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Nuclear Astrophysics with fast radioactive beams

Nuclear Astrophysics with fast radioactive beams. Hendrik Schatz Michigan State University National Superconducting Cyclotron Laboratory Joint Institute for Nuclear Astrophysics JINA. Outline: rp-process r-process. Accreting neutron stars. Bursts and other nuclear processes

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Nuclear Astrophysics with fast radioactive beams

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  1. Nuclear Astrophysics with fastradioactive beams Hendrik SchatzMichigan State University National Superconducting Cyclotron Laboratory Joint Institute for Nuclear Astrophysics JINA • Outline: • rp-process • r-process

  2. Accreting neutron stars • Bursts and other nuclear processes • probe M,R, cooling • dense matter EOS, superfluidity, meson condensates, quark matter strange matter Companion star(H + He envelope) Accretion disk(H and He fallonto neutron star) Superbursts X-ray bursts Neutron star(H and He burninto heavier elements)

  3. Uncertain models due to nuclear physics Galloway et al. 2003 97-98 2000 Burst models withdifferent nuclear physicsassumptions Woosley et al. 2003 astro/ph 0307425 Need much more precise nuclear data to make full use of high quality observational data Reality check: Burst comparison with observations Precision X-ray observations(NASA’s RXTE)  GS 1826-24 burst shape changes !(Galloway 2003 astro/ph 0308122)

  4. Nuclear physics needed for rp-process: (ok – but corrections needed) • b-decay half-lives • masses • reaction ratesmainly(p,g), (a,p) (in progress) (just begun) some experimental information available(most rates are still uncertain) Theoretical reaction rate predictions difficult neardrip line as single resonances dominate rate: Hauser-Feshbach: not applicable Shell model: available up to A~63 but large uncertainties (often x1000 - x10000) (Herndl et al. 1995, Fisker et al. 2001)  Need radioactive beam experiments (various methods, ISOL and fast beams)

  5. H. Schatz 2+ 89.9 keV New experimental techniques at NSCL applied to 32Cl(p,g)33Ar Shell model calculation: predicted level Herndl et al. 1995 experimentally known level 3.97 MeV 5/2+ Dominate ratein rp-process 3.56 MeV 7/2+ gs 1+ g (~ 2.6 MeV) 32Cl + p Experimental Goal: Measure excitation energies of the relevant states g (1.359 MeV) Ground state 33Ar

  6. H. Schatz Setup for 34Ar(p,d)33Ar measurement Focal plane:identify 33Ar S800 Spectrometer at NSCL: Beamblocker 33Ar 34Ar 34Ar(p,d)33Ar* Plastictarget 34Ar Radioactive 34Ar beam84 MeV/u T1/2=844 ms(from 150 MeV/u 36Ar) SEGAGe array(14 Detectors)

  7. H. Schatz with experimental data shell model only x 3 uncertainty x10000 uncertainty New 32Cl(p,g)33Ar rate – Clement et al. PRL 92 (2004) 2502 Doppler corrected g-rays in coincidence with 33Ar in S800 focal plane: g-rays from predicted 3.97 MeV state stellar reaction rate reaction rate (cm3/s/mole) 33Ar level energies measured: 3819(4) keV (150 keV below SM) 3456(6) keV (104 keV below SM) temperature (GK) Typical X-ray burst temperatures

  8. H. Schatz Burst peak (~7 GK) Carbon can explodedeep in ocean/crust(but need x10 enhancement)(Cumming & Bildsten 2001) ~ 55% Energy Heavy nuclei in rp-ashes ~ 45% Energy • Disintegration can be main source of energy ! • Increased opacity leads to correct ignition depth crust made of Fe/Ni ? Ashes to ashes – the origin of superbursts ? (Schatz, Bildsten, Cumming, ApJ Lett. 583(2003)L87

  9. H. Schatz r (apid neutron capture) process The r(apid neutron capture) process) What is the origin of about half of elements > Fe(including Gold, Platinum, Silver, Uranium) Abundance Observations Nuclear Physics graph by J. Cowan Supernovae ? n driven wind ? prompt explosions of ONeMg core ? jets ? explosive He burning ? Neutron star mergers ? Nuclear Physics + Abundance Observations  only direct experimental constraint on r-process itself

