Turbulent mix in inertial fusion and interstellar clouds – plasma strand project

Supervisor: Nigel Woolsey (University of York)

This project will suit someone with interests crossing fusion, plasma physics and astrophysics as well as an individual wishing to develop experimental and computation modelling skills. The project focus is on developing new high-energy-density experiments to study how turbulence evolves following the collision of a shock with a spherical object and apply scaling laws between the laboratory and astrophysical shock-cloud systems. An important aspect of this project is to provide measurements for testing inertial confinement fusion and astrophysics radiation- and magneto- hydrodynamic simulation models.

The experiments will use laser and pulse power systems to drive strong shocks and study turbulent flow as the shock passes a spherical obstacle. The aim is to work at larger scales and further develop x-ray phase contrast imaging techniques to gather data at very high resolution.  The turbulence, driven by strong shear flows, results in Kelvin-Helmholtz instabilities and flow vorticity. Similar processes occur in imploding inertial confinement fusion capsules and at stellar and galactic scales as shocks and winds pass gravitationally bound dense clouds. In both cases, this results in the mixing of materials. This is problematic for fusion as the contamination of the deuterium-tritium fuel with heavier elements, such as carbon, from the shell material containing the fuel increases cooling radiative preventing target ignition. In astrophysics mixing is necessary for distribution of heavy elements or ‘metals’ across the interstellar medium and turbulence may trigger gravitational collapse leading to stellar formation.

As part of this project, you will join a larger group in developing laser-produced short-burst and bright sources of x-rays for phase contrast imaging measurements.  This technique enables the measurement of material interfaces in low-density and low atomic number materials at high-spatial and temporal resolution.  We use laser facilities across the world and work with groups in the UK, the rest of Europe, USA and China.

This image above shows an x-ray phase contrast image of a shock moving through a plastic block and driven from the right. In this project we will design experiments to study the plasma flow after a shock or blast wave collides with a spherical obstacle. The intention is to drive strong shear flows across the surface of the sphere and study the emergence of turbulent flow and material mixing. The experiment design offers good diagnostic access, which is helpful for testing computational models, and through design as well as the use low atomic number materials has direct relevance to astrophysical shock-cloud interactions.

This project is York based and offers opportunities to travel to experiments, collaborative meetings and conferences. Experiments run for periods from a few days to several weeks.

Skills the student would learn during the PhD include:

  • Work with a diverse technical and scientific team across a number of cultural regions
  • Build effective communication skills and networking.
  • Acquire formal communication skills through poster and oral presentations at conferences and the writing of reports and papers.
  • Develop laser-plasma experimental, diagnostic and data analysis expertise.
  • Develop detailed understanding of compressible hydrodynamics in inertial fusion and astrophysics.

This project is offered by University of York. For further information please contact Prof. Nigel Woolsey at: nigel.woolsey@york.ac.uk and send a short email outlining your interest in this project.