Roger Caballero-Folch (DFEN –UPC)València, 15 de juliol de 2013
β-decay half-lives and β-delayed neutron emission
measurements for r-process nucleosynthesis
S410 experiment collaboration:R. Caballero-Folch, C. Domingo-Pardo, G. Cortes, J.L. Taín, J. Agramunt, A. Algora, F. Ameil, Y. Ayyad, J. Benlliure, M. Bowry, F. Calviño, D. Cano-Ott, T. Davinson, I. Dillmann, A. Estrade, A. Evdokimov, T. Faestermann, F. Farinon, D. Galaviz, A. García-Ríos, H. Geissel, W. Gelletly, R. Gernhäuser, M.B. Gomez-Hornillos, C. Guerrero, M. Heil, C. Hinke, R. Knöbel, I. Kojouharov, J. Kurcewicz, N. Kurz, Y. Litvinov, L. Maier, J. Marganiec, M. Marta, T. Martnez, F. Montes, I. Mukha, D.R. Napoli, C. Nociforo, C. Paradela, S. Pietri, Zs. Podolyak, A. Prochazka, S. Rice, A. Riego, B. Rubio, H. Schaner, C. Scheidenberger, K. Smith, E. Sokol, K. Steiger, B. Sun, M. Takechi, D. Testov, H. Weick, E. Wilson, J.S. Wineld, R. Wood, P. Woods, and A. Yeremin.
Astrophysics motivation
Contents
Ongoing analysis and preliminary results
slide 1 of 14
Experimental setup at GSI-FRS facility
Summary and outlook
Detection System: SIMBA & BELEN detector
Motivation: nucleosynthesis beyond Fe in the r-process path
Understanding of A=195 peak in the r-process abundance pattern.
The Astr. Jour., 579 (2002), H. Schatz et al. Proc. CGS-13 (2009), G. Martinez-Pinedo
Neutron number N
Region of
interest in this study
R-process calculations rely on theoretical predictions (QRPA & FRDM), with remarkable discrepancies and large uncertainties far of stability.
Goal: Experimental determination of half lives and neutron branchings of several exotic nuclei in the neutron rich region beyond N=126
slide 2 of 14
t1/2 x 0.1
Nuclear data for the Pt-peak formation: half-lives
NPA VI, Lisbon, 20-24 May 2013
N=126
known t1/2
Slide 3 of 14
FRDM Model
Experiment at GSI – FRS facility. 238U fragmentation beam.
Large intensity (2x109 ions/pulse) & high-energy (1 GeV/u) for 238U beams
The detection system is based on a stack of SSSD- and DSSD-detectors for measuring ion-implants and beta-decays (SIMBA). Implants-region was surrounded by the 4π neutron detector BELEN.
SIMBA +BELEN
Tracking detectors: particle ID on an event-by-event basis.SIMBA: Implats & β decaysBELEN: Neutrons
slide 4 of 14
Plenary talk K-H Langanke
Implantation, β decay & neutron detection: SIMBA + BELEN
The Beta dELayEd Neutron (BELEN) detector, based in 3He counters embedded in a polyethylene matrix, located around Silicon IMplantation Beta Absorber (SIMBA).
Tracking: (X,Y) Implants
b- absorber b- absorber
Beam
Implantation area
PhD thesis C. Hinke, TUM (2010) Diploma thesis K. Steiger, TUM (2009)
BELEN efficiency was
about 40% (checked
experimentally)
slide 5 of 14
Silicon striped detectors (SSSD’s and DSSD’s)
Noise
Neutron signal
Neutron detection 3He counters as detector
The detection of the neutron is based on an indirect method: the detection of
the products of the reaction of the neutron with 3He counters:
3He + n 3H + 1H + 765 keVOther reactions:
10B + n → 7Li* + 4He + 2310 keV
7Li* → 7Li + 480 keV
Ion beam
n
n
n
Polyethylenemoderator
Proportional 3He counter
Silicon
β decay detector
slide 6 of 14
Tests and experiments with BELEN detector
Neutron number N
GSI:S410 “Measurement of β-delayed neutrons around the 3rd r-process peak” C. Domingo-Pardo et al.PERFORMED, September 2011
GSI: S323 “Beta-decay of very neutron-rich Rh, Pd, Ag nuclei including the r-process waiting point 128Pd”. F. Montes et al.PERFORMED, September 2011
Z=28, N=50;
JYFL (2009, 2010 & 2013)I162 “Delayed neutron measurements for advanced reactor technologies and astrophysics” JL Taín JYFL. Expected 2013B.Gomez-Hornillos et al. NIM in progress (2009 exp)
Z=50, N=82
Background measurements at GSI (2010) and LSC Canfranc (2011) D.Jordan et al. Astr.Phys Vol.42, Feb 2013, p.1–6
slide 7 of 14
Isotopes of Pt, Au, Hg, Tl, Pb, Bi, Po, At, Rn and Fr identified
Isomer tagging was used for Z identification and two centred settings on
211Hg and 215Tl were measured during 4.5 days. The implantation area
was optimized for Hg and Tl region where good resolution has been
obtained.
