EuroGenesis Workshop. Barcelona 2013Barcelona 2013

Measurements of β-delayedMeasurements of β delayedneutron emission aroundneutron emission aroundthe third r-process peak

ROGER CABALLERO-FOLCH (DFEN –UPC)

p p( )

& S410 experiment collaborationBarcelona, 14 de juny de 2013

Contents

Astrophysics motivation

Contents

op y o a o

Experimental setup at GSI-FRS facility

Ongoing analysis and preliminary results

Detection System: SIMBA & BELEN detector

Ongoing analysis and preliminary results

Future measurements: BRIKEN

Summary and outlook

slide 1 of 17

Motivation: nucleosynthesis beyond Fe in the r-process path

Goal: Experimental determination of half lives and neutron branchings of several exotic nuclei in the neutron rich region beyond N=126

Regionof

interesti thiin thisstudy

The Astr. Jour., 579  (2002), H. Schatz et al. Proc. CGS‐13 (2009), G. Martinez‐Pinedo

Neutron number N

Understanding of A=195 peak in the r-process abundance pattern.

Neutron number N

R-process calculations rely on theoretical predictions (QRPA & FRDM), R process calculations rely on theoretical predictions (QRPA & FRDM), with remarkable discrepancies and large uncertainties.

slide 2 of 17

Nuclear data for the Pt-peak formation: half-lives

N=126N 126

known t1/2

t1/2 x 0.11/2

NPA VI, Lisbon, 20-24 May 2013Slide 3 of 17C.Domingo-Pardo Priv. Com.

Experiment at GSI – FRS facility. 238U fragmentation beam.

9 238Large intensity (2x109 ions/pulse) & high-energy (1 GeV/u) for 238U beams

SIMBA +BELEN

Tracking detectors: particle ID on anTracking detectors: particle ID on anevent-by-event basis.SIMBA: Implats & β decaysBELEN: Neutrons

The detection system is based on a stack of SSSD- and DSSD-detectors for measuring ion-implants and beta-decays (SIMBA) Implants-region was

BELEN: Neutrons

measuring ion-implants and beta-decays (SIMBA). Implants-region was surrounded by the 4π neutron detector BELEN.

slide 4 of 17

Implantation, β decay & neutron detection: SIMBA + BELEN

Silicon striped detectors (SSSD’s and DSSD’s)

Beam

Tracking: (X,Y) Implants

- absorber - absorberImplantationarea( ) p

PhD thesis C. Hinke, TUM (2010) Diploma thesis K. Steiger, TUM (2009)

BELEN efficiency was

about 40% about 40% (checked

experimentally)

The Beta dELayEd Neutron (BELEN) detector, based in 3He counters b dd d i l th l t i l t d d Sili IM l t tiembedded in a polyethylene matrix, located around Silicon IMplantation

Beta Absorber (SIMBA).slide 5 of 17

Neutron detection 3He counters as detector

Th d t ti f th t i b d i di t th d th d t ti 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 keVHe + n H + H + 765 keV

Other reactions:10B + n → 7Li* + 4He + 2310 keV7Li* → 7Li + 480 keVn

Polyethylenemoderator Li Li 480 keV

I b

n

n

n

Proportional

Noise

Neutron signal

Ion beam n 3He counterSiliconβ decay detector

eut o s g a

slide 6 of 17

Tests and experiments with BELEN detector

GSI:S410 “Measurement of β-delayed neutrons around the 3rd r-process peak” C. Domingo-Pardo et alPardo et al.PERFORMED, September 2011

GSI: S323 “Beta‐decay of very neutron‐rich Rh, Pd, Ag nuclei including the r‐

iti i tprocess waiting point 128Pd”. F. Montes et al.PERFORMED, September 2011

Z=28, N=50;

JYFL (2009, 2010 & 2013)I162 “D l d t t f d d t

Z=50, N=82

I162 “Delayed neutron measurements for advanced reactor technologies and astrophysics” JL Taín JYFL. Expected 2013B.Gomez-Hornillos et al. NIM in progress (2009 exp)

Neutron number NBackground measurements at GSI (2010) and LSC Canfranc (2011) D.Jordan et al. Astr.Phys Vol.42, Feb 2013, p.1–6

slide 7 of 17

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 17

Good statistics implantation for 208-211Hg, 211-215Tl and 214-218Pb

214-218Pb211-215Tl 214-218Pb

208-211Hg

I l t th hi h t d l f SIMBA d t tImplants on the high segmented layers of SIMBA detector

slide 9 of 17

Data available and data expected to obtain

Implanted in ROI with enough statistics:208-211Hg, 211-215Tl,214-218Pbg, ,

Other implants of 212-213Hg, 216Tl, 219Pb, and 202-204Pt,203-208Au, 217-221Bi

214-215/216-218Pb211-213/214-215Tl

208-209/210-211Hg

Possible evaluation of more nuclei implanted implanted in other layers.

