Precise measurement of first Townsend coefficient, using parallel plate avalanche chamber

By employing iso-C4H10 gas, we have studied the effective parameters in the first Townsend coefficient measurement using parallel plate avalanche chamber (PPAC). Obtained results are free from space charge and gap deformation effects, which have seriously affected previous PPAC-based measurements. The required conditions for a reliable Townsend coefficient measurement are presented as well.