Plasmas are used in many areas, including plasma etching, medical treatment and diagnostics, agricultural treatment and will be essential in obtaining a working fusion reactor. In the lab, it is crucial to understand the structure of a plasma. Some existing diagnostic techniques, such as Langmuir probes and spectroscopic techniques, allow for some characterisation of the plasma but they also have their disadvantages. This project aims to determine the feasibility of another method of characterisation using the positron beamline at ANU.
The student will model how a positron beam interacts with a plasma, with the goal to characterise the energy distribution of plasma electrons using a positron beam. There are several different measurements that are possible, including lifetime spectroscopy or annihilation doppler broadening spectroscopy.
The project can be adjusted to the requirements or aspirations of the student. In increasing order of complexity, the student will model annihilation of:
- positrons of fixed energy in a homogeneous plasma.
- a distribution of positrons at different energies in a homogeneous plasma.
- an experimental geometry including a spatially varying distribution of positrons and plasma energies.
The simulation techniques will include simple analytical models through to microscopically-motivated Monte Carlo tracking of the particles.