Radiation aging studies of CO2 hydrocarbon mixtures for the SLD drift chamber

The SLD drift chamber requires a `slow´ drifting gas and low diffusion to allow wave form digitization. CO₂ provides this but requires an admixture of a quencher to provide more gain. A test chamber with an 8 sense wire cell, such as will appear in the final chamber, was exposed to an X-ray tube while containing a variety of binary admixtures of CO₂: 8% isobutane, 8% ethane, and 2% isopropanol. It was determined that adding small fractions of water (⩽0.66%) or isopropanol (1-2%) to the CO₂: 8% ethane, or 8% isobutane extended the useful life of the chamber so that integrated charge collections of ~1 C/cm are permissible. Results and discussions are presented