PAC2013 - List of Authors (Tsung, F.S.)

Paper	Title	Page
MOPAC10	Long Term Evolution of Plasma Wakefields	90
	A. A. Sahai, T.C. Katsouleas Duke ECE, Durham, North Carolina, USA W.B. Mori, F.S. Tsung UCLA, Los Angeles, California, USA
	Funding: NSF- PHY-0936278 We study the long-term evolution of plasma wakefields over multiple plasma-electron periods and few plasma-ion periods, much less than a recombination time. The evolution and relaxation of such a wakefield-perturbed plasma over these timescales has important implications on the upper limits of repetition-rates in plasma colliders. Intense fields in relativistic lasers (or intense beams) create highly non-linear space-charge wakefields by transferring energy to the plasma electrons. Synchronized charged-particle beams may be accelerated with acceleration/focusing gradients of tens of GeV/m. However, wakefields leave behind a plasma, not in equilibrium, with a relaxation time of multiple plasma-electron periods. Ion motion, over ion timescales, caused by energy transfer from the driven plasma-electrons to the plasma-ions can create interesting plasma states. Eventually, during this long-term evolution the dynamics of plasma de-coheres, thermalizing into random motion (2nd law of thermodynamics), dissipating energy away from the wakefields. Wakefield-drivers interacting with such a relativistically hot-plasma lead to plasma wakefields that differ from the wakefields in a cold-plasma. * J. Marques et al., Phys. Rev. Lett. 76 (1996) 10.1103/PhysRevLett.76.3566 L. Gorbunov et al., Phys. Plasma 10 (2003) 10.1063/1.1559011 A. Maksimchuk et al., Phys. Plasma 15 (2008) 10.1063/1.2856373

MOPAC47	Simulation of Laser Wakefield Acceleration in the Lorentz Boosted Frame with UPIC-EMMA	168
	P. Yu, W. An, V.K. Decyk, W.B. Mori, F.S. Tsung UCLA, Los Angeles, California, USA R.A. Fonseca, L.O. Silva, J. Vieira Instituto Superior Tecnico, Lisbon, Portugal W. Lu, X.L. Xu TUB, Beijing, People's Republic of China
	Funding: Work supported by the US DoE under grants DE-SC0008491, DE-FG02-92- ER40727, DE-SC0008316 and DE-SC0007970, and by National Science Foundation under grants PHY-0936266, PHY-0960344 and PHY-0934856. Simulation of laser wakefield accelerator (LWFA) in the Lorentz boosted frame, in which the laser and plasma spatial scales are comparable, can lead to computational time speed-ups to several orders of magnitude. In these simulation the relativistic drifting plasma inevitably induces a high frequency numerical instability. To reduce this numerical instability, we developed an EM-PIC code, UPIC-EMMA, based on the components of UCLA PIC framework (UPIC) which uses a spectral solver to advance the electromagnetic field in the Fourier space. With a low pass or "ring" filter implemented in the spectral solver, the numerical instability can be eliminated. In this paper we describe the new code, UPIC-EMMA, and present results from the code of LWFA simulation in the Lorentz boosted frame. These include the modeling cases where there are no self-trapped electrons, and modeling the self-trapped regime. Detailed comparison among Lorentz boosted frame results and lab frame results obtained from OSIRIS are given. We have used UPIC-EMMA to study LWFA in the self-guided regime to 100 GeV and good agreement was found with analytical scaling.

Paper

Title

Page

Long Term Evolution of Plasma Wakefields

90

A. A. Sahai, T.C. Katsouleas
Duke ECE, Durham, North Carolina, USA
W.B. Mori, F.S. Tsung
UCLA, Los Angeles, California, USA

Funding: NSF- PHY-0936278
We study the long-term evolution of plasma wakefields over multiple plasma-electron periods and few plasma-ion periods, much less than a recombination time. The evolution and relaxation of such a wakefield-perturbed plasma over these timescales has important implications on the upper limits of repetition-rates in plasma colliders. Intense fields in relativistic lasers (or intense beams) create highly non-linear space-charge wakefields by transferring energy to the plasma electrons. Synchronized charged-particle beams may be accelerated with acceleration/focusing gradients of tens of GeV/m. However, wakefields leave behind a plasma, not in equilibrium, with a relaxation time of multiple plasma-electron periods. Ion motion, over ion timescales, caused by energy transfer from the driven plasma-electrons to the plasma-ions can create interesting plasma states. Eventually, during this long-term evolution the dynamics of plasma de-coheres, thermalizing into random motion (2nd law of thermodynamics), dissipating energy away from the wakefields. Wakefield-drivers interacting with such a relativistically hot-plasma lead to plasma wakefields that differ from the wakefields in a cold-plasma.
* J. Marques et al., Phys. Rev. Lett. 76 (1996) 10.1103/PhysRevLett.76.3566
** L. Gorbunov et al., Phys. Plasma 10 (2003) 10.1063/1.1559011** A. Maksimchuk et al., Phys. Plasma 15 (2008) 10.1063/1.2856373

MOPAC47

Simulation of Laser Wakefield Acceleration in the Lorentz Boosted Frame with UPIC-EMMA

168

P. Yu, W. An, V.K. Decyk, W.B. Mori, F.S. Tsung
UCLA, Los Angeles, California, USA
R.A. Fonseca, L.O. Silva, J. Vieira
Instituto Superior Tecnico, Lisbon, Portugal
W. Lu, X.L. Xu
TUB, Beijing, People's Republic of China

Funding: Work supported by the US DoE under grants DE-SC0008491, DE-FG02-92- ER40727, DE-SC0008316 and DE-SC0007970, and by National Science Foundation under grants PHY-0936266, PHY-0960344 and PHY-0934856.
Simulation of laser wakefield accelerator (LWFA) in the Lorentz boosted frame, in which the laser and plasma spatial scales are comparable, can lead to computational time speed-ups to several orders of magnitude. In these simulation the relativistic drifting plasma inevitably induces a high frequency numerical instability. To reduce this numerical instability, we developed an EM-PIC code, UPIC-EMMA, based on the components of UCLA PIC framework (UPIC) which uses a spectral solver to advance the electromagnetic field in the Fourier space. With a low pass or "ring" filter implemented in the spectral solver, the numerical instability can be eliminated. In this paper we describe the new code, UPIC-EMMA, and present results from the code of LWFA simulation in the Lorentz boosted frame. These include the modeling cases where there are no self-trapped electrons, and modeling the self-trapped regime. Detailed comparison among Lorentz boosted frame results and lab frame results obtained from OSIRIS are given. We have used UPIC-EMMA to study LWFA in the self-guided regime to 100 GeV and good agreement was found with analytical scaling.