Applying machine learning methods for the analysis of two-dimensional mass spectra

In a measurement of isomeric yield-ratios in fission, the Phase-Imaging Ion-Cyclotron-Resonance technique, which projects the radial motions of ions in the Penning trap (JYFLTRAP) onto a position-sensitive micro channel plate detector, has been applied. To obtain the yield ratio, that is the relative population of two states of an isomer pair, a novel analysis procedure has been developed to determine the number of detected ions in each state, as well as corrections for the detector efficiency and decay losses. In order to determine the population of the states in cases where their mass difference is too small to reach full separation, a Bayesian Gaussian Mixture model was implemented. The position-dependent efficiency of the micro-channel plate detector was calibrated by mapping it with 133Cs+ ions, and a Gaussian Process was trained with the position data to construct an efficiency function that could be used to correct the recorded distributions. The obtained numbers of counts of excited and ground-state ions were used to derive the isomeric yield ratio, taking into account decay losses as well as feeding from precursors.

Automated summary

The Phase-Imaging Ion-Cyclotron-Resonance technique was used to measure isomeric yield-ratios in fission by projecting ion motions onto a position-sensitive micro channel plate detector. A new analysis procedure was developed to determine the number of detected ions in each state, and corrections for detector efficiency and decay losses were applied. A Bayesian Gaussian Mixture model was implemented to calculate the population of states with small mass differences. The efficiency of the detector was calibrated and an efficiency function was constructed to correct the recorded distributions.