Description du sujet de thèse

The PhD science project aims to measure several self-diffusion properties within a strongly correlated non-neutral plasma simulated by a laser-cooled ion cloud in a linear radio-frequency trap.

The experimental protocol to design will take advantage of the engineering of the different black states built by laser-atom coupling, to control the relevant time scales of the internal state dynamics and of the pressure force imposed by Doppler laser cooling. These measurements are very important to benchmark potential models and test plasma theories out of the conventional plasma regimes.

The first part of this project will be to identify the experimental parameters that will give access relevant measurements of the diffusion coefficients. Then, the compatibility of these parameters with Doppler laser cooling of the large ion cloud will have to be validated before the measurement period can start. It will be a real asset to carry out these measurements within the liquid and crystal phases of the ion cloud as the diffusion at the microscopic scale is expected to be different.

To perform these measurements, the candidate will use and maintain an already existing experimental setup, involving diodes and solid-state lasers and a linear radio-frequency trap. Typical cold ion laser techniques, such as photoionization and Doppler cooling, will also rapidly be part of the candidate experimental routine. The engineering of a three-photon black state and the frequency stabilization of all involved lasers is reached through an optical frequency comb, stabilized by a local ultra-stable laser and absolute frequency measurements are allowed through our connection to the REFIMEVE network.

The main experimental data will come from a detailed analysis of the cloud pictures, from which information concerning the self-diffusion within the cloud can be extracted, thanks to the support of a model that is presently under construction and validation, in collaboration with statistical physics theoreticians. We have also built a molecular dynamics simulation of the experiment that can be used to complement the experimental studies and the analytic model to reach an insight at the microscopic level. This code will be a relevant tool available to guide the future experiments toward a relevant set of parameters.

The acquired skills concern ion trapping in radio-frequency traps, high resolution frequency control of laser systems, coherent and non-coherent atoms-lasers interactions, image processing, and modeling for diffusion in a charged finite system.


Publications related to the project:
• C. Champenois, Tutorial: About the dynamics and thermodynamics of trapped ions, J. Phys. B: At. Mol. Opt. Phys. 42 154002 (2009)
• T. S. Strickler, et al. Experimental Measurement of Self-Diffusion in a Strongly Coupled Plasma PRX 6, 021021 (2016)
• B. Scheiner and Scott D. Baalrud, Testing thermal conductivity models with equilibrium molecular dynamics simulations of the one-component plasma, Phys. Rev. E 100, 043206 (2019)
• S. Balruud and J. Daligault, Mean force kinetic theory: A convergent kinetic theory for weakly and strongly coupled plasmas. Phys. Plasmas, 082106 (2019)
• M. Marciante, C. Champenois, A. Calisti, J. Pedregosa-Guttierez and M. Knoop, Ion dynamics in a linear radio-frequency trap with a single cooling laser, Phys. Rev. A. 82 (2010) 033406.
• Poindron, J. Pedregosa-Gutierrez, C. Jouvet, M. Knoop and C. Champenois, Non-destructive detection of large molecules without mass limitation J. Chem. Phys. 154, 184203 (2021)
• M. Collombon, et al. Experimental Demonstration of Three-Photon Coherent Population Trapping in an Ion Cloud, Phys. Rev. Applied 12, 034035 (2019) , hal-02064988

Contexte de travail

The activity will take place on the university site of Saint-Jérôme in Marseille. The PIIM laboratory is classified in a restricted area (ZRR) which requires the attribution of a specific access authorization.

The PIIM laboratory brings together physicists and physical chemists who study dilute media - such as gases, plasmas and beams of ions, atoms and/or molecules – as well as their interactions with matter and light. The person recruited will work in the CIML (Confinement d'Ions et Manipulation Laser) research team, which has a strong expertise in radio-frequency ion trapping and optical frequency metrology.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

• Risk related to ionizing radiation,
• Laser risk,
• Work on screens.

Informations complémentaires

The candidate (M/W) must have a master's degree in Physics and a good knowledge of atomic and optical physics. Interest in experimental physics is essential. Coding and data processing skills will be highly appreciated.

Ability to work in a team, autonomy, and initiative are also required.