Linear particle accelerators use electric fields to accelerate particles. However, these can only reach a certain value, as otherwise a breakdown occurs and, locally, a plasma is generated for a short time. Plasma wakefield accelerators can generate electric fields that are orders of magnitude higher, thus enabling a much more compact design. The amplitude of the electric field is related to the electron plasma density, so that the highest possible density is desirable. Helicon discharges generate the highest densities in linear geometry. Interestingly, the heating mechanism is not well understood. This DFG-funded project aims on a better physical understanding of the heating process. To this end, the DFG-funded doctoral thesis of Luis Carlos Herrera Queseda will carry out numerical investigations accompanied by experimental studies at the University of Greifswald and the University of Wisconsin-Madison.