Proton radiography in order to probe electromagnetic field in HED Plasmas

by Simon Bolanos (LULI - Ecole Polytechnique)

High-power laser facilities nowadays allow to accelerate protons to tens
of MeV in an extremely laminar fashion, i.e. originating from a small
source of only a few microns size, and over a duration of the order of a
picosecond. Such a proton beam is an unique tool to probe, with high
spatial resolution, fast-evolving electromagnetic fields embedded in
High-Energy-Density plasmas. Such a tool allows for the first time to
access in detail to the dynamics of many previously inaccessible phenomena
such as the growth of electromagnetic instabilities in plasmas, which have
usually strong implications in many astrophysical or space phenomena. We
will present an overview of the principle of proton deflectometry and some
of the techniques used to retrieve the E and B fields in the plasma. We
will discuss also the advantages and limitations of this diagnostic as
well as the way its data can be analysed. This will be illustrated by
practical cases of experiments where proton radiography has been used as
the main diagnostic.