slide 8 of 14
Isotopes of Pt, Au, Hg, Tl, Pb, Bi, Po, At, Rn and Fr identified
Isomer tagging was used for Z identification and two centred settings on
211Hg and 215Tl were measured during 4.5 days. The implantation area
was optimized for Hg and Tl region where good resolution has been
obtained.
slide 8 of 14
Good statistics implantation for 208-211Hg, 211-215Tl and 214-218Pb
Implants on the high segmented layers of SIMBA detector
slide 9 of 14
Data available and data expected to obtain
slide 10 of 14
http://www.nndc.bnl.gov 209Hg t1/2 = 36.5(+/-7.5) s G.Benzoni-A.I.Morales et al, Ph.Lett.B 715 (2012)211Tl t1/2 = 88 (+46
-29) s212Tl t1/2 = 96 (+42
-38) s
Possible evaluation of more nuclei implanted implanted in other layers.
211-213/214-215Tl
Implanted in ROI with enough statistics:
208-211Hg, 211-215Tl,214-218Pb
Other implants of 212-213Hg, 216Tl, 219Pb, and 202-204Pt, 203-
208Au, 217-221Bi
208-209/210-211Hg
214-215/216-218Pb
Nuclear data for the Pt-peak formation: state of the art
How theoretical models compare with experiment?
• No experimental information along N=126 region nuclei
• Only possibility is to benchmark the performance of models in the neighbourhood
It seems that nuclear models tend to overestimate the b-decay half-live at N<126 and to underestimate it for N>126…
T. Kurtukian-Nieto et al., arXiv:0711.0101v1J.Benlliure et al. NPA-V, 2012
G.Benzoni et al., Phys.Lett. B 715 (2012)
N = 126
slide 12 of 14
Implant – beta correlation studies
slide 11 of 14
Several methods of analysis for implant-beta correlation are being performed due to the complex background and statistics.
slide 13 of 14
PRELIMINARY implant – beta - neutron correlations
209Hg
BELEN Efficiency ~40%
slide 13 of 14
PRELIMINARY implant – beta - neutron correlations
211Tl
Integral 10
BELEN Efficiency ~40%
slide 13 of 14
PRELIMINARY implant – beta - neutron correlations
212Tl
Integral 24
BELEN Efficiency ~40%
slide 13 of 14
PRELIMINARY implant – beta - neutron correlations
213Tl
Integral 12
BELEN Efficiency ~40%
Summary and outlook
- Several species of neutron rich heavy nuclei have been produced and
identified in the Hg/Tl/Pb region, beyond the shell closure N=126.
- Correlation methods in order to obtain the half-lives are being studied
by implant-beta analysis of signals at DSSD detectors with numerical
methods and specific techniques.
- In order to obtain final results, we need to improve several aspects in
our data-analysis (simulation, statistical comparator, spatial
correlations, time-correlations, etc).
- The analysis of β-delayed neutron emission probabilities is
ongoing.
- We plan to measure a large amount of neutron-rich nuclei in a
campaign at the RIB facility of RIKEN (Japan).
slide 14 of 14
Universitat Politècnica de Catalunya (UPC)
Institut de Física Corpuscular de València (IFIC)
Helmholtzzentrum für Schwerionenforschung GmbH
(GSI)
NSCL, Michigan State University (MSU-USA)
CIEMAT (Madrid)
Universidade de Santigo de Compostela (USC)
Department of Physics, University of Surrey (UK)
CFNUL Universidade de Lisboa (Portugal)
School of Physics & Astronomy, U. Edinburgh (UK)
Department of Physics, University of Liverpool (UK)
STFC, Daresbury Laboratory (UK)
Laboratori Nazionali di Legnaro, INFN (Italy)
Flerov Laboratory, JINR, Dubna (Russia)
CENBG, Université Bordeaux (France)
et al.
Work supported by the Spanish Ministry of
Economy and Competitivity under contract
FPA 2011-28770-C03-03
Contact: [email protected]
S410 experiment collaboration
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