Recent developments and new experiments for understanding stellar nucleosynthesis

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1 Recent developments and new experiments for understanding stellar nucleosynthesis Iris Dillmann Helmholtz Young Investigators Group LISA Justus-Liebig Universität Giessen GSI Helmholtzzentrum für Schwerionenforschung

2 Solar Abundances Characteristic isotopic abundances for materials within the solar system also valid outside solar system? ( Galactic abundances?) 16 orders of magnitude How are the isotopes produced? 2

3 Solar abundances of heavy elements Local abundance maxima (and minima) are mirrors of nuclear structure (shell closures, pairing effects) N = N s + N r (+ N p ) N r = N - N s s + r: ~99% of abundances 3

4 The rapid neutron capture process High neutron densities (n n >> cm -3 ) ~1 ms per capture Moderate temperatures (T=1-2 GK) 56 Fe to ~Pu (Z=94, A~260) in few seconds End point: fission barriers (theory!) fission recycling (2x A~130) Astrophysical scenario: still under discussion! Neutron star mergers? Core collapse supernova? 4

5 Input for network calculations During equilibrium phase: Astrophysical parameters Neutron density (n n cm -3 ) Temperature (T> 1 GK) Duration of neutron exposure (few seconds) Half-lives: Shape Masses (S n, Q b ): Path Calculation of progenitor abundances Nuclear physics parameters: Experiments + Theory During Freeze out phase: (n,g)/ (g,n) cross sections b-delayed neutron emission (P n ) Z>80: fission barriers, b-delayed fission, (n,f)-cross sections t 1/2 (a) for A>210 Comparison with solar r abundances 5

6 The modern r process Continuous superposition of many r-process components - T= 1.35 GK (constant) Broad boulevard Strongly dependent on mass models! C. Freiburghaus et al., Ap. J. 516 (1999) 381 H. Schatz et al., Ap. J. 579 (2002) 626 6

7 Goals Measurement of b-decay half-lives b-delayed neutron emission April 5th 2011 I. Dillmann - NPA 5 7

8 GSI Helmholtz Young Investigators Group ( ) Iris Dillmann (Group leader) Michele Marta (Postdoc) Alexey Evdokimov (PhD student) + IONAS and FRS-ESR teams 8

9 b-delayed 1 and 2 neutron emission (P 1n, P 2n ) S n < Q b Important nuclear structure information P n : b-strength above S n t 1/2 ( A Z+1): sensitive to low-lying b-strength From time-dependence of n-emission: t 1/2 ( A Z) S 2n < Q b First experimental identification: - 11 Li (t 1/2 = 8.6 Azuma et al., PRL 43, 1652 (1979) Na (t 1/2 = Detraz et al., Phys. Lett. 94B, 307 (1980) - 98 Rb (t 1/2 = 114 Reeder et al., PRL 47, 483 (1981) Accurate mass measurements needed for predictions! April 5th 2011 I. Dillmann - NPA 5 9

10 b-delayed 1 neutron emission: Theory Agreement (even-odd staggering) K. Langanke, G. Martínez-Pinedo, Rev. Mod. Phys. 75, (2003) 819 Need experiments to set constraints on theoretical predictions 10

11 Astrophysical influence of P 1n and P 2n During Freeze-out : detour of b-decay chains solar r-abundance changes QRPA (GT+ff) predictions: b-decay: 6.9% P(1n): 6.5 % P(2n): 86.7% In ms bn, b2n April 5th 2011 I. Dillmann - NPA 5 11

12 Predictions and status of P(xn) around N=82 QRPA predictions (GT+ff) t 1/2 measured identified Overall fair agreement of P(1n), but not enough data yet Candidates for b2n emitters: 134,135 In, 135,137 Sn, 136 Sb Candidate for b3n emitters: 135 In (P(3n)= 7.3%) P. Möller et al., PRC 67, (2003) April 5th 2011 I. Dillmann - NPA 5 12

13 Status bdn Only 1 measurement for A>150: P n = ( ) % Validation missing G. Stetter, Nucl. Sci. Abstr. 16, 1409, Abstr (1962) bdn evaluation/ compilation: B. Pfeiffer et al., arxiv:nucl-ex/ April 5th 2011 I. Dillmann - NPA 5 13

