Abstract: Ions injected into a multipole RF trap (where they are neutralized in charge-exchange reactions) are proposed to be used to determine the energy of electrons from the decay of the ²²⁹Th isomer. A conversion electron is emitted within a few microseconds after neutralization. A deceleration spectrometer with magnetic collimation coupled with the ion trap is planned to be used to determine the electron energy. The spectrometer’s design and the results from modeling are discussed.