Electron Drift Velocity in the μBooNE TPC

As the readout time associated with a trigger of μBooNE is proportional to the drift time, it is important to know the drift velocity precisely. Likewise, the reconstruction of track position from the drift time of ionization electrons depends on knowledge of the drift velocity. The nominal drift field in μBooNE is E = 500V/cm, and the peak electric field at the surface of the collection wires is about VV Y /a ln(b/a) = 400/0.015 ln(0.3/0.015) ≈ 9 kV/cm. Electron drift velocities in liquid argon for have reported in [1, 2, 3, 4, 5, 6, 7]. A comparison of many of these measurements was made by Walkowiak [6], as shown in fig. 1. Kalinin et al., and also Walkowiak, fit the measurements to a function that parameterizes the electron drift velocity v with respect to the electric field E and temperature T ,