Speaker
Anton Helm
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.2034.pdf
Parametric studies using reduced 3d modeling on plasma scale lengths
A. Helm1 , J. Vieira1 , R.A. Fonseca1,2 , L.O. Silva1 , P. Muggli3
1 GoLP/IPFN Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
2 Instituto Universitário de Lisboa (ISCTE-IUL), Lisboa, Portugal
3 Max Planck Institute for Physics, Munich, Germany
Current modeling for plasma-based accelerators is often performed with the help of particle
in cell (PIC) codes. While accurate, these codes require following the smallest spatial/temporal
scales, and as a result, are computationally expensive. Reduced models, such as the ponderomo-
tive guiding center solver (PGC) [1, 2] overcome this limitation and provide speedups in order
of ∼(λ0 /λ p )2 , where λ0 is the laser wavelength and λ p the plasma skin depth. The speed up
is a result of a reduced description of the laser: instead of resolving the fast laser wavelength,
PGC captures the evolution of the laser envelope instead. The PGC is thus ideal to explore the
effects of ionization seeding for the AWAKE project [3, 4]. AWAKE relies on the self-modu-
lation instability (SMI) to bunch an initially long proton bunch into bunchlets smaller than the
plasma wavelength. An ionizing laser co-propagates with the laser, creating a sharp ionization
front that seeds the SMI. These simulations are ideal for PGC, because the computational gains,
is in excess of (λ0 /λ p )2 > 106 . .We performed parametric studies using the massively parallel,
fully relativistic PIC code OSIRIS [5] for the self modulation instability (SMI) as part of the
main mechanism for the AWAKE project. The influence of the neutral gas density on the SMI
and the injected electrons is discussed. Furthermore, studies on different injection schemes in
the plasma scale regime, such as downramp injection and ionization injection is discussed and
compared with full 3d PIC and Quasi-3D [6] simulations.
This work was partially supported by Fundação para a Ciência e Tecnologia (FCT), Portugal,
through grant no. PTDC/FIS-PLA/2940/2014 and PD/BD/105882/2014.
References
[1] D. F. Gordon et al., IEEE Trans. Plasma Sci., 28(4), 1135 (2000)
[2] B. M. Cowan et al., Journal Comp. Physics, 230(1), 61 (2011)
[3] A. Caldwell et al., Nat. Phys. 5, 363 (2009)
[4] N. Kumar et al., PRL 104, 255003 (2010)
[5] R. A. Fonseca et al., Lect. Notes Comp. Sci., 2331, 343 (2002)
[6] A. Davidson et. al., Journal Comp. Physics, 281, 1063 (2015)