slide 10 of 17

http://www.nndc.bnl.gov- - - G.Benzoni-A.I.Morales et al, Ph.Lett.B 715 (2012)

PRELIMINARY results for half lives

209Hg 211Tl Integral 398

T1/2 = 59.56 s (21.91) T1/2 = 73.49 s (30.25)1/2 ( ) 1/2 ( )

G.Benzoni et al. PLB 715 (2012) t1/2 = 88 (+46-29) s

t1/2 = 36.5(+/-7.5) s

212Tl 213Tl

T1/2 = 75.00 s (33.51) T1/2 = 58.30 s (29.35)

G.Benzoni et al. PLB 715 (2012) t1/2 = 96 (+42-38) s

slide 11 of 17

Nuclear data for the Pt-peak formation: half-lives

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 neighbourhoodOnly possibility is to benchmark the performance of models in the neighbourhood

N = 126

It seems that nuclear models tend to overestimate the b decay half live at

T. Kurtukian-Nieto et al., arXiv:0711.0101v1J.Benlliure et al. NPA-V, 2012

G.Benzoni et al., Phys.Lett. B 715 (2012)

It seems that nuclear models tend to overestimate the b-decay half-live at N126…

slide 12 of 17

PRELIMINARY neutron correlations

209Hg 211Tl Integral 398209Hg 211Tl

Integral 10

Integral 398

212Tl 213Tl

Integral 12

(Effi i 40%)

NN

P nn

n1

(Efficiency ~40%)

slide 13 of 17

Nuclear data for the Pt-peak formation: b-neutrons

Beta-delayed neutron emission has a twofold impact in the nucleosynthesis:• It enhances the neutron density of the environment after freeze-out (re-activation).• It shifts the abundances towards lower masses (Pn: A A-1, P2n: A A-2, etc)etc).

known t1/2 Only oneknown t1/2

known Pn

yexperimental valueis known:Tl-210 ! !

• A V Kogan et al Sov Phys203Ir • A.V.Kogan, et al. Sov. Phys.

JETP 5(1957) 365• G.Stetter, TID-14880(1961)exp. known Pn’s

Q – Sn > 0

QSn

A N Z A N 1 Z 1 A 1 N 2 Z 1A,N,Z A,N-1,Z+1 A-1,N-2,Z+1A,N,Z A,N-1,Z+1 A-1,N-2,Z+1

slide 14 of 17

Future plans: improved detectors + larger RIB intensities

New campaign for the measurement of -delayed neutrons at RIKEN:

Large need of b delayed

New campaign for the measurement of -delayed neutrons at RIKEN:

Large need of b-delayedneutron emissionmeasurements!!!

??

BRIKENBRIKEN CampaignCampaign:BRIKEN BRIKEN CampaignCampaign: Opportunities with the BELEN neutron

detector at RIKEN

slide 15 of 17

Future plans: improved detectors + larger RIB intensities

EfficiencyEfficiency > 50%> 50%

2nd BRIKEN WORKSHOP: 30-31 Julyat RIKEN

Collaborators are welcome to join!!!Collaborators are welcome to join!!!

slide 16 of 17

Summary and outlookSummary 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=126identified in the Hg/Tl/Pb region, beyond the shell closure N=126.

-Preliminary half-lives have been obtained by implant-beta correlation

method with DSSD detectors. They must be rechecked with other

numerical methods.

- 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.y β y p g g

-We plan to measure a large amount of neutron-rich nuclei in a

campaign at the RIB facility of RIKEN (Japan)campaign at the RIB facility of RIKEN (Japan).

slide 17 of 17

Universitat Politècnica de Catalunya (UPC)

S410 experiment collaboration

y ( )

Institut de Física Corpuscular de València (IFIC)

Helmholtzzentrum für Schwerionenforschung GmbH

(GSI)(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)( g )

School of Physics & Astronomy, U. Edinburgh (UK)

Department of Physics, University of Liverpool (UK)

STFC Daresbury Laboratory (UK)STFC, Daresbury Laboratory (UK)

Laboratori Nazionali di Legnaro, INFN (Italy)

Flerov Laboratory, JINR, Dubna (Russia)

CENBG, Université Bordeaux (France)

et al.Contact: roger.caballero@upc.edu

Work supported by the Spanish Ministry of

Economy and Competitivity under contract

FPA 2011-28770-C03-03