As the need for scale-up in the provision of radiotherapy (RT) is clear, developing cost-effective and robust technologies for RT is ever more crucial. Novel proton- and ion-acceleration techniques based on high-power lasers can provide beams with unique characteristics. To make full use of a number of these techniques, the particles need to be converted efficiently into a beam.
This thesis describes work on the development of space-charge plasma lenses for capturing and focusing laser-driven protons and ions. A non-neutral electron plasma, which is confined by external electric and magnetic fields, generates transverse focusing. The work is undertaken as part of the LhARA project.
As a starting point, an existing prototype Gabor lens is modelled with particle-in-cell (PIC) simulations. It is found that an unstable plasma can lead to deleterious focusing effects comparable to those recorded previously in beam tests. A number of plasma instabilities is linked to the initial production of non-uniform electron clouds within the lens. Validation of the PIC code used to model confined plasmas is carried out using the results from experiments with low-density, magnetically-trapped electron clouds. The capabilities of the particle trap used throughout the experiments are characterised by measurements of the density, size, and evolution in time of the confined electron clouds.
This thesis also includes a first design of a normal-conducting solenoid suitable for LhARA. The magnet requires moderate to large power consumption due to Joule losses, in addition to a complex cooling system. These requirements are found to be particularly sensitive to the bore diameter and a strategy to reduce them with a transversely-graded coil is described.
Finally, the performance of plasma lenses and solenoids is evaluated by tracking a realistic laser-driven proton beam through the LhARA Stage~1 beam-line. Two models of the space-charge field produced by plasma lenses are presented.