Missions

The interiors of the ice giants Uranus and Neptune are largely composed of the light elements hydrogen, helium, carbon, nitrogen and oxygen (CHNO) at extreme pressures of several million atmospheres and temperatures of several thousand kelvins. These environments presumably allow the formation of unfamiliar structures, such as superionic states of water and ammonia, and exotic chemistry, e.g., the dissociation of hydrocarbons into diamond and metallic hydrogen. These processes are highly complex and, so far, cannot be modelled reliably with existing theory and simulation methods. At the same time, they are thought to significantly shape the internal structure and evolution of Uranus and Neptune and may be key to explain the unusual magnetic fields observed for both planets, and to elucidate their internal heat balance. Moreover, planets of similar size and probably composition, in particular so-called “sub-Neptunes”, are found to be highly abundant outside our Solar System. Thus, a better understanding of matter at conditions comparable to the interior of ice giants is required for both better models of our Solar System and a reliable classification of exoplanets from telescope data of mass and radius.
In the last years, the PHYHDEL group at the LULI laboratory at the Ecole Polytechnique in France started a scientific program focused on the characterization of the properties of CHNO mixtures under high pressure and temperature conditions obtained with laser-generated shock compression. A DFG-ANR collaborative project, PROPICE, between PHYHDEL and the German team headed by Prof. D. Kraus, has lately been granted to pursue this research with focus on in situ microscopic probing. This post-doctoral position fits into this context.
In this project the candidate will actively participate at experimental campaigns on large facilities, including high energy lasers and XFEL. She/He will also be in charge of the target preparations and characterization. On the basis on the first experimental results she/he will propose improvements and optimization on the target design in order to achieve the finest data set. The candidate will also be in charge of the data analysis, both on optical and X-ray diagnostics. He/She will work in tight connections with theoretician to discuss the results' interpretation. She/He will be disseminate the obtained results in international conferences and peer-reviewed papers.

Activités

In this project our team has already been granted experiments on X-Ray Free Electron Lasers (XFEL) facilities in Germany (EuropeanXFEL) and USA (LCLS).
-She/He will participate and lead such campaigns. In particular, the work will focus on water-ammonia compounds with different concentrations and various CHNO mixtures.
-She/He will implement x-ray diffraction, X-ray Thomson scattering and Small Angle Scattering diagnostics.
-She/He will participate at the conception and realization of pertinent samples. This will comprise liquid samples as well as pre-compressed targets in diamond anvil cells.
-She/He will take in charge the data analysis.
-She/He conceive, prepare and submit proposal for future experiments on LULI 2000 and XFEL facilities.

Compétences

- Experience in High-pressure field
- Basic knowledge on Physics of Materials and Physics of Plasmas
- Experience on team-work on large facilities (lasers, synchrotrons, XFEL, ..)
- Knowledge on X-ray diffraction and crystallography
- Autonomy,
- Organizational skills
- Ability to report
- Communication and argumentation skills, synthesis and critical analysis.
- Ability to learn on your own and to develop skills.
- Ability to adapt and be creative
- - Languages: English (written, oral)

Contexte de travail

The position will be based at the LULI laboratory, on the Ecole Polytechnique campus near Paris, but the chosen candidate will work in close collaboration with the German partner. He/She will profit from a fruitful environment benefiting from interactions and exchanges within both the French and German teams. Experiments will also be intermixed with discussion sessions on collected data with relevant experts from the ab-initio and planetary model communities.

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

The experiments will be done on different facilities, comprising LULI 2000 and XFEL where planning is imposed and fixed by the facility. The candidate should be flexible with scheduling and travelling.