Post-doctoral (M/F) researcher in characterization of innovative carbon-based nanomaterials

A fully-funded post-doctoral position (2 years), as part of the i-DEMO regionalized project (France 2030) M.A.G.I.C. (Matériaux Avancés pour l’Innovation en Graphène et Cristallographie), is available until April 1, 2025 in the “Physique des Interactions Ioniques et Moléculaires” (PIIM) laboratory of Aix-Marseille Université, CNRS (France).

As part of the M.A.G.I.C. project, we are looking for an experimental postdoctoral researcher to work on the development and characterization of innovative carbon-based nanomaterials, such as Ginestium©, multilayer rhombohedral graphene and other relevant systems. Ginestium© could be a revolutionary nanostructured carbon material developed by EffiBLUE (https://effiblue.com). Multilayer rhombohedral graphene and some multilayer twisted graphene are known to be superconductors at temperatures close to 1K. Manipulating the structural properties of carbon-based materials, such as sp2/sp3 ratio and stacking configurations, enables fine-tuning of their physical characteristics, including electronic conductivity, optical response and mechanical strength. These tunable materials have great potential for applications in the electronics, telecommunications and energy sectors.

This complete job offer is available here. Applications should be sent via the candidate space on the CNRS website.

High Performance Computing: research engineer

The Institut de Recherche sur la Fusion par Confinement Magnétique (IRFM) is part of the Fundamental Research Department (DRF) of the CEA. For over 50 years, its role has been to conduct research on a new energy source: magnetic confinement fusion, in collaboration with the European Fusion program. The activities of the IRFM are structured around three axes of research and development:

– Contributing to the realization of the ITER project and those of the Expanded Approach (mainly the JT-60SA tokamak),

– Preparing the scientific operation of ITER.

The IRFM is associated to the PIIM laboratory (Aix Marseille University) in the present research program. The person will be hired by AMIDEX, Aix Marseille University and will mostly work in the GC3I group at IRFM CEA.

The activities of the GC3I are organized into three main themes:

– Administration of local IT infrastructure (network, service servers, computing servers, and databases),

– Management and monitoring of IT projects (application and system development),

– HPC/AI (exascale code optimization, development of AI models dedicated to fusion).

The group consists of about ten people who collaborate on these closely related themes. The HPC activities of the group are mainly focused on providing high-level support to first-principles code developers (Gysela, JOREK, Soledge3X) regarding development, code porting to new architectures, and code optimization, with the aim of efficiently performing simulations on exascale supercomputers.

You will be in charge of redesigning the parallelisation of a code [Fubiani G 2017 New J. Phys. 19 015002] which simulates the main physical mechanisms of low temperature magnetized plasmas dedicated to negative ion sources of neutral beam heating systems of fusion reactors. The objective of this numerical model is to obtain a qualitative and quantitative understanding of plasma transport and plasma chemistry (hydrogen or deuterium) in the magnetic confinement of the source, the conversion of the plasma dominated by the positive ions into an electronegative plasma leading to the production of negative ions (H- or D-), the in-depth study of the plasma-beam interface (magnetic plasma sheath) which requires a high grid resolution, primary cause of ionic optical aberrations downstream in the acceleration channel

The code is based on the PIC approach, combining a particle representation of the plasma and a 3D Poisson solver in Cartesian geometry. It is written in Fortran 90 and currently only parallelised in OpenMP. An iterative method simulates the electric potential and densities of each species composing the plasma (electrons and ions) for each time step increment. These simulations require the use of supercomputers and it is therefore essential to upgrade the parallelisation of the code so that it can run on massively parallel scalar and/or accelerated architectures.

The actions associated with this position over the duration of the position are:

– establishing the MPI+OpenMP parallelization strategy,

– validation of the results,

– study of the code performance on massively parallel architectures (strong scaling, weak scaling, …),

– optimisation the code for efficient use of supercomputers,

– development of post-processing and monitoring tools,

– extension the code to GPU using OpenMP offloading (OpenMP target).

You have a degree equivalent to at least a Master’s degree or equivalent (BAC+5) in scientific computing and some experience in development for a parallel simulation code. You have skills and experience with Fortran and Python as well as parallelisation using MPI and OpenMP. Knowledge of GPU programming and/or plasma physics is a plus.

You will work in an international research environment in close collaboration with experts in the fields of fusion plasma physics, high-performance computing, and artificial intelligence. You will be required to present your work within the institute and potentially at conferences in your field of expertise.

