Diapositiva 1

Measurement of -delayed neutrons around the third r-process peak at GSI

ROGER CABALLERO FOLCH,Barcelona, 9th November 2011Introduction: Theoretical conceptsExperiment proposalGSI facility and experimental setupPreliminary analysisContents

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GSI facility & setupPreliminary analysisIntroductionProposal

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UPC Neutron detector (Beta delayed neutron, BELEN) GSI facility & setupPreliminary analysisIntroductionProposalIntroductionNeutron detector designed and constructed by UPC GRETER research group.The detection of the neutron is based on the detection of products of the following reaction of the neutron with 3He countersIon beamnnnPolyethylenemoderatorProportional 3He counterSilicon decay detector3He + n 3H + 1H + 765 keV

Spectra obtained for each 3He counterEdge effect191 keVFull energy deposited 765 keVNoise

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Neutron emission after - decay scheme GSI facility & setupPreliminary analysisIntroductionProposalIntroductionTo measure neutron emission probabilities after beta decay of neutron rich isotopes with relevance in basic nuclear physics, astrophysics and nuclear technology.

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neutronBETA

Example of -delayed neutron emissionGSI facility & setupPreliminary analysisIntroductionProposalIntroduction

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Nuclear structure knowledge: study different aspects of the decay of these nuclei. Half lives and neutron emission probabilities provide information about their decay mechanism and structure.RelevanceAstrophysics (r-process): - decay studies near the r-process path. Pn values, together with decay half lives, are the main ingredients for the study of heavy elements nucleosynthesis via the r-process. The exact place for the r-process has not been identified yet. GSI facility & setupPreliminary analysisIntroductionProposalIntroduction

S410: Beta-decay measurements of new isotopes near the third r-process peak

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Has been performed at GSI in September 2011 with a week beam time.To measure half lives and beta delayed neutron emission probability of isotopes near the third abundance peak of the r-process (N126).

The measurements were centered on isotopes 215Tl, 211Hg. Some isotopes around have already been identified.

We expect to identify 211-214Hg208-211Au208,209Pt205,206IrExperiment objectivesGSI facility & setupPreliminary analysisIntroductionProposalProposalIntroduction213-216Tl

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GSI facility & setupPreliminary analysisIntroductionProposalProposalStatus of the art

N=126t1/2 existsidentifiedArea of interestPn (%) QRPABn= 2-3 MeVCentered

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GSI facility & setupPreliminary analysisIntroductionProposalProposalExplosive nucleosynthesis and the r-process around the third abundance peak

Effect of half-livesThe Astr. Jour., 579 (2002), H. Schatz et al. Proc. CGS-13 (2009), G. Martinez-PinedoIgnorance-CurveFocus of present proposalr-path

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Difficult to calculate/predict half-live and Pn-values of the nuclei in this region:(I.Borzov, et al. 2003)

FRDM + QRPAK.-L. Kratz, (private communication)

T. Kurtukian-Nieto, et al., Phys. Lett. B (Submitted)K.-L. Kratz, (private communication)

DF3 + QRPA+ FRDM + QRPAExp. T. Kurtukian et al.(P.Moeller, et al. 2003)GSI facility & setupPreliminary analysisIntroductionProposalProposal

GSI facility. Fragment separator spectrometer (FRS)11/16

GSI facility & setupPreliminary analysisIntroductionProposalGSI facility & setupBeam characteristics

238U beam 1GeV/n2x109 ions/s intensity1.6 g/cm2 Be targetProposal

S410 experiment setup

12/16Neutron detectorSIMBAPolyethylene shieldingGSI facility & setupPreliminary analysisIntroductionProposalGSI facility & setup

S410 experiment setup

12/16GSI facility & setupPreliminary analysisIntroductionProposalGSI facility & setup

BELEN neutron detector Neutron shielding FRS detectors

SIMBA detectorSilicon Implantation Detector and Beta Absorber (SIMBA)Multilayer silicon detector

It allowed us to measure both ion implants and -decays.

Decay events can be correlated in time with the detection of neutrons.

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GSI facility & setupPreliminary analysisIntroductionProposalGSI facility & setup

Tracking layers XY (60 segm.) 60x60 mm2 (0.3mm thick)2 SSSD (7 segm.) 60x40 mm2 (1mm thick)3 DSSD (implantation area, 60x40 segm.): 60x40 mm2 (0.7mm thick)2 SSSD (7 segm.) 60x40 mm2 (1mm thick)

Neutron detector for FRS-GSI S410 experiment

30 3He counters: 20 with 20 atm pressure 10 with 10 atm pressure

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GSI facility & setupPreliminary analysisIntroductionProposalGSI facility & setup

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Data analysis method based in Go4 & rootGSI facility & setupPreliminar analysisIntroductionProposal

Identification plotTracking signals FRS detectors

A/QZBiPoPbTlHgPreliminary analysisGSI facility & setup

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Data analysis method based in Go4 & rootGSI facility & setupPreliminary analysisIntroductionProposalPreliminary analysis

A/QZ205BiCalibration files for Z and AoQ (ID): 205Bi & 216Po

keVkeVCountsCountsGamma rays of Isomers881698286796

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Data analysis method based in Go4 & rootGSI facility & setupPreliminar analysisIntroductionProposalPreliminary analysis

Location on silicon layer detector (SIMBA)

ImplantationCountsEnergy deposited (ch)NoiseBeta decay

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Data analysis method based in Go4 & rootGSI facility & setupPreliminar analysisIntroductionProposalPreliminary analysis

- - n n

keVChBeta disintegrationsImplants- decays calibrations will be performed with a 137Cs source- decay curves will provide half lives values

252Cf for BELEN efficiency

PulserNoiseNeutron signalCountsEnergy (ch)The end!

GRETER research group - Nuclear Engineering Section (SEN)Thanks to the fellowship of the Ctedra ARGOS

www-w2k.gsi.de/frs-setup