 Xenon is used as a " starter gas " in high pressure sodium lamps . It has the lowest thermal <unk> and lowest ionization potential of all the non @-@ radioactive noble gases . As a noble gas , it does not interfere with the chemical reactions occurring in the operating lamp . The low thermal <unk> <unk> thermal losses in the lamp while in the operating state , and the low ionization potential causes the breakdown voltage of the gas to be relatively low in the cold state , which allows the lamp to be more easily started . 