14 Half-life predictions Discrepancy between models: factor 10! Experimental data required K. Langanke, G. Martínez-Pinedo, Rev. Mod. Phys. 75, (2003)

15 Status t 1/2 : QRPA(GT+ff) vs. Exp. around N=82 Pd Ag Ag, Sn: Good agreement (factor 2) Pd: Exp. factor 5 lower Cd: Exp. factor 5-10 lower Cd ( ) In In: Exp. factor 3 higher Sb, Sn: trend changes beyond N=82! Measurements important to set constraints on models! Sn Sb P. Möller et al., PRC 67, (2003) April 5th 2011 I. Dillmann - NPA 5 15

16 The Fragment Separator (FRS) Achromatic high resolution magnet spectrometer Length (Target- S4): 73 m Br= 5-18 Tm 4x 30 dipoles (H-type, 1.6 T) + quadrupoles In-flight separation: Bρ- E-Bρ technique (Degrader at S2) Isotopically pure beam possible Thick target (Pb, Be): fission/fragmentation D1 D4 D3 Typical beams for neutron-rich isotopes: 238 U, 208 Pb, 197 Au, 136 Xe D2 Cocktail beams: 2 approved experiments (Aug/Sep 2011) - neutron-rich Rh, Pd, Ag (N~82) - neutron-rich Ir, Pt, Au, Hg, Tl (N>126) April 5th 2011 I. Dillmann - NPA 5 16

17 SIMBA + S4 BEta delayed Neutron detector Fragments from FRS Silicon IMplantation detector and Beta Absorber Dt (b-n)~ 200 ms 2 experiments planned for 2011 Collaboration with MSU/NSCL, TUM, Barcelona/Valencia/Madrid 17

18 DETECTION EFFICIENCY [%] BEta delayed Neutron detector 30 counters 20 counters NEUTRON ENERGY [MeV] 20 3 He counters (20 atm) He counters (10 atm) BELEN-30 (2011) ca. 1t PE Value of 3 He: 625 k$ (worldwide shortage) M.B. Gómez Hornillos et al., Proc. Int. Conf. on Nucl. Data for Science and Techn. (2010) 18

19 N=82: Status I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb N=82 GSI proposal April 5th 2011 I. Dillmann - NPA 5 19

20 N=126: Status GSI proposal Will be heaviest bdn-emitters measured so far Last known: 175 Er (19 n less), 177 Tm (18 n less) Maximum at N=126: 194 Er, 195 Tm still long way to go but... April 5th 2011 I. Dillmann - NPA 5 20

21 Measurements in the ESR (or CR) Fully ionized ions inserted into ESR Half-lives ~ ms no e - cooling possible! Few (<10) mother ions A Z circulating (500 ns/turn) b-decay to A Z+1 and/ or bdn to A-1 Z+1 M Db Dbn Position-sensitive detectors ESR acceptance 1.5% If decay happens in straight section: deflection in next dipole Identification: Schottky pickups Collaboration with 21

22 CR68: new layout (increased circumference) Schottky Circumference = m, Br max =13 Tm magnet stoch. cooling pick-up/kicker inj./extr. kicker RF cavity detectors / beam diagnostics valves ToF-1 pocket ToF-2 A. Dolinskii

23 Stellar lifetimes Crab nebula Remnant of the Supernova 1054 Distance: ~1.9 kpc SN 1054 visible 23 days and 653 nights g-ray astronomy: Observation of ongoing nucleosynthesis SN isotopes: t 1/2 = few weeks 10 6 y T up to 7 GK: fully ionized nuclei Later: cooling and recombination 23

24 Influence of stellar plasma on lifetimes Decay influenced by temperature (ionization and nuclear excitation) electron and positron density (free electron/positron capture) Terrestrial conditions Orbital-EC b + -decay (Q>1.022 MeV) (Continuum-state) b - -decay a-decay Ground- or isomeric state decays Stellar conditions Fully ionized: stable (no EC) Orbital-EC (longer t 1/2 ) b + -decay (Free) EC Continuum-state b-decay Bound-state b-decay (Q+B e ): shorter t 1/2 (Free) positron capture No e - screening: Coulomb-barrier enhanced, longer t 1/2 Decays also from excited states (faster) 24

