Two-dimensional beam profile monitor for the detection of alpha-emitting radioactive isotope beam

TL;DR

This paper introduces a novel two-dimensional beam profile monitor using a microchannel plate and CCD to distinguish alpha-emitting radioactive isotope beams from other ions, improving beam detection in nuclear experiments.

Contribution

The study develops a new BPM capable of separating alpha-emitting radioactive isotope beams from similar mass reaction products, enhancing detection in nuclear physics experiments.

Findings

Successfully separated Fr+ beam from reaction products.

Able to observe alpha decay of Fr isotopes distinctly.

Technique applicable to other alpha-emitter beams for medical use.

Abstract

Ions with similar charge-to-mass ratios cannot be separated from existing beam profile monitors (BPMs) in nuclear facilities in which low-energy radioactive ions are produced due to nuclear fusion reactions. In this study, we developed a BPM using a microchannel plate and a charge-coupled device to differentiate the beam profiles of alpha-decaying radioactive isotopes from other ions (reaction products) produced in a nuclear reaction. This BPM was employed to optimize the low-energy radioactive francium ion (Fr+) beam developed at the Cyclotron and Radioisotope Center (CYRIC), Tohoku University, for electron permanent electric dipole moment (e-EDM) search experiments using Fr atoms. We demonstrated the performance of the BPM by separating the Fr+ beam from other reaction products produced during the nuclear fusion reaction of an oxygen (18O) beam and gold (197Au) target. However, as the mass of Au is close to that of Fr, separating the ions of these elements using a mass filter is a challenge, and a dominant number of Au+ renders the Fr+ beam profile invisible when using a typical BPM. Therefore, by employing the new BPM, we could successfully observe the Fr+ beam and other ion beams distinctly by measuring the alpha decay of Fr isotopes. This novel technique to monitor the alpha-emitting radioactive beam covers a broad range of lifetimes, for example, from approximately 1 s to 10 min, and can be implemented for other alpha-emitter beams utilized for medical applications.