1. 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

2. 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

3. 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

4. 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

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

6. 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
Azuma et al., PRL 43, 1652 (1979)
Na (t1/2=
Detraz et al., Phys. Lett. 94B, 307 (1980)
- 98Rb (t1/2= Reeder et al., PRL 47, 483 (1981)
► Accurate mass measurements needed for predictions!
April 5th 2011
I. Dillmann - NPA 5

7. 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

8. 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, (2003)
April 5th 2011
I. Dillmann - NPA 5

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

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

11. 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, (2003)
April 5th 2011
I. Dillmann - NPA 5

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

13. The Fragment Separator (FRS)
Achromatic high resolution magnet spectrometer
Length (Target- S4): 73 m
Br= 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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