Effects of Electron Impact on Ionization of Short-Lived Isotopes in a Hot Cavity

A Monte Carlo method based numerical model of hot cavity surface ion source that takes into account radioactive decay and the delay due to the sticking of particles to ionizer surface is considered. The influence of electron impact ionization by thermionic electrons accelerated by the extraction field is investigated. It is shown that the contribution from that process rises with decreasing half-life period and cannot be neglected, especially for substances of small surface ionization coefficient. The changes of relative yields from electron impact and surface processes with the length of the average sticking time are also studied.