Time-Resolved Interstellar Pu-244 and Fe-60 Profiles in a Be-10 Dated Ferromanganese Crust

Mr Dominik Koll1,2, Prof. Dr. Anton Wallner1,2, Dr. Michael Hotchkis3, Mr. David Child3, Prof. Dr. Keith Fifield1, Dr. Michaela Froehlich1, Mr. Michi Hartnett1, Dr. Johannes  Lachner2, Dr. Silke Merchel1,2,4, Dr. Stefan Pavetich1, Dr. Georg Rugel2, Dr. Zuzana Slavkovska1, Dr. Stephen Tims1

1Research School of Physics, Australian National University, Canberra, Australia, 2Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, 3Australian Nuclear Science and Technology Organisation, Sydney, Australia, 4Faculty of Physics, University of Vienna, Vienna, Austria

More than 20 years have passed since the first attempts to find live supernova Fe-60
(t1/2 = 2.6 Myr) in a deep-sea ferromanganese crust [1]. Within these 20 years, strong evidence was presented for a global influx of supernova dust into several geological samples around 2 Myr ago. Recently, a much younger continuous influx was found in Antarctic snow and in deep-sea sediments [2-4] and an older peak around 7 Myr in deep-sea crusts [5,6].

The long-lived isotope Pu-244 (t1/2 = 80 Myr) is produced in the astrophysical r-process similarly to most of the heaviest elements. Although the production mechanism is believed to be understood, the astrophysical site is heavily disputed. Most likely scenarios involve a combination of rare supernovae and neutron star mergers. The search for Pu-244 signatures in samples with known Fe-60 signatures allows to test for either common influx patterns or independent Pu-244 influxes disentangled from stellar Fe-60. Accordingly, this information provides a unique and direct experimental approach for identifying the production site of the heavy elements.

Very recently and first reported in the AMS-14 conference, the first detection of interstellar Pu-244 was published [6]. This was only feasible by achieving the highest detection efficiencies for plutonium in AMS ever reported [7]. The achieved time resolution of 4.5 Myr integrates over the supernova influxes and is therefore not high enough to unequivocally show a correlated influx pattern of Fe-60 and Pu-244.
Based on this progress, we are now aiming to measure highly time-resolved profiles of Fe-60 and Pu-244 in the largest ferromanganese crust used so far. Results on the characterization of the crust including cosmogenic Be-10 (t1/2 = 1.4 Myr) dating and a 10 Myr profile of interstellar Fe-60 including the confirmation of the 7 Myr influx will be presented along with first data on interstellar Pu-244.

[1] Knie et. al., Phys. Rev. Lett. 83 (1999).
[2] Koll et al., Phys. Rev. Lett. 123 (2019).
[3] Koll et al., EPJ 232 (2020).
[4] Wallner et al., PNAS 117 (2020).
[5] Wallner et al., Nature 532 (2016)
[6] Wallner et al., Science 372 (2021)
[7] Hotchkis et al., NIMB 438 (2019)


Biography:

I’m Dominik Koll, born in Germany, did physics at Technical University of Munich (TUM) and graduated with high distinction in Nuclear-, Particle- and Astrophysics from TUM in 2018 (Master of Science).
I came to Australia in 2018 and started my PhD at the Nuclear Physics Department of ANU. From September this year I am working at the Helmholtz-Zentrum Dresden-Rossendorf as a dual-PhD candidate of ANU and HZDR. I’m experienced in nuclear astrophysics, environmental radioactivity and (radio)chemistry, all with focus on accelerator mass spectrometry.

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Date

Nov 19 2021

Time

FRIDAY
8:45 am - 9:45 am