I am a postdoctoral researcher at the Center for mathematical Plasma Astrophysics (CmPA) at the Mathematics Department of KU Leuven (Leuven, Belgium). My research focuses on the kinetic behaviour of plasmas and the link between these microscopic scales with the plasma macroscopic evolution. My studies are based on the development and deployment of massively parallel kinetic algorithms. I use these powerful tools to investigate the physics of collisionless shocks and magnetic reconnection in laboratory and astrophysical plasmas. I am particularly intrigued by the recent prospect to probe astrophysical phenomena in the laboratory with the use of powerful laser beams. I am also interested in the possibility to employ these beams to develop compact plasma-based accelerators.
I obtained the BSc and MSc degrees in Energy and Energy and Nuclear Engineer in 2006 and 2009, respectively, from Politecnico di Torino (Turin, Italy). Part of the final Master project was developed at the Los Alamos National Laboratory (Los Alamos, NM), where I have been visiting student for eight months in 2009.
In 2010, I enrolled in a joint PhD program, which allowed me to pursue my research interests at Politecnico di Torino, under the guidance of Prof. G. Coppa, and at Instituto Superior Tecnico (IST) in the Group of Lasers and Plasmas (GoLP) led by Prof. L. O. Silva. My research focused on ion acceleration in laser-driven plasmas. I tackled some of the main questions on table-top ion accelerators from a theoretical perspective and from a numerical point of view. I performed massively parallel Particle-In-Cell (PIC) simulations and developed reduced gridless algorithms to focus on specific aspects of the acceleration dynamics. I obtained the PhD degrees in Energetics from Politecnico di Torino and Physics from IST in May 2014.
After the PhD, I continued to carry out my research on laser-driven collisionless shocks at GoLP until April 2016. In May 2016, I moved to KU Leuven, where I joined the group of Prof. G. Lapenta. Here, I contributed to the development of an innovative Energy Conserving PIC algorithm and I am currently applying it to study reconnection events in the solar corona and tangential discontinuities at the magnetopause, where highly energetic electrons are observed.
My research is devoted to understand the physics of collisionless plasma phenomena, such as shock waves and magnetic reconnection. In oder to gain deeper insight into these extremely non-linear processes, I develop and use kinetic codes. The outcomes of my studies are relevant for laser-driven plasmas and astrophysics.
Shock wave acceleration
Collisionless electrostatic shocks are strong nonlinear waves, whose formation is mediated solely by the plasma electrostatic field. Such waves can be excited in the laboratory by intense laser pulses interacting with for instance Hydrogen jets. Shocks generated in this way, can then travel through the plasma and reflect the ions at rest. Ions can then reach a velocity, which is about twice the shock speed. This mechanism, already demonstrated in the laboratory, allows for obtaining high energetic ions, with low energy spread and low divergence.
Coulomb explosion of clusters driven by intense laser pulses occurs whenever the laser is so intense to strip all the electrons from the target, leading to a pure ion plasmas. The Coulomb repulsive forces cause the explosion, which accelerates ions. A fascinating phenomenon during Coulomb explosion is the possible formation of shocks shells. A shock shell occurs when several ions with different velocities overtake each other. It naturally happens if the initial ion density profile is not uniform or when ions with different charge-to-mass ratio are simultaneously present. Interestingly, shock shells lead to quasi-monoenergetic ion spectra.
Magentic reconnection in the solar corona
Magnetic reconnection is the physical process leading to a sudden and rapid change of the magnetic field topology in magnetized plasmas. Investigating reconnection events occurring in the solar corona is particularly challenging due to the size of the system, which makes numerical modelling of the corona collisionless plasma particularly hard, and due to the current absence of observational instruments able to capture the microphysics of reconnection in the corona. The big challenge here is to understand how the small kinetic scales influence the macroscopic behaviour of the system.
