Exploration and Development of Laser-driven X-ray Backlighter Sources and Imaging Techniques – Plasma Strand Project
Supervisors – Chris Murphy (University of York) and Phillip Thomas (AWE).
Fusion energy has the capability to revolutionise the energy landscape with the potential to provide energy with advantages in terms of fuel availability, safety and environmental impact. Research in inertial fusion – specifically with high power lasers – has surpassed multiple milestones in the last decade, with many advances being achieved at the National Ignition Facility (NIF) at the Lawrence Livermore National Lab (LLNL). Much of the success may be attributed to improved understanding of the dynamics of fuel compression achieved using advanced diagnostics. Some diagnostics, such as neutron downshift spectroscopy, are only practicable once significant fusion yield (or even ignition) has already been achieved. Laser-based X-radiography is useful for smaller test facilities and is currently implemented on the NIF, but has limited resolution due to the x-ray generation mechanism implemented. This project will aim to produce x-ray sources tuned to the needs of fusion capsule radiography in order to help develop further advances in inertial fusion energy, including at test facilities where ignition is not the final aim.
Laser wakefield acceleration (LWFA) is a mechanism by which lasers can generate beams of relativistic electrons over relatively short distances. Such electron beams have been shown to produce x-ray sources with unique properties through bremsstrahlung, inverse Compton scattering, and betatron oscillations. Such sources may prove useful in developing novel diagnostic approaches for inertial fusion experiments.
The proposed project would begin by studying implosion noise, instability dynamics and areal density, in order to develop the source requirements in terms of flux, resolution and photon energy. Once a desired parameter range has been identified, LWFA combined with one or more of the above x-ray generation mechanisms will be studied an the feasibility of each will be determined. Once selected, an optimisation process would be developed in an attempt to overcome any traditional weaknesses of the mechanism. For example, low photon energy in betatron, low flux in ICS, and large source size in the case of bremsstrahlung. Target design would be completed using hydrodynamics simulations in combination with the EPOCH code for the plasma physics processes. Diagnostic development in order to accurately measure the flux, spectrum and source size of the sources would likely be developed in tandem with the source. The targets and detectors would be fielded in laser facilities in the UK, Europe and the USA in collaboration with AWE, LLNL and other suitable partners depending on the facility requirements. The fielding of coded apertures would enhance the diagnostic capabilities at AWE, giving it a unique capability to image high energy X-rays and neutrons without the required high temperature and neutron yield.
The project will mainly be based in York, but will involve experimental campaigns at high power laser labs which are almost always collaborative. This might include travel to Oxfordshire, Sweden, France, Romania and the USA amongst other laboratories and universities. There will also be the opportunity to attend summer schools and conferences internationally.
During the first six months of the PhD, students will typically travel to undertake taught modules at all of the Fusion CDT partner universities.
This project is offered by University of York. For further information please contact: Chris Murphy (chris.murphy@york.ac.uk).
This project may be compatible with part time study, please contact the project supervisors if you are interested in exploring this.
For details on how to apply, please visit: Apply
Image above is from: CID Underwood et al., Plasma Phys. Control. Fusion 62 (2020) 124002, https://doi.org/10.1088/1361-