Nos tutelles



Accueil > PIIM > Positions > PhD opportunities > PhD opportunities 2017

Line shape calculations in dense plasmas submitted to a strong magnetic field.

publié le

Thesis advisor : Sandrine FERRI
Email and address : sandrine.ferri@univ-­‐, Service 232 Laboratoire PIIM, UMR 7345
Avenue Escadrille Normandie-­Niemen, 13397 Marseille Cedex 20
Tel : +33 491288623
Co-­‐advisor :

Subject description :
Highly magnetic atomic systems have been a great deal of interest in recent years. They occur in the high-­‐energy-­‐density (HED) environnements characteristic of intense laser-­‐matter interactions (Inertial Fusion Confinement, etc.) and astrophysical compact objects (white dwarf atmospheres, neutron stars). Kilotesla magnetic fields can be generated in plasmas where the temperature can reach several hundreds of eV and where densities are up to 1021cm-­3. In such extreme conditions, the atoms are partially ionized resulting in a mixture of ions, electrons and neutrals. The emitted radiation from these species is closely related to the atomic physics and the plasma environnement. As the photon energy of the emitted lines, their intensity and their broadening are related to physical quantities of the plasma (electron density, temperature, ion velocity, charge states, etc.), the line emission of the atomic species serves as an important tool to diagnose HED systems. In that context, it is of interest to develop line shape calculations of multi-­‐charged ions in dense plasmas submitted to a large external magnetic field.
The presence of magnetic fields increases the complexity of the calculations. A magnetic field has three essential effects on spectral lines : -­‐ a partial polarization of the emitted light, -­‐ an additional splitting caused by the magnetic field according to value of the magnetic quantum number, m, and -­ the bending of the electron trajectories into a helical path around the magnetic lines of forces. Different methods have been developed or have been extended to magnetic plasmas, such as numerical simulations and theoretical models. In our group, we have developed a fast numerical code to calculate combined Stark-­‐Zeeman line shapes, (the PPP-­‐B code, [1]).
Nevertheless, this code was originally designed for low Z emitters and the effect of the magnetic field is modeled either using the strong field approximation or the weak-­‐field approximation. Treating the Zeeman effect, as a perturbation of the isolated emitter is an approximation, which can be invalidated when the effects of the external magnetic field dominate over the spin-­‐orbit interaction (intermediate magnetic fields), [2]. Numerical simulations are currently used to solve such cases. Unfortunately, this technique is time consuming and thus impractical for the modeling of today’s highly complex plasma experiments that requires a numerically fast spectral line shape code.
The aim of this thesis is to investigate the spectroscopic properties of dense plasmas under magnetic fields. Atomic physics and plasma properties will be affected by such magnetic fields. A careful study of both aspects will help to extend the existing fast Stark-­‐Zeeman code to a new one designed for intermediate magnetic fields. This code will be appropriate for a wide range of plasma conditions to be useful for Intertial Fusion and Magnetic Fusion Experiments. This theoretical developments will be supported by numerical simulations when it is possible and by experimental results of laser driven capacitor-­‐coil targets experiments, [3].
Bibliography :
[1] S. Ferri et al., Frequency-­‐fluctuation model applied to Stark-­‐Zeeman spectral line shapes in plasmas, Phys. Rev. E 84, 026407 (2011).
[2] S. Ferri et al., C VI Lyman-­‐alpha line in presence of strong external magnetic field, communication in the Spectral Line Shape in Plasmas workshop (2015).
[3] S. Fujioka et al., Kilotesla magnetic field due to a capacitor-­‐coil target driven by high power laser. Scientific Reports, 3, 2013.