Studies of wire offset effects on gas gain in the ATLAS TRT straw chamber

Results of the measurements and simulation (both Analytical and Monte Carlo) ofthe amplification process in straw tubes in the ATLAS TransitionRadiation Tracker are presented. Main attention was paied to studies of the evolution of the signal amplitude spectrum for point ionisation as a function of the wireoffset in the TRT standard gas mixture. Good argreement of the experimental data and simulation points to a big step in understanding the intrinsic behaviour of the detector.