Modeling of the nucleosynthesis of heavy elements induced by ultra-bright neutrons generated by means of PW laser
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Subject: Ultra-intense lasers offer, compared to what can be produced by conventional methods, extremely attractive prospects for generating fast neutrons (MeV) in a relatively inexpensive, extremely compact way, with furthermore controllable energy, and in a collimated way. With the next generation of lasers, such as the Apollon installation which will open on the Saclay plateau (https://apollonlaserfacility.cnrs.fr/
) with a high repetition rate (1 shot / min), and with high energy (~ 100 J), the possibility will open to generate ion and neutron currents via a spallation process, with peak fluxes (for neutrons up to 10^22 neutrons.cm ^-2.s ^-1; SN Chen et al., Matter Radiat. Extremes 4, 054402 (2019); https://doi.org/10.1063/1.5081666
). Not only is this type of peak flux out of reach of current and even future conventional accelerators, but because of the short duration of the source of neutrons (some 10s of ps) on a small surface (some 100s of microns), it will be reached with a relatively low absolute number of neutrons (10^10), which will make it generally safe. With such a source, it will be possible to tackle for the first time the experimental characterization of the so-called “r” (rapid) process of nucleosynthesis, which is supposed to generate, by simultaneous absorption of several neutrons, in the environment of either supernovae or of collision of neutron stars, all the heavy elements above Bismuth. This process is currently only theoretically postulated due to the neutron flux limit of current facilities, which have therefore not yet allowed it to be explored experimentally. The goal of the thesis will be to study in detail, in parallel with the realization of the experiments, and via numerical simulations, the best possible scenarios of experimental study of the "r" process. The work will use both so-called "particle-in-cell (PIC)" codes that resolve the laser-matter interaction at very high intensity, and nuclear physics codes (of the GEANT or FLUKA type) in order to simulate nuclear processes. The aim is to achieve the first characterization of nucleosynthesis of heavy elements. The candidate will focus on the chain of simulations but will participate closely in the experiments carried out in parallel. The project will be carried out within the general framework of the “GENESIS” project funded by the ERC (https://www.polytechnique.edu/en/content/julien-fuchs-recipient-2018-erc-advanced-grants-his-genesis
The PhD position will be based at LULI (https://portail.polytechnique.edu/luli/en
), on the campus of Ecole Polytechnique, Palaiseau (Paris area). Candidates are required to have a master degree, in physics or engineering. Salary is 1500-1600 € net/month. Applications are to be sent to Julien.email@example.com
, with a CV and letters of recommendation.