The new MRTOF mass spectrograph following the ZeroDegree spectrometer at RIKEN's RIBF facility

TL;DR

The paper reports on the development and initial testing of a high-resolution MRTOF mass spectrograph at RIKEN, capable of analyzing short-lived nuclei with high precision and introducing new optimization and ion selection techniques.

Contribution

It presents a newly assembled MRTOF-MS with optimized voltage control and an innovative in-system ion selection method, enhancing performance for nuclear mass measurements.

Findings

Achieved mass resolving power > 1,000,000 within 12.5 ms

Successfully measured over 70 nuclear masses during commissioning

Demonstrated capability to study short-lived nuclei with low-lying isomers

Abstract

A newly assembled multi-reflection time-of-flight mass spectrograph (MRTOF-MS) at RIKEN's RIBF facility became operational for the first time in spring 2020; further modifications and performance tests using stable ions were completed in early 2021. By using a pulsed-drift-tube technique to modify the ions' kinetic energy in a wide range, we directly characterize the dispersion function of the system for use in a new procedure for optimizing the voltages applied to the electrostatic mirrors. Thus far, a mass resolving power of $R_m > 1\,000\,000$ is reached within a total time-of-flight of only $12.5\,\mathrm{ms}$, making the spectrometer capable of studying short-lived nuclei possessing low-lying isomers. Detailed information about the setup and measurement procedure is reported, and an alternative in-MRTOF ion selection scheme to remove molecular contaminants in the absence of a dedicated deflection device is introduced. The setup underwent an initial on-line commissioning at the BigRIPS facility at the end of 2020, where more than 70 nuclear masses have been measured. A summary of the commissioning experiments and results from a test of mass accuracy will be presented.