Related projects

"Numerical simulation of the Helicon Double Layer Thruster Concept"
ESA ARIADNA ITT AO4919 05/3201 A (2006-2007).

This research program was focused on a numerical investigation on acceleration of plasma provided by an helicon source into vacuum . The analysis has been conducted through a combination of 1-D and 2-D code numerical code. A 1-D code named PPDL was developed specifically for the porpoise of this study. It is an hybrid code with Boltzmann electrons and drift-kinetic ions, inclusion of dominant 2-D effects and high computational efficiency through implicit nonlinear Boltzmann solver. With the hybrid Boltzmann electron/drift-kinetic ion approach, the time step is only limited by ion period which is two orders of magnitude larger than electron plasma period and ion gyro period which can become very short.

Simulations have been performed with several models for thrusters to identify the critical parameters. The effects of ions and electrons temperatures, magnetic field strength and gradient. The plasma density and plasma source rates have been changed as well. The 2D model adopted in this study is the Object Oriented Particle in Cell Code (OOPIC). The hybrid configuration has been found to not fulfill our requirements therefore we had to use the full PIC method, where electrons are computed as real particles like ions. The geometry has been defined as near as possible to the experimental apparatus, like the properties of electrons and ions that are charged with Maxwellian distributions inside the source tube. The static magnetic field has been reconstructed adopting two coils with shape and current as reported by Charles, in order to have a axial field inside the source with two peaks of almost 150G.

We have conducted three campaigns of simulations with growing source rates and ions densities. The first two campaigns shown the main border conditions’ effects on the plasma potential and ions velocity distribution. We have changed the electrons and ions temperatures, the electrical properties of the source walls, neutral pressure, magnetic field and plasma production rates and distributions. The third campaign has been devoted to the evaluation of higher densities plasmas with biased left source walls and, enlarging the diffusion chamber length, the thrust and specific impulse.

The results show a high energy ions flux at almost two times the ion sound speed. The potential jump is larger than the experimental measurements and, sometimes, lower. The effect of the neutral pressure increase, which reduces the high energy flux, appears similar to the one reported by Charles while the magnetic field has not been able to switch it off. The combined approach resulted very useful since the 1-D code has been used to screen many different experimental conditions and to identify the right boundary conditions and the 2-D code has been then used to refine 1-D results.

This program has been completely funded by ESA in the frame of Ariadna program.

"Understanding of the physics and numerical simulation of helicon double layer thruster concept"
ESA ARIADNA ITT AO4919 05/3201CCN (2008-2009)

Aim of this study is to analyze coupling between EM field generated by the helicon antenna and plasmas and to develop a kit of code suitable to preliminary design an helicon thrusters. The problem of simulating completely into detail an helicon plasma thruster is huge, very complex and yet unresolved. In this study a kit of code able to provide a thruster design will be developed based on:

1. 1-D wave code to simulate plasma wave interaction, power deposition and mode conversion,
2. Fokker-Plank solver code to simulate ion-wave interaction,
3. plasma source global model to simulate to simulate the plasma source evolution,
4. 1-D PIC code to analyze plasma expansion into vacuum.

This program has been partially funded by ESA in the frame of Ariadna program.

References

ARIADNA Projects
Numerical Simulation of the Helicon Double Layer Thruster Concept