The PIC technique models plasma as particles interacting self-consistently via the electromagnetic fields, which they produce. It works at the most fundamental microscopic level and it is the perfect tool to investigate the kinetic behaviour of plasmas. There are different families of PIC codes: explicit, semi-implicit and fully implicit. A wonderful example of explicit code is OSIRIS, a massively parallel fully relativistic PIC code. I am currently contributing to the development of an innovative energy conserving semi-implicit PIC algorithm called ECsim.
F. Fiuza, A. Stockem, E. Boella, R. Fonseca, L. Silva, D. Haberberger, S. Tochitsky, C. Gong, W. Mori and C. Joshi, Laser-driven shock acceleration of mono-energetic ion beams, Physical Review Letters, vol. 109, p. 215001, 2011.
F. Fiuza, A. Stockem, E. Boella, R. Fonseca, L. Silva, D. Haberberger, S. Tochitsky, W. Mori and C. Joshi, Ion acceleration from laser-driven electrostatic shocks, Physics of Plasmas, vol. 20, p. 056304, 2013.
A. Stockem, E. Boella, F. Fiuza and L. O. Silva, Relativistic generalization of formation and ion reflection condition in electrostatic shocks, Physical Review E, vol. 87, p. 043116, 2013.
A. d’Angola, E. Boella and G. Coppa, On the applicability of the collisionless kinetic theory to the study of nanoplasmas, Physics of Plasmas, vol. 21, p. 082116, 2014.
E. Boella, B. Peiretti Paradisi, A. d’Angola, L. Silva, and G. Coppa, Study on Coulomb explosions of ion mixtures, Journal of Plasma Physics, vol. 82, p. 905820110, 2016.
G. Lapenta, D. Gonzalez-Herrero and E. Boella, Multiple-scale kinetic simulations with the energy conserving semi-implicit particle in cell method, Journal of Plasma Physics, vol. 83, p. 705830205, 2017.
A. Stockem, F. Fiuza, E. Boella, R.A. Fonseca, L. O. Silva, C. Joshi, and W.B. Mori, Theoretical studies of collisionless shocks for laser-acceleration of ions, The proceedings of SPIE, vol. 8779, p. 87790B, 2013.
E. Boella, B. Peiretti Paradisi, A. d’Angola, G. Coppa and L. O. Silva, Dynamics of the Coulomb explosion of composite clusters, 41st EPS Conference on Plasma Physics, Berlin, June 2014.
A. d’Angola, E. Boella, G. Coppa, B. Peiretti Paradisi and R. Zaffina, N-body simulation of nanoplasmas, 41st EPS Conference on Plasma Physics, Berlin, June 2014.
A. Balzarini, R. Fonseca, J. Vieira, E. Boella and L. Silva, Initialization of charged particle beam in OSIRIS, 42nd EPS Conference on Plasma Physics, Lisbon, June 2015.
09.2016–01.2017 “Plasma Physics of the Sun” held at KU Leuven by Dr. E. Chane.
09.2016–01.2017 “Introduction to plasma dynamics” held at KU Leuven by Prof. G. Lapenta.
02.2017–06.2017 “Space weather” held at KU Leuven by Prof. G. Lapenta.
I have been involved in the co-supervision of the following Master projects:
B. Peiretti Paradisi, “Studio sulle esplosioni coulombiane di microplasmi” (Study on Coulomb explosions of micro-plasmas), Master Thesis, Politecnico di Torino, 2014 (final mark: 110/110 cum laude, now PhD candidate at Politecnico di Torino).
A. Balzarini, “Self-consistent particle beam EM field initialization for PIC simulations”, Master Thesis, Politecnico di Torino, 2015 (final mark: 110/110 cum laude, now at Cornaglia Group, Italy).
A. Micera, “Analysis of a new energy conserving particle in a cell method for plasma simulations”, Master Thesis, Politecnico di Torino, 2017 (final mark: 104/110, now PhD candidate at Royal Observatory Belgium).