. In both cases a high density electron beam is interacting with a plasma which has a density of about 1015 cm-3. ASTRA simulations were done to study the e-beam density along the existing PITZ beamline, especially at two different possible longitudinal positions of the planned plasma cell, in order to reach the particle density required for occurrence of self-modulation. The results of the beam dynamics studies are presented and discussed in this paper.