Measurements of β-delayeddelayed neutronemissionaround ...Other implants of 212-213Hg, 216Tl,...
Transcript of Measurements of β-delayeddelayed neutronemissionaround ...Other implants of 212-213Hg, 216Tl,...
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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
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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
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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.
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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.
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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.
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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
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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
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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
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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.
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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
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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.
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http://www.nndc.bnl.gov- - - G.Benzoni-A.I.Morales et al, Ph.Lett.B 715 (2012)
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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
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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…
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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%)
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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
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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
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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!!!
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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).
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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: [email protected]
Work supported by the Spanish Ministry of
Economy and Competitivity under contract
FPA 2011-28770-C03-03