Studies of thorium and ytterbium ion trap loading from laser ablation for gravity monitoring with nuclear clocks

TL;DR

This paper demonstrates laser ablation loading of thorium ions into a trap, exploring its potential for compact nuclear clock development, and compares it with ytterbium ion loading, highlighting the process's efficiency and surface effects.

Contribution

It presents the first successful laser ablation loading of thorium ions into a linear Paul trap, analyzing yield evolution and surface depletion effects relevant for nuclear clock technology.

Findings

Successful detection of 232Th+ and 232Th2+ ions from plasma plumes.

Thorium ablation yield shows strong depletion, indicating oxide layer removal.

Results align with similar experiments on other elements and oxides.

Abstract

Compact and robust ion traps for thorium are enabling technology for the next generation of atomic clocks based on a low-energy isomeric transition in the thorium-229 nucleus. We aim at a laser ablation loading of single triply ionized thorium in a radio-frequency electromagnetic linear Paul trap. Detection of ions is based on a modified mass spectrometer and a channeltron with single-ion sensitivity. In this study, we successfully created and detected 232Th+ and 232Th2+ ions from plasma plumes, studied their yield evolution, and compared the loading to a quadrupole ion trap with Yb. We explore the feasibility of laser ablation loading for future low-cost 229Th3+ trapping. The thorium ablation yield shows a strong depletion, suggesting that we have ablated oxide layers from the surface and the ions were a result of the plasma plume evolution and collisions. Our results are in good agreement with similar experiments for other elements and their oxides.