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 COz: 8% isobutane, 8% ethane, and 2% isopropanol. It was determined that adding small fractions of water (5 O.SSY) o or isopropanol (l-2%) to the CO2: 8% ethane, or 8% isobutane extended the useful life of the chamber so that integrated charge collections of Ll C/cm are permissible. Results and discussions are presented.