PhD opportunities

Absorption physics of intense twisted light with solid targets


Supervisor Dr Robert Kingham
Type Computational & Theoretical
Funding DTA (group or Dept/Faculty)
Info

PhD project for 2019

This project will explore how intense, picosecond-duration laser beams possessing orbital-angular momentum (OAM) interact with solid density plasma. Laser beams with OAM have ‘spiral’ phase-fronts (hence the term ‘twisted’ light) and each photon carries ±ℏ of angular momentum.  Such beams, and their interaction with matter, are well understood in conventional optics, where the intensity is low.  However, the study of what happens at the ultra-high, “relativistic” laser intensities ( I ≥ 1022 W/m2 ) used in laser-plasma interactions is still in its infancy. Most research focuses on the interaction of OAM pulses with under-dense plasma. This project will focus on their interaction with solid-density plasma. The idea is to explore how angular momentum in the laser affects the laser absorption efficiency, the characteristics of the energized electrons and magnetic-field generation.  These are fundamental processes that underpin a range of applications such as proton acceleration and advanced ICF schemes.  The investigation would be carried out using a combination of HPC simulations (using the particle-in-cell code EPOCH) and analytical theory. There may be opportunities to engage with experiments.

Kinetic modelling of divertor detachment in tokamaks including molecular effects


Supervisor Dr Robert Kingham 
Type Computational & Theoretical
Funding

EPSRC CASE top-up  (sponsored by CCFE)

Info

PhD project for 2019

Operating in the detached regime is crucial for the divertor to handle the energy and particle fluxes in the exhaust of tokamaks.  This will be an increasingly pressing issue in ITER and then DEMO. This project concerns detailed modelling of the interplay of kinetic parallel electron transport along magnetic fields lines in the scrape-off layer (SOL) with atomic & molecular physics occurring near the divertor.  The goal is to understand how detachment is affected by non-local effects (collisionless, superthermal electrons streaming from the separatrix to the divertor), especially its response to transient loading via ELMS.

The project will build upon the SOL-KiT code, which implicitly solves the Vlasov-Fokker-Planck equation for electrons and fluid equations for a single ion species along a field-line. It currently includes a collisional-radiative model for neutral atoms. However, in order to properly consider detachment, molecular physics (such as molecular activated recombination via D2+), impurity species and radiation, and charge-exchange are required. SOL-KiT will be upgraded to include these essential effects. The upgraded code will be used to investigate how kinetic effects influence energy, momentum and particle detachment, the parameter space for steady state detachment and its sensitivity and response to ELMs. It is anticipated that  insights from this 1D modelling can be incorporated into 2D fluid codes in the future. The PhD student would be primarily based at Imperial, but would frequently visit CCFE to integrate into their programme (theoretical & experimental).