1D Simulations of the helicon double layer

Double-layers (DLs) are electrostatic structures able to support a potential jump in a narrow spatial region of plasmas. Recently some laboratories have reported about a current-free DL obtained by a helicon-source plasma expansion along a diverging magnetic field. Their findings can lead eventually to development of innovative space propulsion system. Experiment has shown evidence of DL in case of floating boundary conditions and biased boundary conditions. To study DL Layer formation and stability and its application to spacecraft thruster a new 1-D PIC code has been developed and implemented. The new algorithm solves for the Boltzmann density parameter and, in case of a Neumann (floating) boundary condition, the surface charge density simultaneously as it solves for the discretized electrostatic potential. Stability is demonstrated for timesteps exceeding the electron plasma period.