Ionic mobility dispersion in KCD digital radiography: dopants and physical parameters

摘要

Abstract: The spatial resolution of the Kinestatic Charge Detector (KCD) for digital radiography is limited by mobility dispersion when the detector operates with noble gases such as xenon or krypton. The magnitude and dependence on drift distance of the peak widths of ionic signal pulses produced in the KCD provide a measure of mobility dispersion. These parameters have been measured in a KCD filled with krypton gas at a pressure of 60 atm, and in the same gas alternately doped with 1.7% of each of the following amine additives: ammonia, methylamine, dimethylamine and trimethylamine. The ionization potentials of these dopants are 10.2, 9.0, 8.2 and 7.8 ev, respectively. While the undoped medium exhibited significant mobility dispersion, all four of the amine- doped media showed dramatic reduction or elimination of mobility dispersion.!19