Departmental Seminar

Diagnosing hydrogen plasma in a high power helicon device

Mr Campbell Strachan
Australian National University

The International Thermonuclear Experimental Reactor (ITER) is expected to be completed and perform net energy gain fusion reactions in 2035. This reactor, along with its successor, DEMO, require novel heating techniques to achieve the targeted 150 million Kelvin. One type of the heating devices is the Neutral Beam Injector system (NBIs). Negative ion density sources are required as positive ion neutralisation is inefficient at the challenging energy beam target of 1 MeV. Surface production techniques are used to produce negative ions through high atomic and positive ion densities collision on caesiated substrate grids. These ions and atomic species are in turn generated through high power RF Inductively Coupled Plasmas (ICPs), up to 100 kW. Helicon Coupled Plasmas (HCPs) are similar to ICPs but are capable of generating higher density plasma for the same RF input powers. This could increase the efficiency of the NBI sources but have not been well characterized at the design parameters set by ITER.

The purpose of this study is to characterise HCPs within the design restrictions at high powers up to 20 kW for feasibility of possible use in future NBIs. At these powers, measurements are conducted using non-intrusive diagnostic techniques where possible. This includes: atomic temperature measurements via excited atomic neutrals using Tuneable Diode Absorption Spectroscopy (TDLAS); Optical Emission Spectroscopy (OES) for gas temperature; and power transfer efficiency under different operating conditions. These measurements are used with an extended global model in order to understand reaction pathways, power deposition and other plasma properties. In this presentation I will give an overview of these systems and the initial results of several spectroscopic, power and probe measurements in higher power HCP using MAGPIE. These measurements are compared with theoretical calculations from the developed global model.

Zoom details: https://anu.zoom.us/j/87125702788?pwd=Ni96TnJNSUxXTEU2VjkvYU10ZElHUT09
 
Meeting ID: 871 2570 2788
Password: 924466

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