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PhD subjects

Dernière mise à jour : 18-01-2018

3 sujets IRAMIS

«««

• Radiation-matter interactions

 

Attosecond XUV pulses carrying an angular momentum: synthesis and novel spectroscopies

SL-DRF-18-0221

Research field : Radiation-matter interactions
Location :

Service Laboratoire Interactions, Dynamique et Lasers (LIDyL)

Attophysique (ATTO)

Saclay

Contact :

Thierry RUCHON

Starting date : 01-09-2018

Contact :

Thierry RUCHON

CEA - DRF/IRAMIS/LIDyL/ATTO

0169087010

Thesis supervisor :

Thierry RUCHON

CEA - DRF/IRAMIS/LIDyL/ATTO

0169087010

Personal web page : http://iramis.cea.fr/LIDYL/Pisp/thierry.ruchon/

Laboratory link : http://iramis.cea.fr/LIDYL/ATTO/

Light in the extreme ultraviolet (XUV) is a universal probe of mater, may it be in diluted or condensed phase: photons associated with this spectral range carry energy of 10 to 100 eV, sufficient to directly ionize atoms, molecules or solids. Large scale instruments such as synchrotrons or the lately developed free electron lasers (FEL) work in this spectral range and are used to both study fundamental light matter interaction and develop diagnosis tools. However these instruments do not offer the temporal resolution require to study light matter interactions at their ultimate timescales, which is in the attosecond range (1as = 10^-18s). An alternative is offered by the recent development of XUV sources based on high order harmonic generation (HHG). They are based on the extremely nonlinear interaction of a femtosecond intense laser beam with a gas target. Our laboratory has pioneered the development, control and design of these sources providing XUV attosecond pulses.



During this PhD project, we will develop specific setups to allow these attosecond pulse to carry angular momenta, may it be spin or orbital angular momenta. This will open new applications roads through the observations of currently ignored spectroscopic signatures. On the one hand, the fundamental aspects of the coupling of spin and orbital angular momentum of light in the highly nonlinear regime will be investigated, and on the other hand, we will tack attosecond novel spectroscopies, may it be in diluted or condensed phase. In particular, we will chase helical dichroism, which manifest as different absorptions of beams carrying opposite orbital angular moments. These effects are largely ignored to date.



The student will acquire practical knowledge about lasers, in particular femtosecond lasers, and hands on spectrometric techniques of charged particles. He/she will also study strong field physical processes which form the basis for high harmonic generation. He/she will become an expert in attosecond physics. The acquisition of analysis skills, computer controlled experiments skills will be encouraged although not required.

Full subject available at http://iramis.cea.fr/LIDYL/Pisp/thierry.ruchon/.

Fast and innovative understanding of ageing processes in lithium-ion batteries by radiolysis

SL-DRF-18-0424

Research field : Radiation-matter interactions
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l'Energie (NIMBE)

Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire (LIONS)

Saclay

Contact :

Sophie LE CAER

Starting date : 01-09-2018

Contact :

Sophie LE CAER

CNRS - DRF/IRAMIS/NIMBE/LIONS

01 69 08 15 58

Thesis supervisor :

Sophie LE CAER

CNRS - DRF/IRAMIS/NIMBE/LIONS

01 69 08 15 58

Personal web page : iramis.cea.fr/Pisp/sophie.le-caer

Laboratory link : http://iramis.cea.fr/nimbe/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=50

Ageing and safety issues are a critical challenge for lithium-ion batteries. Recently we have demonstrated for the first time that radiolysis (i.e. the chemical reactivity induced by the interaction between ionizing radiation and matter) is a powerful tool for a short-time (minutes-days) identification of the by-products arising from the degradation of the electrolyte of a lithium-ion battery, after several weeks or months of cycling.



The aim of the present PhD thesis is to extend the radiolysis approach to:

* screen electrolytes and combinations of electrolyte and active materials to identify the most robust ones. Reaction mechanisms induced by ionizing radiation will be studied in details for the most promising electrolytes identified;

* study carefully the interfacial processes (electrode/electrolyte) with negative and positive électrodes for the most interesting systems previously identified.



A global and detailed picture of reaction mechanims at stake in lithium-ion batteries will thus be provided. Moreover, the systems; which are the most robust towards ionizing radiation and thus to electrolysis, will be identified and carefully studied.

Plasma mirrors on-chip : “towards extreme intensity light sources and table-top particle accelerators”

SL-DRF-18-0432

Research field : Radiation-matter interactions
Location :

Service Laboratoire Interactions, Dynamique et Lasers (LIDyL)

Physique à Haute Intensité (PHI)

Saclay

Contact :

Henri VINCENTI

Guy BONNAUD

Starting date : 01-10-2018

Contact :

Henri VINCENTI

CEA - DRF/IRAMIS/LIDyL/PHI

0169080376

Thesis supervisor :

Guy BONNAUD

CEA - DRF/IRAMIS/LIDyL/PHI

0169088140

Personal web page : http://iramis.cea.fr/Pisp/henri.vincenti/

Laboratory link : http://iramis.cea.fr/LIDYL/PHI/

More : https://www.picsar.net

With the advent of PetaWatt (PW) class lasers capable of achieving light intensities of 10^22W.cm-2 at which matter turns into a plasma, Ultra-High Intensity (UHI) physics now aims at solving two major challenges: can we produce high-charge compact particle accelerators with high-beam quality that will be essential to push forward the horizons of high energy science? Can we reach extreme light intensities approaching the Schwinger limit 10^29W.cm-2, beyond which light self-focuses in vacuum and electron-positrons pairs are produced? Solving these major questions with the current generation of high-power lasers will require conceptual breakthroughs that will be developed during this PhD.



In particular, the goal of this PhD proposal is to demonstrate that so-called ‘relativistic plasma mirrors’, produced when a high-power laser hits a solid target, can provide simple and elegant paths to solve these two challenges.  Upon reflection on a plasma mirror surface, lasers can produce high-charge relativistic electron bunches and bright short-wavelength attosecond harmonic beams. Could we use plasma mirrors to tightly focus harmonic beams and reach extreme light intensities, potentially approaching the Schwinger limit? Could we employ plasma mirrors as high-charge electron injectors in a PW laser capable of delivering accelerating gradients of 100TV.m-1, or in a laser wakefield accelerator, to build ultra-compact particle accelerators?



The mission of the PhD candidate will be to answer these two interrogations ‘on-chip’ using massively parallel simulations on the largest supercomputers in the world. To this end, the successful candidate will make use of our recent transformative developments in ‘first principles’ Particle-In-Cell (PIC) simulations of UHI laser-plasma interactions that enabled the 3D modelling of plasma mirror sources with high-fidelity on current petascale and future exascale supercomputers. These developments were recently implemented, validated and tested in our code PICSAR (https://www.picsar.net). Armed with PICSAR, the candidate will model novel schemes employing plasma mirrors to address the two UHI challenges introduced above.

 

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