bipolar versus unipolar shaping of MDT signals

The MDT frontend electronics scheme, as presented in the TDR, was optimized for fast liner gases like Ar/N2/CH4 91/4/5, but since these gases contain hydrocarbons which seem to be responsible for aging problems, the current baseline gas is Ar/CO2 93/7 which shows nice aging properties but is slower and very nonlinear. The different pulse shapes as well as the fact that trailing edge information and double track separation information were not found to be very useful made a complete review of the frontend electronics specification necessary.