  In this paper we report on the evidence for ionization track signals from
cosmic ray muons and Compton electrons in a Time Projection Chamber (TPC)
filled with liquid Argon and doped with different fractions of Nitrogen. This
study has been conducted in view of the possible use of liquid Argon/Nitrogen
TPCs for the detection of gamma rays in the resonant band of the Nitrogen
absorbtion spectrum, a promising technology for security and medical
applications.
