Helicon Plasma Thrusters are a suitable propulsion device for low thrust and moderate specific impulse requirements, they are conceptually simple, compact and don't require cathodes nor neutralizer making for a reliable system. In the framework of this thesis the mechanism of acceleration of plasma in the region known as magnetic nozzle was studied. Particle-In-Cell is a numerical method for rarefied gas an plasma suitable for this cases, simulations were conducted with different PIC codes, Starfish and ProPic and later compared with experimental measurements found in literature. In collaboration with T4i and CISAS thrust measurements were made to further validate the numerical results.