Abstract: A Geiger-Mueller ("GM") tube containing a noble gas mixture of about 98-99.9% Ne and the remainder Ar, and in addition containing from 2-5% ethylene as the quench gas, provides high stability and high count rates in the temperature range from about -100.degree. C. to about 200.degree. C. When this GM tube is provided with a sleeve-and-screen liner in electrical contact with an outer cathode, the tube exhibits exceptional sensitivity. The sleeve may be a continuous deposit of a heavy metal having an atomic number from about 73 to about 83, deposited on the inner surface of the cathode tube, or the sleeve may be a foil liner of tungsten or tantalum. The screen is woven of metal wire on which is deposited a heavy metal.