Dr Robin Timmis from the Department of Physics has been awarded the Institute of Physics’ Culham Thesis Prize: Plasma Physics Group. The annual prize recognises a well-explained thesis that demonstrates a good understanding of the subject and shows significant new work and originality.
Explaining her thesis entitled ‘Attoseconds and the exascale: on laser plasma surface interactions’, she comments: ‘We sit on the verge of exascale revolutions in both laser facility and supercomputing powers. These rapid rises over the past few decades have driven forward the frontiers of high-energy-density physics, with applications ranging from fusion and lab-based astrophysics to biomedical imaging and photolithography. But even with such resources, we are approaching fundamental limits in feasible peak intensities for our brightest infrared sources, extreme X-ray sources, and ultrashort attosecond pulses. This calls for the development of new technologies.’
In her thesis, Dr Timmis explores a promising alternative: the reflection of a laser off a relativistically oscillating plasma surface, which produces extremely bright attosecond X-ray pulses. She used theory, simulations, and experiments to explore this phenomenon examining how laser energy is absorbed by the plasma in the highly relativistic regime and how it can generate bright attosecond structures, of both electron bunches and radiation bursts.
Dr Timmis’ thesis presents two experiments: one at ORION, where the group measured the absolute intensity of the X-ray harmonics, and the second at Gemini, for which she mapped out the experimental plan, however had to submit her thesis during the beamtime for the experiment.
‘After completing my doctorate, I analysed the exciting results of that experiment, which have recently been accepted for publication in Nature,’ she adds. ‘Through careful control of the plasma conditions, we generated harmonics three orders of magnitude brighter than previous measurements and discovered a new regime of harmonic generation. The energies that we measured are sufficient to support the generation of a “coherent harmonic focus”, which boosts the peak electromagnetic field intensity by many orders of magnitude. It has been suggested that this mechanism offers a realistic solution for the generation of extreme electromagnetic fields. We have demonstrated that this source is possible in principle. If it could be harnessed on a next-generation exascale system, the light could be intense enough to directly probe the quantum vacuum and therefore test fundamental properties of the universe.’
Dr Robin Timmis joins fellow Oxford laureates of the prize Dr Thomas Gawne (2024), Dr Alex Picksley (2023) and Dr James Chappell (2022).