Electron Avalanche in Liquid Xenon

We Present detailed measurements of the electron-avalanche process in liquid xenon. The measurements were made by using liquid-xenon-filled proportional chambers with anode diameters of 2.9, 3.5, and 5.0 {μ} to detect 279-keV γ rays and measure the photopeak pulse height as a function of applied voltage. The use of uniform pulses of electrons enabled us to discriminate against secondary Townsend processes. We present a table of the first Townsend coefficient α as a function of electric field E; a typical value is α=(4.5±0.3)×10⁴ cm^-1 at E=2×10⁶ V/cm. The electron avalanche occurs in liquid xenon at electric fields 27 ±{} 3 times smaller than would be predicted using measurements made in gaseous xenon and Eρ density scaling.