target that interacts firstly with the laser prepulse, this ionises the target turning it into a plasma and causing a pre-expansion of the target front. Which produces an underdense plasma region at the front of the target, the so-called preplasma. Once the main laser pulse arrives at the target front it will then propagate through this underdense region and be reflected from the front surface of the target propagating back through the preplasma. Throughout this process the laser has heated up the electrons in the underdense region and accelerated them via stochastic heating. This heating process is incredibly important, producing a high temperature electron populations is key for the next steps of the process. The importance of the preplasma in the electron heating process has recently been studied both theoretically and experimentally showing how longer preplasmas lead to stronger electron heating and an enhancement in TNSA. The hot electrons propagate through the solid target and exit it through the rear end. In doing so, the electrons produce an incredibly strong electric field, in the order of TV/m, through charge separation. This electric field, also referred to as the sheath field due to its resemblance with the shape of a sheath from a sword, is responsible for the acceleration of the ions. On the rear face of the target there is a small layer of contaminants (usually light hydrocarbons and water vapor). These contaminants are ionised by the strong electric field generated by the hot electrons and then accelerated. Which leads to an energetic ion beam and completes the acceleration process. Comparison with RF acceleration The advantage of plasma acceleration is that its acceleration field can be much stronger than that of conventional radio-frequency (RF) accelerators. In RF accelerators, the field has an upper limit determined by the threshold for dielectric breakdown of the acceleration tube. This limits the amount of acceleration over any given area, requiring very long accelerators to reach high energies. In contrast, the maximum field in a plasma is defined by mechanical qualities and turbulence, but is generally several orders of magnitude stronger than with RF accelerators. It is hoped that a compact particle accelerator can be created based on plasma acceleration techniques or accelerators for much higher energy can be built, if long accelerators are realizable with an accelerating field of 10 GV/m. Plasma acceleration is categorized into several types according to how the electron plasma