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: roger.caballero@upc.edu

S410 experiment collaboration