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 lucent crucible having a sealed void therein; • a microwave-enclosing Faraday cage surrounding the lucent crucible, the cage being at least partially light transmitting for light exit therethrough from the lucent crucible; • a fill in the void of material excitable by microwave energy to form a light emitting plasma therein; • an antenna arranged within the lucent crucible for transmitting plasma-inducing microwave energy to the fill, the antenna having: • a connection extending outside the lucent crucible for coupling to a source of microwave energy; • agenerator of microwaves for excitation of a light emitting plasma in the sealed void, the generator having an output for microwaves; characterised in that the light source is also having: • an electrical conductor of constant cross sectional area passing from the output of the generator to the connection of the antenna; and • means for attaching the generator to the lucent crucible, the attachment means having: • a passage with a conductive wall (3,4) extending from the generator output to the antenna connection, the electrical conductor passing along the passage and the passage being configured as two parts: • a first part in which there is an air gap between the conductive wall and the electrical conductor and • a second part in which there is a spacer between the conductive wall and the electrical conductor; wherein the conductor forms with the conductive passage a transmission line for microwave energy from the generator to the lucent crucible for excitation of the plasma therein. • a solid plasma crucible of material which is lucent for exit of light therefrom, the lucent crucible having a sealed void therein; • a microwave-enclosing Faraday cage surrounding the lucent crucible, the cage being at least partially light transmitting for light exit therethrough from the lucent crucible; • a fill in the void of material excitable by microwave energy to form a light emitting plasma therein; • an antenna arranged within the lucent crucible for transmitting plasma-inducing microwave energy to the fill, the antenna having: • a connection extending outside the lucent crucible for coupling to a source of microwave energy; • a connection extending outside the lucent crucible for coupling to a source of microwave energy; • agenerator of microwaves for excitation of a light emitting plasma in the sealed void, the generator having an output for microwaves; characterised in that the light source is also having: • an electrical conductor of constant cross sectional area passing from the output of the generator to the connection of the antenna; and • means for attaching the generator to the lucent crucible, the attachment means having: • a passage with a conductive wall (3,4) extending from the generator output to the antenna connection, the electrical conductor passing along the passage and the passage being configured as two parts: • a first part in which there is an air gap between the conductive wall and the electrical conductor and • a second part in which there is a spacer between the conductive wall and the electrical conductor; • a passage with a conductive wall (3,4) extending from the generator output to the antenna connection, the electrical conductor passing along the passage and the passage being configured as two parts: • a first part in which there is an air gap between the conductive wall and the electrical conductor and • a second part in which there is a spacer between the conductive wall and the electrical conductor; • a first part in which there is an air gap between the conductive wall and the electrical conductor and • a second part in which there is a spacer between the conductive wall