Microwave plasma reactor for manufacturing synthetic diamond material

A microwave plasma reactor for manufacturing synthetic diamond material via chemical vapour deposition, the microwave plasma reactor comprising:

• a plasma chamber defining a resonant cavity for supporting a primary microwave resonance mode having a primary microwave resonance mode frequency f;
• a plurality of microwave sources coupled to the plasma chamber for generating and feeding microwaves having a total microwave power PT into the plasma chamber;
• a gas flow system for feeding process gases into the plasma chamber and removing them therefrom;
• and
• a substrate holder disposed in the plasma chamber and comprising a supporting surface for supporting a substrate on which the synthetic diamond material is to be deposited in use,
• wherein the plurality of microwave sources are configured to couple at least 30% of the total microwave power PT into the plasma chamber in the primary microwave resonance mode frequency f, and wherein at least one of the plurality of microwave sources is a magnetron and at least some of the plurality of microwave sources are solid state microwave sources provided to tune or tailor an electric field within the plasma chamber.