Measurement of electron mobility in liquid and critical argon at low electric-field strengths.

Abstract

The mobility of excess electrons in argon has been determined from drift-time measurements using the pulse-shape method. The electrons were alternatively generated by ionization or pulsed photoemission. The measurements have been performed in liquid argon on the liquid-vapor coexistence curve at temperatures between 110 K and the critical temperature ${\mathit{T}}_{\mathit{c}}$=151 K at field strengths between 3 and 133 V ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. At the mobility maximum, observed at about ${\mathit{T}}_{\mathit{c}}$-5 K, an increase of the mobility down to a field strength of 3 V ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ is found, whereas for temperatures away from the mobility maximum the low-field mobility is independent of field strength. A high-precision temperature-regulation system allowed for an approach to ${\mathit{T}}_{\mathit{c}}$ to within 2 mK. The low-field mobility at ${\mathit{T}}_{\mathit{c}}$ is determined to be ${\mathrm{\ensuremath{\mu}}}_{\mathit{c}}$\ensuremath{\approxeq}150 ${\mathrm{cm}}^{2}$${\mathrm{V}}^{\mathrm{\ensuremath{-}}1}$${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$.