  In this paper we report on a detailed study of ionization signals produced by
Compton electrons and alpha-particles in a Time Projection Chamber (TPC) flled
with different mixtures of liquid Argon and Nitrogen. The measurements were
carried out with Nitrogen concentrations up to 15% and a drift electric feld in
the range 0-50 kV/cm. A prediction for proton ionization signals is made by
means of interpolation. This study has been conducted in view of the possible
use of liquid Ar-N2 TPCs for the detection of gamma-rays in the resonant band
of the Nitrogen absorption spectrum, a promising technology for security and
medical applications.
