A systematic study of electron drift for gaseous chamber design

We present a consistent set of measurements of electron drift velocities and Lorentz deflection angles in all noble gases with methane and ethane as quenchers in magnetic fields up to 0.8 Tesla. These and many other results are available in a searchable database on the World Wide Web at http://cyclotron.mit.edu/drift/ to allow for guided design and optimization of future detectors. A simple model is used to form an empirical parameterization of the results. This compact form unifies the drift characteristics of a gas mixture over a range of electric (0-1.5 kV/cm) and magnetic (0-0.8 Tesla) fields. A more detailed model is presented which explains the surprisingly large effect of even modest (and inevitable) nitrogen contamination on electron drift velocity. Additional measurements and simulations confirm the validity of the model's predictions and show possible applications.