Direct detection of the ∼ 8.4 eV internal conversion energy of 229mTh embedded in a superconducting nanowire

Published

August 25, 2025

Author(s)

Galen O'Neil, Kjeld Beeks, Eric Hudson, David Ray Leibrandt, Marion Mallweger, Sae Woo Nam, Sayan Patra, Gil Porat, Dileep Venkatarama Reddy, Thorsten Schumm, Stephen Schoun, Benedict Seiferle, Christian Schneider, Lars von der Wense, Peter Thirolf, Varun Verma, Jun Ye, Chuankun Zhang

Abstract

We report on a direct measurement of the ∼ 8.4 eV nuclear excitation energy of the isomeric first excited state 229mTh via the internal conversion (IC) decay channel. Thermalized and mass-filtered recoiling 229mTh ions from 233U α decay are delivered to the surface of a superconducting nanowire sensor and become embedded. The ion is neutralized, triggering the IC decay, and the energy released by the IC decay is detected with high quantum efficiency by the nanowire sensor. Energy resolution is enabled by the current dependence of the internal quantum efficiency of the nanowire sensor. The techniques presented here are complementary to light-based detection schemes. The IC decay channel is about eight orders of magnitude faster than the photo-emission channel, thus the ability to detect IC decays with high efficiency with superconducting nanowire sensors is likely to be a valuable tool for future 229mTh experiments.

Citation

Physical Review C

Volume

112

Pub Type

Journals

Download Paper

https://doi.org/10.1103/9v5w-b8k2

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Keywords

isomer, nuclear, nanowire, snspd, vuv, thorium

Citation

O'Neil, G. , Beeks, K. , Hudson, E. , Leibrandt, D. , Mallweger, M. , Nam, S. , Patra, S. , Porat, G. , Venkatarama Reddy, D. , Schumm, T. , Schoun, S. , Seiferle, B. , Schneider, C. , von der Wense, L. , Thirolf, P. , Verma, V. , Ye, J. and Zhang, C. (2025), Direct detection of the ∼ 8.4 eV internal conversion energy of 229mTh embedded in a superconducting nanowire, Physical Review C, [online], https://doi.org/10.1103/9v5w-b8k2, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959746 (Accessed September 27, 2025)