Protons can be accelerated to MeV energies via the interaction of high power lasers with plasma. These experiments typically use thin foils as targets and film-based particle detectors. With the development of high power lasers with repetition rates of 10s or even 100s of Hertz, which enable high resolution mapping of the interaction parameter space, these conventionally-used targets and diagnostics are not practical. The development of new targetry - such as kHz compatible liquid sheet targets - and the use of active diagnostics is essential for the development of laser-driven high repetition rate proton sources and their applications. Recent preliminary experiments have also shown that using liquid targets results in proton beams with highly desirable characteristics, including significantly less divergence than solid targets. My PhD research will look at developing high repetition rate proton sources, in particular studying the use of liquid targets.