Simulation Study of Time-Walk Issues for Drift Tubes

Time walk is evaluated for a drift tube of 2.9 cm in diameter filled with P10 gas, with an anode wire of 70 µm in diameter. Its magnitude, if the shaping is of Poisson type and a leading-edge discriminator is used, is found to be 2-10 ns when 50% gain variation is allowed in the gas multiplication. On the other hand, the use of a constant fraction timing discriminator is expected to reduce this to the order of 0.1 ns.