Modeling of electron emission processes accompanying radon-α-decays within electrostatic spectrometers

Electrostatic spectrometers utilized in high-resolution β-spectroscopy studies such as in the Karlsruhe Tritium Neutrino (KATRIN) experiment have to operate with a background level of less than 10^-2 counts per second. This limit can be exceeded by even a small number of ^219,220Rn atoms being emanated into the volume and undergoing α-decay there. In this paper we present a detailed model of the underlying background-generating processes via electron emission by internal conversion, shake-off and relaxation processes in the atomic shells of the ^215,216Po daughters. The model yields electron energy spectra up to 400 keV and electron multiplicities of up to 20 which are compared to experimental data.