Thermal surface neutralization of Fr ions with metal foils for magneto-optical trapping of radioisotopes

TL;DR

This study explores thermal surface neutralization of radioactive ions using metal foils, demonstrating yttrium's high efficiency for magneto-optical trapping of francium and rubidium atoms, with implications for radioactive atom manipulation.

Contribution

It provides experimental validation of yttrium foil's effectiveness in thermal neutralization, highlighting its superior release efficiency at elevated temperatures for radioactive atom trapping.

Findings

Yttrium foil achieves >65% neutral release efficiency.

Yttrium's neutralization efficiency exceeds 75% at 1350 K.

Neutralization efficiency depends on experimental conditions.

Abstract

We investigate neutralization processes (especially thermal surface neutralization), which are required for the magneto-optical trapping of radioactive atoms. A variety of neutralization methods are first summarized: neutral beam injection for fusion reactors, neutral atom implantation in semiconductor processing, and the production of radioactive neutral atoms in accelerators. We focus on thermal surface neutralization, which produces neutral atoms in the thermal energy range for laser cooling. The experiments were carried out with yttrium, gadolinium, and zirconium foils to neutralize francium and rubidium ions for magneto-optical trapping. The results reconfirm that yttrium foil is a good neutralizer (i.e., it has a neutral release efficiency $>65\%$). In addition, the release fraction when using yttrium foil exceeds 75\% at 1350 K, which is greater than the release fraction for the other foils. This reconfirmation is important because few previous studies have focused on thermal surface neutralization. Moreover, the results show that the neutralization efficiency is strongly influenced by the experimental process itself.