Development of a recoil ion source providing slow Th ions including 229(m)Th in a broad charge state distribution

Raphael Haas,Anna Viatkina,Dennis Renisch,Wenbing Li,Ferdinand Schmidt-Kaler,Felix Stopp,Tom Kieck,Christoph E Düllmann,Dmitry Budker,Karin Groot-Berning

doi:10.1007/s10751-019-1688-2

Abstract

Ions of the isomer 229mTh are a topic of high interest for the construction of a “nuclear clock” and in the field of fundamental physics for testing symmetries of nature. They can be efficiently captured in Paul traps which are ideal for performing high precision quantum logic spectroscopy. Trapping and identification of long-lived 232Th+ ions from a laser ablation source was already demonstrated by the TACTICa collaboration on Trapping And Cooling of Thorium Ions with Calcium. The 229mTh is most easily accessible as α-decay daughter of the decay of 233U. We report on the development of a source for slow Th ions, including 229mTh for the TACTICa experiment. The 229mTh source is currently under construction and comprises a 233U monolayer, from which 229mTh ions recoil. These are decelerated in an electric field. Conservation of the full initial charge state distribution of the 229mTh recoil ions is one of the unique features of this source. We present ion-flight simulations for our adopted layout and give a final source design. This source will provide Th ions in their original charge state at energies suitable for capture in a linear Paul trap for spectroscopy investigations.

Highlights

The 229mTh became a nuclide of high interest in the field of quantum physics in recent years because of its low-energy isomeric nuclear state [1]
The combination of the ablation and recoil ion sources offers the possibility to study a variety of Th isotopes in several charge
The kinetic energy of the 229mTh recoil ions of about 84 keV has to be reduced before the ions enter the Paul trap to allow their capture

Summary

Introduction

The 229mTh became a nuclide of high interest in the field of quantum physics in recent years because of its low-energy isomeric nuclear state [1]. Whereas in [4,5,6,7], 229Th3+ has been successfully extracted as low-energy ion beam from a buffer-gas-stopping-cell based setup, this approach cannot be used for deceleration in our setup due to the gas load, which is incompatible with the pressure requirements in the TACTICa Paul trap. This technique leads to a loss of the higher charge states, which are of interest for spectroscopic investigations of the isomeric state. The combination of the ablation and recoil ion sources offers the possibility to study a variety of Th isotopes (see Fig. 1) in several charge

Electrostatic deceleration

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Final design

Conclusion

Findings

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