CHARGE COLLECTION AND ENERGY RESOLUTION STUDIES IN COMPRESSED XENON GAS NEAR ITS CRITICAL-POINT

We have built a 4.5 1 high purity Xe gas ionization chamber and operat ed it at pressures of up to 62 atm (1.4 g/cm3) at room temperature. Th is thermodynamic regime in pure xenon has not previously been studied. Ionization from a Bi-207 internal conversion electron source was drif ted over distances of 2.7 and 5.0 cm in two separate gridded ionizatio n chambers within the gas volume. We observed that there was less than 1% difference in the charge collected from these two detectors at the same electric field strength. Energy resolution measurements were per formed over the range of xenon densities from 0.49 to 1.40 g/cm3 at se veral electric field strengths. An electronic noise subtracted resolut ion of 16 keV FWHM was measured for the 976 keV Bi-207 internal conver sion line at an electric field strength of 1.3 kV/cm in compressed xen on gas near its critical density.