Extended temperature range fluorescent lamp

An extended temperature operating range low pressure discharge lamp comprising:

• an envelope containing an ionizable medium at a selected pressure;
• an electrode sealed at each end of said envelope for sustaining an electric discharge through said ionizable medium;
• a volume variation control for varying the volume of said ionizable medium within said envelope in response to variations in temperature within said envelope, wherein said selected pressure may be maintained within said envelope over an extended temperature range, wherein said volume variation control includes at least one control volume containing a specified volume of said ionizable medium and an aperture communicating between said envelope and said at least one control volume, wherein said at least one control volume includes a sliding piston for varying the volume of said ionizable medium within said envelope in response to movement thereof.