ELECTRON-DRIFT VELOCITIES AND ELECTRON MOBILITIES IN FAST ROOM-TEMPERATURE DIELECTRIC LIQUIDS AND THEIR CORRESPONDING VAPORS

The drift velocity, w, of excess electrons as a function of the applied uniform electric field, E, in liquid tetramethylsilane (TMS), 2,2,4,4-tetramethylpentane (TMP), tetramethyltin (TMT), and in mixtures of TMS with TMP (molar ratio, M = 1.31/1) and n-pentane (M = 102/1; 17/1; 5.6/1) has been measured up to E-values of ∼ 105 V cm-1 or density (N)-reduced ele ctric held E/N-values of ∼ 3 × 10-17 V cm2. The maximum w attained for these liquids, and the corresponding values of E are: 7.2 × 106 cm s-1 at 125 kV cm-1 for TMS, 6.0 × 106 cm s-1 at 75 kV cm-1 for TMS, 2.6 × 106 cm s-1 at 115 kV cm-1 for TMP, 3.2 × 106 cm s-1 at 105 kV cm-1 for TMS/TMP (M = 1.31/1), 6.8 × 106 cm s-1 at 105 kV cm-1 for TMS/n-pentane (M = 102/1), 6.8 × 106 cm s-1 at 145 kV cm-1 for TMS/n-pentane (M = 17/1), and 4.9 × 106 cm s-1 at 145 kV cm-1 for TMS/n-pentane (M = 5.6/1). The thermal-electron mobilities in the above liquid media are respectively 119.3, 85.7, 31.8, 39.1, 118, 85, and 47.6 cm2 s-1 V-1. Also, w was measured as a function of E/N for TMS, TMP, and neopentane vapors at room temperature and is compared with that in the corresponding liquids. Properties of these media which make them desirable for radiation detectors are discussed. © 1990.