I. Charge on an Anode Wire

In this analysis we assume 100 MeV/c electrons and protons, traveling in straight-line trajectories through a straw detector. Each track traverses a straw at an average sterio angle of α~50 ° with respect to the axis of the straw. The diameter of the straw is 5 mm. Therefore we assume the average track length is 70 % of diameter divided by sin(α), the primary ionization charge is fully collected, and ion recombination during the charge drift is ignored. The gas is assumed to be a mixture of argon/ethane ~ 60/40, so that the number of ion pairs created by a minimum ionizing particle, MIP, is 126 per cm. This provides a Landau distribution of the charge, which is then deposited on the anode. The average number, 69, of primary electrons {[126 × 0.5/cos(α)] × 0.7}, is spread over the drift time[1,2]. A simulation[3] of the ionization is shown as Fig 1, which applies a Vavalov distribution to the mean ionization of an MIP and a proton in 1cm of the gas. Note in this figure that the most probable energy loss for protons is ~24 times that for an MIP