The commissioning and performance of the Notre Dame Multi-Reflection Time-of-Flight Mass Spectrometer*

The future N = 126 factory at Argonne National Laboratory aims to produce many isotopes on the neutron-rich side of the nuclear chart utilizing multi-nucleon transfer reactions. Especially, it can provide many important neutron-rich nuclei around the N = 126 abundance peak of the astrophysical rapid neutron capture process. Some experiments, such as high-precision mass measurements, benefits from nearly isobaric-free ion beams. To remove the isobaric contaminants, a multi-reflection time-of-flight mass spectrometer (MR-TOF) has been built and successfully commissioned off-line at the University of Notre Dame and has reached a resolving power of 70,000, with an efficiency of 10%. This resolving power could potentially be improved by better ion optics or power supplies stability. The low efficiency is due to the large beam emittance and potential misalignment in the off-line commissioning setup. Based on extensive ion-optics simulations, with the low emittance beam provided by the cooler-buncher as well as better alignment and power supplies stability, the MR-TOF can reach a resolving power of over 100,000 with an efficiency of 100%. Better performance of the MR-TOF is expected in the following online commissioning at Argonne National Laboratory.