Direct detection of live 244 Pu and 60 Fe on Earth as a monitor for recent heavy element nucelosynthesis A. Wallner

Transcription

1 Direct detection of live 244 Pu and 60 Fe on Earth as a monitor for recent heavy element nucelosynthesis A. Wallner The Australian National University (ANU)

2 Extraterrestrial Radionuclides on Earth Can we find isotopic fingerprints of the ISM (interstellar medium) in terrestrial archives? Radionuclides contain time information as they can serve as radioactive clocks!

3 r-process sites? Hubble NASA core collapse supernova rates: ~ 1000:1 neutron star mergers

4 Actinides pure r process nuclides AMS accelerator mass spectrometry background-free!?! 80 Myr most sensitive technique for long-lived radionuclides NS-NS rate: SN rate: per year in our galaxy 0.02 per year in our galaxy atom counting of 60 Fe, 244 Pu rate ratio SN : NS-NS = 1000:1

5 Extraterrestrial Radionuclides on Earth recent uptake into terrestrial archives extremely low growth rate (mm/myr) integrate over tens of Myr efficiently enrich content of ocean water column remote locations low terrestrial background deep-sea mangenese crusts & sediments oceanexplorer.noaa.gov

6 New crust sample for 244 Pu 25 cm 2 (110 g): 1ct (TU Munich 2000) now: 250 cm 2 (1.8 kg):?? AMS at Univ. of Vienna Layer 1 (0-0.5 Myr) Layer 2a (0.5-5 Myr) Layer 2b (5-12 Myr) Layer 3 (12-25 Myr) Layer 4: hydro-thermal blank?

7 SN-isotope 244 Pu- new results? Possible observatories of ISM on Earth: 1. Deep-sea sediments : 2. Deep-sea nodules and crusts : AMS results for 244 Pu-search: detector events TUM: C. Wallner et al. 2000/03 Pacific ferromanganese nodules 1 ct Rehovot: M. Paul et al Pacific sediment 1 ct* new: new: Rehovot / VERA-Vienna Pacific sediment 1 ct TUM / VERA-Vienna Pacific ferromanganese crust 0 & 1+1 ct 240 ( < 600, 2σ limit ) 244 Pu ats/cm 2 /Myr *fits to anthropogenic production Wallner et al. 2014

8 Status: 244 Pu in terrestrial crust: 100:1 estimated vs measured crust: dust collection over 25 Myr 244 Pu: time window - alive a few 100 Myr neutron star mergers?

9 Supernova-produced radionuclides on Earth - Live! GEOLOGICAL ISOTOPE ANOMALIES AS SIGNATURES OF NEARBY SUPERNOVAE Ellis, J., Fields, B.D., Schramm, D.N., ApJ 470, 1227 G. Korschinek et al., Radiocarbon 38(1): (1996) B.D. Fields, 2004 New Astron. 48, & 2005 Long-lived radionuclides (T 1/2 Ma) WHERE to look for: e.g. 60 Fe from SN: ice core sediments deep sea crusts Which isotopes: Korschinek, Knie et al. 26 Al, 53 Mn, 60 Fe, 146 Sm, 182 Hf, 244 Pu, 247 Cm

10 Supernova-produced radionuclides on Earth - Live! nearby supernova: < 100 pc, rate ~ (Ma) -1 ( 182 Hf, 244 Pu...) ( 60 Fe...) C. Wallner et al. (2000) Crab-nebula (SN from 1054 AD) Supernova Remnant at 2000 pc distance

11 60 Fe-signal in a deep-sea crust AMS at Munich Peak at 2-3 Myr! AMS measurement of 60 Fe content of crust at TU Munich background level the only lab yet!

12 Eurogenesis European Collaborative Research Programme = Origin of the Elements and Nuclear History of the Universe SN produced radionuclides collaboration - AMS: ANU (Canberra): Wallner, Fifield, Tims VERA (Univ. Vienna): Feige, Wallner, Steier, Winkler HZDR Dresden (Merchel, Rugel) cf. - similar programme at TU Munich

13 2 new sediment cores from the Indian Ocean Thanks to C. Sjunneskog (FSU)! Myr J. Feige s PhD 10 Be 26 Al 53 Mn 60 Fe, AMS in progress SN signal? 0 & 10 Myr

14 AMS measurements VERA (3 MV) - Vienna ANU (15 MV) - Canberra 10 Be, 26 Al 60 Fe, 53 Mn + Dresden: 10 Be & chemistry

15 Half-life value of 60 Fe

16 Half-life measurements problematic: very long half-lives & decay pattern; interference, background, isotopic & isobaric background AA(tt) = dddd dddd = λλ NN(tt) AA(tt) = λλ NN 0 ee λλ tt AA(tt) = λλ NN(tt) NN ssssssssssss NN ssssssssssss AMS at ANL MS: ICPMS, AMS, TIMS,...

17 Independent approach: 55 Fe is well known and easily measured with AMS ( 55 Mn no stable neg. ion) measure radionuclides, both as detector countrates use the same detector AA(tt) = λλ A 66 = λ 66 NN(tt) NN ssssssssssss NN ssssssssssss 66 FF 55 FF 55FF AMS E3 Position 2

18 Half-life value of 60 Fe: AA(tt) = λλ NN(tt) NN NN ssssssssssss ssssssssssss? ICPMS? AMS A 66 = λ FF 55 FF 55FF AMS AMS

19 Blank measurements (no 60 Fe) - ANU commercial Fe (metal oxide) blank level: 0.6x10-16

20 Preliminary results for Supernova-search see poster by Jenny Feige Supernova-Produced 26 Al and 60 Fe in Deep-Sea Sediments from the Indian Ocean signal of 60 Fe

21 Collaboration: Univ. of Vienna: J. Feige, R. Golser, W. Kutschera, F. Quinto, P. Steier, G. Wallner ANU (Canberra, AU): L.K. Fifield, S. Tims GAMS (TU Munich): T. Faestermann, G. Korschinek, K. Knie Racah Institute of Physics, Hebrew U. (Jerusalem): M. Paul, A. Ofan, C. Feldstein Atominstitut (Vienna): M. Bichler, J. Sterba Helmholtz Center (Dresden/Rossendorf): S. Merchel, G. Rugel PSI (Villigen, CH): D. Schumann, R. Dressler

22 Nucleosynthesis in the Lab neutrons, protons, α irradiations Postdoc (Level A or ANU PhD ANU Geel / Belgium Frankfurt / Germany Vienna / Austria AMS measurements ANU Debrecen / Hungary SARAF / Israel