Studies of the stability and systematics of operation of the DELPHI plastic streamer tubes

The influence of different factors, such as pressure and temperature, slight changes in a gas mixture, self-sustaining discharge, aging and different deviations in the detector geometry, on the operation of the DELPHI plastic streamer tubes was studied. The contributions of these factors to the energy resolution of the DELPHI hadron calorimeter were estimated. The major influence was found to be due to atmospheric pressure fluctuations. The scale of a signal change is ≅±1% per -+1 Torr, which is comparable with the intrinsic resolution of the hadron calorimeter of ≅8-10% at 100 GeV. The question of the choice of a gas mixture was studied as well. The maximum streamer charge was shown to be independent of component concentrations in the Ar:CO2:isobutane (or n-pentane) gas mixtures. (orig.)