How Nature makes gold

Transcription

1 How Nature makes gold The role of isotopes for the origin of the elements Karlheinz Langanke GSI Helmholtzzentrum Darmstadt AAAS Symposium, Vancouver, February 20, 2012

2 Signatures of Nucleosynthesis solar abundance distribution NUCLEAR ASTROPHYSICS is concerned with the origin of elements in stellar burning nucleosynthesis processes nucleosynthesis history of our universe Abundance the production of energy in stars and stellar explosi stellar H-, He, C, O, Si-burning stars, supernovae s-process He-burning in AGB stars, massive stars r-process type II supernovae, merging neutron stars The stellar abundance distribution is a reflection of nuclear structure and nuclear stability! 10-5 cosmic rays p-process site disputed A observational signatures are n clear stabilit! abundance distributions luminosities

3 What is an Isotope? unstable due to beta decay For a given number of protons, isotopes differ by their number of neutrons

4 Nucleosynthesis processes

5 Star at the end of its life Star has an onion-like structure Iron is the end-product of stellar burning After nuclear energy source has ceased, stellar core collapses under its gravity SUPERNOVA

6 Supernova collapse and explosion In about a second, the core radius reduces from 6000 km to 20 km Collpase stops when the inner core corresponds to a gigantic nucleus with about half of a solar mass. Most of the gain in gravitational energy is released in the explosion. This energy corresponds to the production of 100 Suns during their entire life of 10 Billion years.

7 Supernova Simulation Recent progress: Multi-dimensional hydrodynamics Improved nuclear input Electron capture Neutrino-induced reactions Courtesy: Hans-Thomas Janka Courtesy chans-thomas Janka

8 Electron capture during collapse Capture rates on nuclei vs free protons Modern many-body models predict electron capture rates which differ by more than a magnitude from previous estimates. Consequence: capture on (unstable) neutron-rich isotopes dominate through the entire collapse with significant impact on neutrino spectra and temperature-density profiles of the core

9 Stellar electron capture Stable nuclei are unstable under stellar conditions Data from charge-exchange reactions: (n,p), (d,2he)

10 Making radioactive isotopes

11 (p,n) charge-exchange reactions on rare isotopes M. Sasano, R.G.T. Zegers et al. PRL 107, (2011) Extract Gamow-Teller strengths model-independently Weak reaction rates for late stellar evolution (supernovae) First successful experiment: 56 Ni(p,n) to extract Gamow-Teller strengths for supernova unstable isotope n RI beam New method for (p,n) in inverse kinematics: applicable to exotic nuclei of any mass and excitation ti energy. Inverse kinematics Requires beam intensities >10 4 pps Explore very neutron rich nuclei in next generation RI beam facilities i like FRIB@MSU

12 Neutron Stars: supernova remnants Neutron Stars are laboratories for matter at extreme densities Neutron rich nuclei Equation of State for nuclear matter Exotic phases?

13 Explosive hydrogen burning Binary system of compact object and companion star in hydrostatic burning. Mass flow induces thermonuclear explosion White Dwarf Nova Neutron Star x-ray burster Integral satellite Observation of gamma lines; e.g. from electron-positron annihilation following beta+ (positron) decay of unstable nuclei like 18 F

14 Novae: Explosive H burning TUDA 18 F(p, ) 15 O DRAGON Affects 22 Na and 26g Al radioisotope ejecta from classical novae reduced uncertainty for 511 kev spectrum in classical novae 14

15 Precision mass measurements Isoltrap at CERN Penning trap Mass measurements performed in Jyvaeskylae, Finland, for rp-process

16 Rp-process process masses Rp-process mass flow Effect on abundance predictions

17 Making Gold! Nature vs Humans Old stars in galactic halo have the same r-process abundances as the solar system for A>130, but not below. Johann Friedrich Böttger, Alchemist Inventor of European White China In Meissen, Germany two distinct r-process sites?

18 The R-Process Masses Half lives Neutron capture rates Fission Neutrino reactions Courtesy: K.-L. Kratz

19 Potential r-process sites Neutrino-driven wind from a nascent neutron star in a supernova explosion Neutron star mergers Freiburghaus et al. Woosley et al.

20 R-Process at high entropy: fission Courtesy: Gabriel Martinez-Pinedo

21 Next-Generation Isotope Facilities TRIUMF/ ISAC MSU/FRIB GSI/FAIR RIKEN/ RIBF

22 GSI today UNILAC SIS 18 New facility FAIR SIS 100/300 ESR Super FRS CBM Rare-Isotope Production Target HESR PP / AP Antiproton Production Target Ion beams today: Z = 1 92 (Protons til uranium) Up to 2 GeV/nucleon 100 m RESR CR Future beams: FLAIR Intensity: primary ions 100-fold secondary RIB fold Types : Z = NESR (Antiprotons til uranium) Energies: ions up to GeV/u antiprotons 0-15 GeV/c

23 Mass measurements at FAIR

24 The RIB Chance: New Horizons