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Full Scale Modelling of the Proton Driven Plasma Wakefield Accelerator

Principal Investigator: Jorge Vieira, Instituto Superior Técnico, Lisboa (Portugal)
HPC Platform: SuperMUC of LRZ

Plasmas can sustain electric fields that can be orders of magnitude higher than material breakdown thresholds. Thus, even in the presence of extremely high electric fields, a plasma in an equilibrium will simply readjust in order to reach a new equilibrium state, without loosing any of its properties. This unique feature has been exploited towards the development of novel, more compact, plasma-based accelerators. Although there is still much room for improvement, plasma accelerators have the potential to either improve or to assist conventional particle acceleration techniques towards the construction of increasingly powerful accelerator devices and associated light sources.

There are many university scale laboratories where plasma based acceleration experiments are routinely performed, and several experiments are being planned in national and international facilities around the world. One of the most exciting of such projects is the proton driven plasma wakefield accelerator currently under preparation at CERN. In this project, a long proton beam from the Super-Proton Synchrotron will excite large amplitude plasma waves that will be used to accelerate electrons to high energies. A large collaboration has been set up, called the AWAKE collaboration (AWAKE).

One of the challenges for AWAKE is to stabilise proton beam propagation over very long distances. With the unique computational power of high performance computing (HPC) system SuperMUC, researchers of the Group for Lasers and Plasmas (GoLP) at the Institute for Plasmas and Nuclear Fusion of Instituto Superior Técnico in Lisboa (Portugal), of the Max Plank Institute for Physics in Munich (Germany), and of the University of California in Los Angeles (USA) have performed three-dimensional simulations of AWAKE relevant scenarios. Their numerical findings, obtained using OSIRIS, a massively parallel fully relativistic particle-in-cell code, provided a set of conditions for which the long proton bunches could propagate over arbitrarily long distances [1]. The work also establishes a set of conditions for which the beam propagation becomes unstable. As a result, the physicists defined sets of parameters that can be used to stabilise the propagation, to study particle acceleration, or explore new physics associated with unstable beam modes (Figure 1).

Full Scale Modelling of the Proton Driven Plasma Wakefield AcceleratorFig. 01: Three dimensional simulation result illustrating the propagation of a long particle beam (yellow-green isosurfaces) in a plasma. The plasma density perturbations grow from the head of the beam to the tail of the beam (mesh). Projections of the particle beam density are shown in blue. The arrow indicates the propagation direction of the long beam.
Copyright: Instituto Superior Técnico, Lisboa (Portugal)

In addition to particle acceleration, similar setups could also be exploited towards understanding fascinating astrophysical mysteries. The scientists have then performed three-dimensional simulations that can be related with the origin and amplification of galactic or extra galactic magnetic fields. In collaboration with an experimental team at Laboratoire d'Optique Appliquée (Paris, France), they have then found a new mechanism for the generation of large-scale, persistent magnetic fields that could occur in astrophysical scenarios [2] (Figure 2). The three-dimensional simulations used a laser pulse driver, but similar findings could also be found by using proton beam drivers. In addition, it was also shown that electron-positron particle bunches from laser-driven plasma accelerators could greatly amplify ambient magnetic fields (Figure 3). Similar physics could also occur during the propagation of a long proton bunch in conditions close to the AWAKE experiment [3].

Full Scale Modelling of the Proton Driven Plasma Wakefield AcceleratorFig. 02: Illustration of the magnetic fields generated around a plasma due to relativistic particles crossing the boundary between the plasma and the neutral gas. The magnetic fields are shown in blue/red. This is a very large-scale simulation, including ionisation and where the entire > 1 mm long gas jet was placed in the simulation box.
Copyright: Instituto Superior Técnico, Lisboa (Portugal)

Full Scale Modelling of the Proton Driven Plasma Wakefield AcceleratorFig. 03: Illustration of the current filamentation instability that can occur when a neutral electron-positron fireball beam propagates in a plasma. The properties of the beam are similar to those that can be obtained in current plasma based acceleration experiments.
Copyright: Instituto Superior Técnico, Lisboa (Portugal)

References:

[1] J. Vieira, W. B. Mori, P. Muggli, Phys. Rev. Lett. 112, 205001 (2014).
[2] A. Flacco, J. Vieira, A. Lifshitz, F. Sylla, S. Kahaly, M. Veltcheva, L. O. Silva, V. Malka, Nature Physics 11, 409 (2015).
[3] G. Sarri, K. Poder, J. M. Cole, W. Schumaker, A. Di Piazza, B. Reville, T. Dzelzainis, D. Doria, L. A. Gizzi, G. Grittani, S. Kar, C. H. Keitel, K. Krushelnick, S. Kuschel, S. P. D. Mangles, Z. Najmudin, N. Shukla, L. O. Silva, D. Symes, A. G. R. Thomas, M. Vargas, J. Vieira, M. Zepf, Nature Communications 6, 6747 (2015).

Research team:

L.D. Amorim, J. Vieira (PI project), R.A. Fonseca, L.O. Silva (IST)
Website plasma simulation team: http://epp.ist.utl.pt

P. Muggli, A. Caldwell (MPP)
Website: https://www.mpp.mpg.de/~muggli/AWAKEatMPP.html

Acknowledgments:

The project was made possible through the access to the HPC system SuperMUC of Leibniz Supercomputing Centre in Garching near Munich (Germany). Further credits go to the Alexander von Humboldt Foundation (Germany) and to the European Research Council (ERC-2010-AdG Grant No. 267841)

Scientific Contact:

Jorge Vieira
GoLP - Group for Lasers and Plasmas
Institute for Plasmas and Nuclear Fusion
Instituto Superior Técnico
Avenida Rovisco Pais 1, P-1049-001 Lisboa/Portugal
e-mail: jorge.vieira [at] ist.utl.pt
http://epp.ist.utl.pt/jorgevieira

February 2016