1 Direct Pb isotopic analysis of a nuclear fallout debris particle from the 2 Trinity nuclear test 3 4 5 Jeremy J. Bellucci1*, Joshua F. Snape1, Martin W. Whitehouse1, Alexander A. Nemchin1,2 6 7 *Corresponding author, email address:
[email protected] 8 9 1Department of Geosciences, Swedish Museum of Natural History, SE-104 05 10 Stockholm, Sweden 11 2 Department of Applied Geology, Curtin University, Perth, WA 6845, Australia 12 13 Abstract 14 15 The Pb isotope composition of a nuclear fallout debris particle has been directly 16 measured in post-detonation materials produced during the Trinity nuclear test by a 17 secondary ion mass spectrometry (SIMS) scanning ion image technique (SII). This 18 technique permits the visual assessment of the spatial distribution of Pb and can be used 19 to obtain full Pb isotope compositions in user-defined regions in a 70 µm x 70 µm 20 analytical window. In conjunction with BSE and EDS mapping of the same particle, the 21 Pb measured in this fallout particle cannot be from a major phase in the precursor arkosic 22 sand. Similarly, the Pb isotope composition of the particle is resolvable from the 23 surrounding glass at the 2σ uncertainty level. The Pb isotope composition measured in 24 the particle here is in excellent agreement with that inferred from measurements of green 25 and red trinitite, suggesting that these types of particles are responsible for the Pb isotope 26 compositions measured in both trinitite glasses. 27 28 29 Keywords: 30 31 Trinitite, Trinity Test, Post Detonation Nuclear Forensics, Pb isotopes, SIMS, Scanning 32 Ion Imaging, Fallout Debris, Forensics 33 34 35 Introduction 36 37 In the event of a non-state sanctioned nuclear attack, forensic investigations will 38 be necessary to determine the provenance of the weapon and the materials used in 39 construction of the device.