The r process: Towards the (experimental) terra incognita Iris Dillmann for the S323-S410 Collaboration Helmholtz Young Investigators Group "LISA- Lifetime Spectroscopy for Astrophysics" Justus-Liebig Universität Giessen GSI Helmholtzzentrum für Schwerionenforschung

Solar Abundances: Synthesis beyond Iron B2FH (1957) N=50 N=82 N=126 N=50 Z=50 N=82 N = Ns + Nr + Np Local abundance maxima (and minima) are mirrors of nuclear structure (shell closures, pairing effects...) ~50% ~50% ~1% April 5th 2011 I. Dillmann - NPA 5

The „rapid neutron capture process“ Nr = N - Ns High neutron densities (nn>> 1020 cm-3)  ~1 ms per capture “Moderate” temperatures (T=1-2 GK)  56Fe to ~Pu (Z=94, A~260) in few seconds End point: fission barriers (theory!)  “fission recycling” (2x A~130) Astrophysical scenario: Neutron star mergers? Core collapse supernova ? April 5th 2011 I. Dillmann - NPA 5 3

Input for network calculations During equilibrium phase: Astrophysical parameters Neutron density (nn≥ 1020 cm-3) Temperature (T> 1 GK) Duration of neutron exposure (few seconds) Calculation of progenitor abundances Nuclear physics parameters: Experiments + Theory Half-lives: Shape Masses (Sn, Q): Path During “Freeze out” phase: (n,g)/ (g,n) cross sections b-delayed neutron emission (Pn) Z>80: fission barriers, b-delayed fission, (n,f)-cross sections t1/2(a) for A>210 Comparison with solar r abundances April 5th 2011 I. Dillmann - NPA 5

Goals S323/S410@ Measurement of b-decay half-lives b-delayed neutron emission S323/S410@ April 5th 2011 I. Dillmann - NPA 5

b-delayed 1 and 2 neutron emission (P1n, P2n) Sn< Qb Important nuclear structure information Pn : b-strength above Sn t1/2(AZ+1): sensitive to low-lying b-strength From time-dependence of n-emission: t1/2(AZ) S2n < Qb First experimental identification: - 11Li (t1/2= 8.6 ms) @ISOLDE: Azuma et al., PRL 43, 1652 (1979) - 30-32Na (t1/2= 13-48 ms) @ISOLDE: Detraz et al., Phys. Lett. 94B, 307 (1980) - 98Rb (t1/2= 114 ms) @TRISTAN: Reeder et al., PRL 47, 483 (1981) ► Accurate mass measurements needed for predictions! April 5th 2011 I. Dillmann - NPA 5

Astrophysical influence of P1n and P2n 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 134 138 ms bn, b2n April 5th 2011 I. Dillmann - NPA 5

Predictions and status of P(xn) around N=82 QRPA predictions (GT+ff) t1/2 measured identified Overall fair agreement of P(1n), but not enough data yet Candidates for b2n emitters: 134,135In, 135,137Sn, 136Sb Candidate for b3n emitters: 135In (P(3n)= 7.3%) P. Möller et al., PRC 67, 055802 (2003) April 5th 2011 I. Dillmann - NPA 5

G. Stetter, Nucl. Sci. Abstr. 16, 1409, Abstr.10963 (1962) Status bdn Pn= 0.007 (+0.007 -0.004) % Validation missing G. Stetter, Nucl. Sci. Abstr. 16, 1409, Abstr.10963 (1962) Only 1 measurement for A>150: bdn evaluation/ compilation: B. Pfeiffer et al., arXiv:nucl-ex/0106020 April 5th 2011 I. Dillmann - NPA 5

The r process: Experimental status (t1/2) Mirror of nuclear structure far off stability Terra incognita April 5th 2011 I. Dillmann - NPA 5

Status t1/2: QRPA(GT+ff) vs. Exp. around N=82   Ag, Sn: Good agreement (factor 2) Pd: Exp. factor 5 lower Cd: Exp. factor 5-10 lower In: Exp. factor 3 higher Pd Ag  Cd () In Sb, Sn: trend changes beyond N=82! Measurements important to set constraints on models!   Sn Sb P. Möller et al., PRC 67, 055802 (2003) April 5th 2011 I. Dillmann - NPA 5

The GSI facility Measuring position April 5th 2011 I. Dillmann - NPA 5

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 D4 D1 D3 Cocktail beams: Typical beams for neutron-rich isotopes: 238U, 208Pb, 197Au, 136Xe D2 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

Silicon IMplantation detector and Beta Absorber SIMBA Constructed and developed at • 1 x- and 1 y-detector, 60x segmented each 2 SSSSD, 7x segmented in x 3 DSSSD (implantation area): 60x segmented in x, 40x in y-direction PhD thesis C. Hinke, TUM (2010) Diploma thesis K. Steiger, TUM (2009) Pictures: K. Steiger April 5th 2011 I. Dillmann - NPA 5

BEta deLayEd Neutron detector (BELEN-30) Universidad Politecnica de Cataluna, Barcelona IFIC Valencia CIEMAT Madrid 20 counters 30 counters NEUTRON ENERGY [MeV] DETECTION EFFICIENCY [%] High pressure 3He long counters PE matrix, size ~ 1m3 M.B. Gómez Hornillos et al., Proc. Int. Conf. on Nucl. Data for Science and Techn. (2010) April 5th 2011 I. Dillmann - NPA 5

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

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

Exiting Outlook BELEN setup could be one of the nuclides with known masses G.Audi et al., Nucl. Phys. A729 (2003) 3 stable nuclei to be measured with SUPER-FRS-CR-RESR-NESR Conceptual Design Report, GSI 2001 observed nuclei 82 r-process Investigation of Lifetimes and Masses path 126 50 82 28 20 50 BELEN setup could be one of the first setups for measurements after completion of first Super-FRS stage 8 28 20 8 April 5th 2011 I. Dillmann - NPA 5

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

Half-life predictions Discrepancy between models: factor 10! Experimental data required K. Langanke, G. Martínez-Pinedo, Rev. Mod. Phys. 75, (2003) 819 April 5th 2011 I. Dillmann - NPA 5