| Summary: | Since the first studies of target-normal sheath acceleration around the year 2000, production of energetic ion beams from intense laser-matter interactions has been investigated in great depth. New acceleration mechanisms such as radiation pressure acceleration, collisionless shock acceleration, the hybrid breakout afterburner mechanism, and special regimes such as light-sail radiation pressure acceleration have been discovered and demonstrated. Applications of ion beams produced by these mechanisms range from common diagnostic techniques for laser plasma interactions to industrial radiography and even—albeit needing significant improvements to predictability and reproducibility before this can be realised—their proposed use in medical treatments like hadron therapy, which if successful could significantly reduce the cost to hospitals of hosting such therapies. I present work on three topics around laser-accelerated ion beams and their applications:
Firstly, I present an experiment which sought to demonstrate acceleration of ions from a laser-driven collisionless shock within a plasma produced from low-density plastic foam. This acceleration mechanism produces ions with a narrow energy spectrum, compared to the more well-established target-normal sheath acceleration. Despite limitations to the accessible experimental conditions, I present evidence that ions were accelerated with the narrow energy spectrum characteristic of this mechanism.
Secondly, I introduce the reader to an important application of fast ion beams: the proton radiography diagnostic. This diagnostic is used to measure the electromagnetic fields present in a plasma through their influence on a beam of protons as it traverses the plasma. I explain the theory of proton radiography and describe a laser-plasma channelling experiment on which proton radiography was used to probe the magnetic fields associated with a laser-produced plasma channel. I demonstrate the analysis of some proton radiographs using an improved solver I have implemented in a community analysis package.
Finally, I propose improving the information accessible to the proton radiography diagnostic by making observations of the plasma from several different directions, a procedure I term ‘proton tomgraphy’. I then derive methods of improving the quality of data recovered from proton tomography. Compared to standard tomographic algorithms I achieve an orders-of-magnitude improvement in reconstrution quality of synthetic data when very few lines of sight are available
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