Suppression of the internal Conversion Decay of Th-229m (FY19Q1 report)

Technical Report · Tue Jan 08 04:00:00 EST 2019

DOI:https://doi.org/10.2172/1491980· OSTI ID:1491980

Friedrich, Stephan ^[1]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

To measure the decay energy of metastable Th-229m, we had proposed to modify an existing experiment by placing a MgF₂ crystal between our U-233 source and a high-resolution STJ photon detector. Metastable Th-229m nuclei produced in the decay of U-233 would be absorbed in the MgF₂, but since the MgF₂ bandgap of ~10eV exceeds the energy of the metastable state, decay by internal conversion is expected to be suppressed. Th-229m can then only decay by gamma emission, and the ~7.8 eV gamma energy can be transmitted through the MgF₂ and detected by the STJ detector. The spectra are calibrated with a pulsed 355 nm laser.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: AC52-07NA27344
• OSTI ID: 1491980
• Report Number(s): LLNL-TR--765340; 955347
• Country of Publication: United States
• Language: English

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