  10. 78Ni, 79Cu first bottle necks in n-capture flow (80Zn later) 79Cu: half-life measured 188 ms (Kratz et al, 1991) 78Ni : half-life predicted 130 – 480 ms 3 events @ GSI (Bernas et al. 1997) Pt Xe Ni

  11. H. Schatz Some recent r-process motivated experiments ANL/CPT (Cf source) (Clark & Savard et al.)Remeasured masses with high precision ORNL (ISOL)(d,p) and Coulex GSI (in-flight fission)Half-lives, Pn values(Schatz, Santi, Stolz et al.) GSI (in-flight fission) Masses (IMS) (Matos & Scheidenberger et al.) ISOLDE (ISOL)Decay spectroscopy (Dillmann, Kratz et al. 2003) MSU/NSCL (fragmentation) Half-lives, Pn values GANIL (fragmentation) Decay spectroscopy, Sorlin et al. “Fast beam experiments”

  12. H. Schatz First experiment: r-process in the Ni region (Hosmer et al.) • Measure: • b-decay half-lives • Branchings for b-delayed n-emission NSCL Neutron detector NERO 3He + n -> t + p neutron • Detect: • Particle type (TOF, dE, p) • Implantation time and location • b-emission time and location • Neutron-b coincidences R-process Beam Si Stack ~ 100 MeV/u

  13. r-process nuclei 77Ni 78Ni 75Co 73Co 74Co time (ms) Total 78Ni yield: 11 events in 104 h Particle Identification: Energy loss in Si ~ Z Time of flight ~ m/q

  14. H. Schatz Preliminary results Ni half-lives as a function of mass number – comparison with “global” models Half-life (s) 78Ni half-life(11 events) Mass number P. Hosmer

  15. H. Schatz Impact of 78Ni half-life on r-process models  need to readjust r-process model parameters

  16. H. Schatz Known half-life First NSCL experimentscompleted First NSCL experimentscompleted Rare Isotope Accelerator (RIA) • NSCLcovers large fraction of A<130 r-process • big discrepancies among r-process models • possibility of multiple r-processes NSCL and future facilities reach Experimental Nuclear Physics + Observations Experimental test of r-process models is within reach Vision: r-process as precision probe

  17. H. Schatz Conclusions Interesting time in Nuclear Astrophysics where observations and experiments zoom in on most extreme (but common) scenarios Fundamental questions to be answered: The origin of the elements Properties of matter under extreme conditions. • Need a complementary approach to nuclear astrophysics • need a variety of experiment types for a wide range of data • need a variety of facilities (ISOL and fragmentation beams, and stable beams too !) • need experiment and nuclear theory to: • fill in gaps • correct for astrophysical environment • understand nuclear physics A range of nuclei in the r- and rp-process are now accessible at the NSCL Coupled Cyclotron Facility. Need a next generation radioactive beam facilities such as RIA or FAIRto address most of the nuclear physics relevant for astrophysics.  Collaboration

  18. H. Schatz Collaboration Collaborations rp-process r-process Hope College P.A. DeYoung G.F. Peaslee Mainz: O. Arndt K.-L. Kratz B. Pfeiffer MSU: R.R.C. Clement D. Bazin W. Benenson B.A. Brown A.L. Cole M.W. Cooper A. Estrade M.A. Famiano N.H. Frank A. Gade T. Glasmacher P.T. Hosmer W.G. Lynch F. Montes W.F. Mueller P. Santi H. Schatz B.M. Sherrill M.-J. van Goethem M.S. Wallace MSU: P. Hosmer F. Montes R.R.C. Clement A. Estrade S. Liddick P.F. Mantica C. Morton W.F. Mueller M. Ouellette E. Pellegrini P. Santi H. Schatz M. Steiner A. Stolz B.E. Tomlin PNNL P. Reeder Notre Dame: A. Aprahamian A. Woehr Maryland: W.B. Walters

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