I briefly sketch the principle of a fusion reactor, and provide answers to the above general questions. This often gives rise to extensive discussions, which I welcome.
Fusion research is a truly international mission-oriented development.
However, the physics research program is certainly big. It is very broad and interdisciplinary. There are strong links with astrophysics, fluid dynamics, and the plasma physics that is encountered in industrial processes. Taking measurements of plasma properties such as temperature and density, in a plasma at a temperature of 100 Million degrees, is a research field in itself, in which the most advanced techniques are used.