25 (Some) astrophysical case studies Bound-state b-decay (shorter t 1/2 ) 47 d 33 a 255 s M. Jung et al., PRL 69, 2164 (1992). F. Bosch et al., PRL 77, 5190 (1996). T. Ohtsubo et al., PRL 95, (2005). Electron capture X Z+ : stable X (Z-1)+ : t 1/2 *2 X (Z-2)+ : t 1/2 *9/ a b - decay + EC t 1/2 (500 MK, b - )= t 1/2 (500 MK, EC)= 32.2 d 1438 d 0.08 d 58 d 7 d 2.6*10 5 d 25

26 44 Ti from SN: why only few sources? Cas A SN remnant (SN ~1680, SN IIb?) Vela SN remnant (SN 12 ky ago) 44 Ti model yields 60.4 a Ia: ( )*10-6 M Ibc: (3-9)*10-5 M II: dep. on stellar mass 26

27 44 Ti from SN: why only few sources? 44 Ti line flux: Yield in 10-4 M Lifetime of 44 Ti Distance in kpc Cassiopeia A Meas. flux: (2.5 ±0.5)*10-5 g cm -2 s -1 Age of SN: t~ 320 y t 1/2 = 60.4 y Distance: 3.4 kpc Yield( 44 Ti)= ( )*10-4 M Model yields lower than measured (factor 3) Can 44 Ti be ejected? (Mass cut, show 3D simulations same effect?) Wrong input parameters (stellar lifetime)? F. Timmes et al., Astrophys. J. 449, 204 (1995) 27

28 How can higher results explained? longer if highly ionized Evolution of SN remnants 1) Free expansion ( y): a: 44 Ti fully ionized during explosion, recombination neutral after ~1000s; b: re-ionization by reverse shock (up to 50 MK) 2) Sedov-Taylor phase (~10 4 y): adiabatic expansion 3) Snow plough phase (~10 9 y): radiative cooling 4) Merging with ISM Time- and position-dependence 10 ly Chandra X-ray observatory Model yields can be higher by ~factor 3 Y. Motizuki et al., Astr. Astroph. 346, 831 (1999) Uncertainties: (Exact) thermodynamic history of SN remant unknown 28

29 Outlook: Measure stellar t 1/2 in the ESR b+ b- Same principle as for bound-state b-decay measurements High production rates needed (>10 7 pps) Electron cooling Schottky pickups Lifetimes < ESR lifetimes (recombination, losses) EC daughter: in ring, b - /b + daughters with pocket detectors Picture: Y. A. Litvinov 29

30 Summary 1 Planned to get for the first time experimental t 1/2 of 121,122 Rh, 125 Pd I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb N=82 GSI proposal April 5th 2011 I. Dillmann - NPA 5 30

31 Summary 2 GSI proposal First experimental information on 205,206 Ir, 208,209 Pt, Au, Hg, Tl Will be heaviest bdn-emitters measured so far Future: measure P 2n and P 3n emitters (good candidates: 134,135 In) Proof of principle: measure P n in the storage ring (ESR, CR) still long way to go but... April 5th 2011 I. Dillmann - NPA 5 31

32 (Exciting) Outlook stable nuclei nuclides with known masses G.Audi et al., Nucl. Phys. A729 (2003) 3 to be measured with SUPER-FRS-CR-RESR-NESR Conceptual Design Report, GSI 2001 observed nuclei 82 Investigation of Lifetimes and Masses 126 r-process path NUSTAR collaboration: 32

33 The S323-S410 Collaboration IFIC Valencia Jose Luis Tain (spokesperson S410) Alejandro Algora Cesar Domingo Pardo Jorge Agrarmunt MSU/ Notre Dame Fernando Montes (spokesperson S323) Karl Smith (PhD) Hendrik Schatz UPC Barcelona Belen Gomez Hornillos Roger Caballero (PhD) Anuj Parikh TU München Thomas Faestermann Roman Gernhäuser Christoph Hinke Konrad Steiger GSI Darmstadt Iris Dillmann Chiara Nociforo and the FRS-team Daniel Cano Ott Daniel Galaviz Redondo (Lisbon) Trino Martinez (Madrid)...and many more... April 5th 2011 I. Dillmann - NPA 5 33