A light source to be powered by microwave energy, the source having: • a solid plasma crucible of material which is lucent for exit of light therefrom, the plasma crucible having a sealed, central void in the plasma crucible, • a Faraday cage surrounding the plasma crucible, the cage being at least partially light transmitting for light exit from the plasma crucible, whilst being microwave enclosing, • a fill in the void of material excitable by microwave energy to form a light emitting plasma therein, • an antenna arranged within the plasma crucible for transmitting plasma-inducing microwave energy to the fill, the antenna having: • an antenna connection extending outside the plasma crucible for coupling to a source of microwave energy; • a source of microwaves at a frequency to excite resonance within the lucent crucible and the Faraday cage for excitation of a light emitting plasma in the sealed void; and • a waveguide (31, 34) for coupling microwaves from the generator to the antenna, the waveguide being: • substantially two or more half wave lengths long and having: • a waveguide input from the generator positioned close to an input end of the waveguide and • a waveguide output to the antenna connection comprising a microwave conductor positioned close to an output end of the waveguide, the microwave conductor comprising: a resonator portion and an output portion, the resonator portion turning through a right angle to the output portion, the output portion being located at half the height of the waveguide, passing through an end wall of the waveguide and extending as the antenna connection - • a solid plasma crucible of material which is lucent for exit of light therefrom, the plasma crucible having a sealed, central void in the plasma crucible, • a Faraday cage surrounding the plasma crucible, the cage being at least partially light transmitting for light exit from the plasma crucible, whilst being microwave enclosing, • a fill in the void of material excitable by microwave energy to form a light emitting plasma therein, • an antenna arranged within the plasma crucible for transmitting plasma-inducing microwave energy to the fill, the antenna having: • an antenna connection extending outside the plasma crucible for coupling to a source of microwave energy; • an antenna connection extending outside the plasma crucible for coupling to a source of microwave energy; • a source of microwaves at a frequency to excite resonance within the lucent crucible and the Faraday cage for excitation of a light emitting plasma in the sealed void; and • a waveguide (31, 34) for coupling microwaves from the generator to the antenna, the waveguide being: • substantially two or more half wave lengths long and having: • a waveguide input from the generator positioned close to an input end of the waveguide and • a waveguide output to the antenna connection comprising a microwave conductor positioned close to an output end of the waveguide, the microwave conductor comprising: a resonator portion and an output portion, the resonator portion turning through a right angle to the output portion, the output portion being located at half the height of the waveguide, passing through an end wall of the waveguide and extending as the antenna connection - • substantially two or more half wave lengths long and having: • a waveguide input from the generator positioned close to an input end of the waveguide and • a waveguide output to the antenna connection comprising a microwave conductor positioned close to an output end of the waveguide, the microwave conductor comprising: a resonator portion and an output portion, the resonator portion turning through a right angle to the output portion, the output portion being located at half the height of the waveguide, passing through an end wall of the waveguide and extending as the antenna connection - a resonator portion and an output portion, the resonator portion turning through a right angle to the output portion, the output portion being located at half the height of the waveguide, passing through an end wall of the waveguide and extending as the antenna connection -