You will benefit from 100 days of compensated telecommuting per year.

 

Where to apply

E-mail

Requirements

Research Field
Computer science » Programming
Education Level
Master Degree or equivalent
Skills/Qualifications

You have a degree equivalent to at least a Master’s degree or equivalent (BAC+5) in scientific computing and some experience (1-2 years) in development for a parallel simulation code. You have skills and experience with Fortran and Python as well as parallelisation using MPI and OpenMP. Knowledge of GPU programming and/or plasma physics is a plus.

Required skills: Fortran, python, shell, MPI, OpenMP, OpenACC. Unix system

Euraxess: https://euraxess.ec.europa.eu/jobs/231498

Postdoc position – Physics – experimentation – 2024/2025 – H2M/CM/1

Interaction of helium plasmas with tungsten surfaces in the context of controlled thermonuclear fusion

The subject of this research is within the framework of nuclear fusion development. ITER, currently under construction at Cadarache, will be the largest fusion reactor (tokamak). ITER’s main objective is to demonstrate the efficiency of plasma combustion through the fusion reactions between two isotopes of hydrogen, deuterium and tritium, producing a helium and a neutron. In tokamaks, despite the confinement of the plasma by intense magnetic fields, some ions escape this confinement and interact with the materials in contact with the plasma. One of the most important challenges for the success of nuclear fusion is the development of materials that can tolerate the following extreme conditions: high thermal load (20 MW to 100 MW.m-2) and high particle flux of H and He isotopes (1024 m-2.s-1) with a range of impact energies from eV to keV.

Tungsten (W) is currently considered the most promising material, particularly for the divertor component, which plays a key role in extracting excess heat and particles. Its appeal is mainly due to its low sputtering efficiency, high melting point (3410°C), high thermal conductivity and good thermomechanical properties. However, despite these advantages, there are serious concerns about helium-tungsten interaction in a fusion plasma environment. It has been shown that interaction with He significantly affects the surface and subsurface, with the formation of dislocation loops, nanobubbles or W nanotendrils (known as fuzz). These structures, particularly nanobubbles, can modify the thermomechanical properties and increase the retention of tritium in the material, two major concerns for next-generation reactors. In addition, the accumulation of helium in the bubbles, the destructuring of the surface and a possible sudden release of helium and W atoms by the bursting of the bubbles, modifying the wall and the plasma, generate new, unexplored plasma-wall interactions whose consequences for the operation of ITER must be anticipated.

The aim of the proposed experimental work is to study the properties of tungsten under He irradiation and, more specifically, to quantify the Helium trapped in the bubbles formed, which are a few nanometres in diameter. The first stages in the formation of He bubbles in the W, their dynamics and evolution under the effect of thermal cycles will be analysed at micro- and nanometric scales. To this end, a study including preparation and pre-characterisation of the W sample, exposure to a He plasma and post-exposure characterisation of the distribution of bubbles and their He content will be carried out at the PIIM laboratory. Experimental techniques dedicated to the study of surfaces from the H2M team (C. Martin) such as electron microscopy, electron diffraction, atomic force microscopy, optical measurements as well as plasma implantation experiments with in-situ diagnostics from the PS team (G. Cartry) will be implemented by the candidate.

A large number of experimental parameters, from the characteristics of the sample (quality of the W, crystalline orientation, defects, etc.) to the He plasma exposure conditions (ionic energy, flux, fluence, surface temperature, etc.) are influencing He bubble formation and make the interpretation of the basic mechanisms of microstructure evolution complex.  After exposure to He, the He bubbles formed are generally pressurised (several GPa) and, according to Laplace’s law, the He content (atomic density) should decrease in inverse proportion to the radius of the bubble. To date, this has never been confirmed for the He-W system. To meet this challenge, the quantitative determination of the density of He atoms inside a bubble and its comparison with the shape (spherical or facetted), size and formation conditions will be carried out using the STEM-electron energy loss spectroscopy (-EELS) technique. Measurement of the 1s2 → 1s2p transition of the trapped Helium and of the plasmon of the W on the same spectrum will enable the He-W system to be analysed on an atomic scale and to develop our understanding of the trapping of He and the modification of W.

The candidate should have a taste for experiments and data processing (images, spectra). He/she should also have knowledge of nuclear fusion, and/or solid state physics, and/or plasma