Decay properties of neutron-rich nuclei on the r-process path

Transcription

1 Nuclear science frontier explored by ultra-high power lasers, Feb. 03 Osaka Decay properties of neutron-rich nuclei on the r-process path Shunji NISHIMURA ( RIKEN Nishina Center / NAOJ)

2 Nuclear Parameters from Decay Spectroscopy First E(2+) for even-even nuclei kev - Decay curve : T 1/2 - Excited states : E(2 + ),.. - Isomeric states - New magic number? - Disappearance? - Shell quenching? - Deformation? - Q β - Neutron emission (P n ) D.Steppenbeck et al. In-beam gamma (RIBF) Isomer and beta decay near 78 Ni, 128 Pd 54 Ca

3 R-Process Nucleosynthesis C.Freiburghause et al. ApJ 516 (1999) Issue around mass A = Half-lives (T 1/2 ) abundance process speed Masses (A, Q β, S n ) Neutron capture (n,γ) location of the path β-delayed neutron (P n ) final abundances ν (ν) catupures Half-lives (T 1/2 ) strongly depends on nuclear structure. - determined by Q β -value from the mass difference of nuclide and its daughter. - Sensitive to deformation.

4 Location of Decay Station Decay Exp. 238 U 345 MeV/u, Intensity = 5 12 pna!

5 Decay Programs at RIBF β-γ 110 Zr region (3-days) β-n [ high efficiency ] 3 He counters (x 27) β-γ-n [fast timing] CAITEN Project *PLB 696, 186 (2011) *PRL. 106, (2011) 2011 *PRL. 106, (2011) *PLB 704, 270 (2011) 2012 EURICA Project WAS3ABi (Si) Neutron detectors BRIKEN Project - LaBr3 detectors - Neutron detector (NiGIRI) *PRC 88, (2013) *PRL 111, (2013) *PRL submitted. BELEN (Spain) +3Hen (ORNL) +Russia+RIKEN

6 Beam production and Decay Station Silicon strip detector STOP Detector ( Decay experiment ) Beam MeV/u Be target - Charge F5 - F11

7 Experimental Setup in 2009 γ-ray RI & β-ray detection 9 DSSDs (50 x 50 x 1 mm 3 ) 16 x 16 strips ~ 2000 pixels in total β-ray The implantation of an identified RI is associated with the following β-decay events that are detected in the same DSSSD pixel ΔE-TOF-Bρ method using the focal plane detectors in BigRIPS

8 EURICA Project at RIBF Euroball Cluster detectors Support structure Readout electronics used for GSI-RISING RIKEN RIBF (Japan) Installation completed in 2012 Feb.

9 Beta-counting system: WAS3ABi (Wide-range Active Silicon-Strip Stopper Array for Beta and ion detection) (a) (b) (c) SIMBA WAS3ABi (d) Nitrogen air cooling ~ 10 degree. (a) 14,000pixels + Plastic (Qbeta) (b) 12,000pixels + Plastic (Fast timing) (c) 7,200 pixels + 10 x SSD (Qbeta) SIMBA Installed in WAS3ABi (d) 16,000 pixels + Plastic (Veto) 2012 U-beam 2013 U-beam 2013 Xe-beam 2013 Xe-beam

10 RIBF Decay Spectroscopy I.U.Roederer, ApJ 747, L8 (2012) ORNL, MSU, ISOLDE, Half-lives measured (T 1/2 >1ms with color) [ 2009] Zr region (RIBF) [2012] 78 Ni (Z=28,N=50) Beta-decay half-lives 132 Sn (Z=50, N=82) region Pd (N=82) Sn (Z=50) [2013] Mid-shell neutron-rich nuclei Mass A=~70, ~110, ~140, ~150, ~160 [Future]

11 Decay Experiment in 2009 Zr and Nb decay faster than expected by FRDM+QRPA ( T 1/2 : 1/2 ~ 1/3 )

12 Decay Spectroscopy in the vicinity of double magic 78 Ni (Z=28, N=50) Z.M.Niu, PLB 723 (2013) [ History of 78 Ni ] Identified as sew isotope (3 events) M.Bernas et al., PLB415 (1997) Beta-decay half-life (11 events) T 1/2 ~ ms T.Hosmer et al., PRL94 (2005)

13 RIBF: Decay Experiment around 78 Ni region Spokesperson : SN Atomic number Produced RI at RIBF R-process path 78 Ni A/Q Implantation rate = 20 ~ 50 pps

14 Decay properties around double magic 132 Sn ( Z=50, N=82 ) masses New isomers around 132Sn region T 1/2 * 133Cd * * * Half-lives of Cd isotopes J. Hakala et al., Phys. Rev. Lett. 109 (2012)

15 Most Neutron-Rich N=82 Isomer with EURICA (r-process waiting point) T 1/2 of Cd isotopes A.Jungclaus, PRL99, (2007) No evidence for shell quenching N=80 N=82 H. Watanabe, G. Lorusso et al., accepted in PRL No evidence for shell-quenching in 128 Pd.

16 First Excited State: E(2+) T.Sumikama et al. PRL 106, (2011) G.Simpson et al. Submitted to PRL H.Watanabe et al. Accepted in PRL P.-A.Soederstroem et al. PRC 88, (2013)

17 Beta-decay flow with neutron emission FRDM + QRPA Beta-delayed gamma-rays will be powerful method for multi neutron emissions

18 Produced exotic nuclei so far in EURICA campaign 170 Dy: Watanabe, Soederstrom, Regan, Walker 59 Ge: Blank 64,66 Se: Rubio,Fujita,Gelletly 71 Kr: Algora, de Angelis, Rechia, Rubio 53,54 Ca: Valiente-Dobon, Steppenbeck

19 In five years (U-beam int. > 100 pna!?) Several hundreds of new beta-decay half-lives in five years. Significant contribution in nuclear structure and r-process nucleosynthesis.

20 Summary The EURICA project started surveying decay properties of exotic nuclei on the r-process path. Beta-decay half-lives Excited states Beta-delayed neutron Isomeric states Possible Q beta measurement Advanced detection system Beta-gamma spectroscopy (EURICA) Beta-gamma-neutron spectroscopy (BRIKEN, CAITEN+NiGIRI) A lots of results are coming from RIKEN RIBF!

21 Thank you.

22 EURICA Collaboration and Support 2012 Nov.-Dec May 2012 June Collaboration: Tohoku, Univ. Tokyo, Brighton Univ. Debrecen, Joseph Fourier, Osaka Univ. Peking, LPSC, IBS, Oslo, Consejo Sup. De Inv. Cientificas, IPN Orsay, Padova, Leuven, SKKU, INFN, ANU, Koeln, TU Muenchen, Fisica, Legnaro, ATOMKI, INFN-Milano, INFN-Firenze, INFN-LNL, Univ. di Padova, Surrey, GSI, ANL, Yale, Milano, Univ. Madrid, Tech. Univ. Darmstadt, Univ. Istanbul, CNS, CEA, RCNP, Univ. Notre Dame, Inst. voor Kern-en Stralings Fysica, Hoseo Univ., Univ. Tsukuba, Inst. Plurid. Hubert Curien, and RIKEN

23 Direct (n,γ) reaction measurement Crazy idea: Is it impossible..? Radioactive isotopes (RI) + (reference nuclei) Example.. 130Cd (n,γ)131cd RI storage instrument MR-TOF / Penning Trap Mass measurement THM? (Kubono san s talk) Neutron beam - High intensity - Small focus point - Pulsed beam Check mass A +1