Improving the energy resolution of a time-of-flight (TOF) spectrometer used to measure the energy of positron induced electrons

The energy resolution of a TOF spectrometer used to measure the energy of electrons varies nonlinearly with the energy of the electron. This resolution degrades for large kinetic energies as the difference in flight times among high energy electrons becomes comparable to the inherent timing resolution of the spectrometer. This is often solved by extending the flight paths of the electrons or by applying a negative DC potential, thus slowing down the electrons and spreading the flight times. Increasing the length of the flight path may not be feasible in all cases due to experimental constraints, whereas a constant negative bias precludes the detection of electrons with energies less than the potential applied. Here, we investigate, using SIMION®, the feasibility of increasing the energy resolution of a TOF spectrometer by applying a time varying negative potential aimed at increasing the time interval between the flight times of the electrons without stopping any electrons from reaching the electron detector. We model a TOF spectrometer used to measure the energy of positron-induced electrons and show that, through the application of an appropriate time varying potential, we are able improve the energy resolution without causing spectral modification.