# Characterization of $^{233}$U alpha recoil sources for $^{229(m)}$Th beam production

## TL;DR

This study characterizes $^{233}$U alpha recoil sources for $^{229}$Th production, revealing low recoil efficiencies and the importance of source composition and contamination, using multiple spectroscopic techniques.

## Contribution

It introduces a comprehensive spectroscopic approach to evaluate and understand the performance of $^{233}$U alpha recoil sources for $^{229}$Th beam production.

## Key findings

- Low $^{229}$Th recoil efficiencies observed
- Contamination layer identified on the source surface
- Spectroscopic methods effectively assess source performance

## Abstract

Radioactive $^{233}$U alpha recoil sources are being considered for the production of a thorium ion source to study the low-energy isomer in $^{229}$Th with high-resolution collinear laser spectroscopy at the IGISOL facility of the University of Jyv\"askyl\"a. In this work two different $^{233}$U sources have been characterized via alpha and gamma spectroscopy of the decay radiation obtained directly from the sources and from alpha-recoils embedded in implantation foils. These measurements revealed rather low $^{229}$Th recoil efficiencies of only a few percent. Although the low efficiency of one of the two sources can be attributed to its inherent thickness, the low recoil efficiency of the second, thinner source, was unexpected. Rutherford backscattering spectrometry (RBS) was performed to investigate the elemental composition as a function of depth revealing a contamination layer on top of the thin source. The combination of spectroscopic methods proves to be a useful approach in the assessment of alpha recoil source performance in general.