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14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15- 19, 2015 G. Tagliente – INFN Bari Recent results in Nuclear Astrophysics.

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Presentation on theme: "14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15- 19, 2015 G. Tagliente – INFN Bari Recent results in Nuclear Astrophysics."— Presentation transcript:

1 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15- 19, 2015 G. Tagliente – INFN Bari Recent results in Nuclear Astrophysics @ n_TOF, CERN Tagliente Giuseppe Istituto Nazionale Fisica Nucleare, Sez. di Bari (on behalf of the n_TOF collaboration) 14 th International Conference On Nuclear Reaction Mechanisms

2 ( ~ 100 Researchers from 30 Institutes) CERN Technische Universitat Wien Austria IRMM EC-Joint Research Center, GeelBelgium Charles Univ. (Prague)Czech Republic IN2P3-Orsay, CEA-SaclayFrance KIT – Karlsruhe, Goethe University, FrankfurtGermany Univ. of Athens, Ioannina, DemokritosGreece INFN Bari, Bologna, LNL, LNS, Trieste, ENEA – BolognaItaly Univ. of TokioJapan Univ. of LodzPoland ITN LisbonPortugal IFIN – BucarestRumania CIEMAT, Univ. of Valencia, Santiago de Compostela, University of Cataluna, SevillaSpain University of Basel, PSISwitzerland Univ. of Manchester, Univ. of YorkUK 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari The n_TOF Collaboration

3 –Neutron cross sections relevant for Nuclear Astrophysics –Measurements of neutron cross sections relevant for Nuclear Waste Transmutation and related Nuclear Technologies (ADS) –Neutrons as probes for fundamental Nuclear Physics 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari n_TOF Scientific Motivations

4 H 30 000 C 10 Fe 1 Au 2 10 -7 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari Gap B,Be,Li Fe peak s-process peaks (nuclear shell closures) r-process peaks (nuclear shell closures) AuPb Th, U NEUTRONS Elements heavier than Fe are the result of neutron capture processes  -nuclei 12 C, 16 O, 20 Ne, 24 Mg, …. 40 Ca Abundances beyond Fe–ashes of stellar burning

5 neutrons The canonical s-process s-process lifetime 10 4 years n n ≈10 6 -10 12 neutron/cm 3 r-process lifetime  s n n ≈10 22 neutron/cm 3  -decay lifetime: few hours to few years Nucleosynthesis

6 Stellar Models 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

7 Low mass Asympotic Giant Branch (AGB) M≈ 1.5 - 3 M  13 C( ,n) 16 O T ~ 8 keV N n < 10 7 n/cm 3 22 Ne( ,n) 25 Mg T ~ 23 keV N n ~10 10 -10 12 n/cm 3 22 Ne( ,n) 25 Mg In core He-burning T ~ 26 keV N n ~ 10 6 n/cm 3 In core C-burnig T ~ 90 keV N n ~10 11 n/cm 3 s-process stellar sites Massive stars M≈ 15 - 25 M 

8 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari n_TOF Goal *** cross section uncertainties <5% *** safe control of systematic uncertainties

9 n_TOF Goal

10 n_TOF Time line Concept by C.Rubbia CERN/ET/Int. Note 97-19 1997 2000 Commissioning Construction started 1999 New Target installed 2008 2001-2004 Phase I Measurement campaign 63 Ni 62 Ni Phase II Measurement campaign 2009-2012 Commissioning 2009 2 nd Exp. area 2014 Upgrades 10 B-water Class-A area 2010 Phase III 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

11 151 Sm 204,206,207,208 Pb,209 Bi 24,25,26 Mg 90,91,92,94,96 Zr, 93 Zr 139 La 186,187,188 Os Cross sections relevant in Nuclear Astrophysics s-process: branchings abundancies in presolar grains Magic nuclei Isotopes of particular interess In the period 2002-2004 measured long-needed capture and fission cross-sections for 36 isotopes, 18 of which radioactive. The unprecedented combination of excellent resolution, unique brightness and low background has allowed to collect high-accuracy data, in some cases for the first time ever. 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari The experimental activity at n_TOF: Ph I

12 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari n_TOF Phase II

13 54,56,57 Fe 58,60,62 Ni, 63 Ni 63 Ni 25 Mg 93 Zr Cross sections relevant in Nuclear Astrophysics s-process: seeds isotopes In the period 2009-2012 measured long-needed capture and fission cross-sections for 22 isotopes, 14 of which radioactive. 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari The experimental activity @ n_TOF: Ph II

14 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari n_TOF Phase III

15 Isot.RComments 147 Pm (n,  ) Branching point 26 Al (n,p/  ) 26 Al galactic abundance 7 Be (n,  ) n capture in light nuclei Isot.RComments 70,72,73 Ge (n,  ) s-process flow 171 Tm171 Tm, 204 Tl (n,  ) Branching points 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari AstroPhysics program EAR I & EAR II

16 There is need of accurate new data on neutron cross-sections for astrophysics. Since 2001, n_TOF@CERN has provided an important contribution to the field, with an intense activity on capture measurements. Several results of interest for stellar nucleosynthesis (Sm, Os, Zr, Ni, Fe, etc…). To date, high resolution measurements performed in EAR1 in optimal conditions (borated water moderator, Class-A experimental area, etc…). The EAR2 has opened new perspectives for frontier measurements on short- lived radionuclides. 16 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari Conclusions

17 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

18 Nucleus N ʘ Normalized to N(Si)=10 6 atoms N s / N ʘ % Old N s / N ʘ % n_TOF 90 Zr5.5460.7890.844 91 Zr 1.211.0661.024 92 Zr 1.8481.0520.981 94 Zr 1.8731.2171.152 96 Zr 0.3020.8420.321 The s-abundances, N s, are calculated using the TP stellar model for low mass AGB star (1.5 - 3 M  ). Solar abundances, N , from Lodders 2009, accuracy 10% 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari Courtesy of R. Gallino and S. Bisterzio The experimental results: Zr isotopes

19 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari The experimental results: 186,187 Os

20 Cosmological way Cosmological way Astronomical way Nuclear way: Re/Os clock Th/U clock 13.7  0.2 Gyr 14  2 Gyr 14.9  2 Gyr(*) (*) 0.4 Gyr uncertainty due to cross-sections 14.5  2.5 Gyr The experimental results: 186,187 Os 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

21 s-Process 150 Sm 152 Sm 151 Eu 153 Eu 152 Gd 154 Gd The branching ratio for 151 Sm depends on: Termodynamical condition of the stellar site (temperature, neutron density, etc…) Cross-section of 151 Sm(n,  ) 151 Sm used as stellar thermometer !! 151 Sm 152 Eu 154 Eu 153 Sm The experimental results: 151 Sm Laboratory t 1/2 = 93 yr reduced to t 1/2 = 3 yr @ s-process site 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

22 Measured for the first time at a time-of-flight facility Resonance analysis with SAMMY code. Maxwellian averaged (n,γ) cross section of the 151 Sm and previous calculation (symbol) NO PREVIOUS MEASUREMENTS! Maxwellian averaged cross-section experimentally determined for the first time s-process in AGB stars produces 77% of 152 Gd, 23% from p process The experimental results: 151 Sm background

23 Scenarios in massive stars The experimental results: 63 Ni 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

24 63 Ni (t 1/2 =100 y) represents the first branching point in the s-process, and determines the abundance of 63,65 Cu First high-resolution measurement of 63 Ni(n,  ) in the astrophysical energy range. 62 Ni sample (1g) irradiated in thermal reactor (1984 and 1992), leading to enrichment in 63 Ni of ~13 % (131 mg) In 2011 ~15.4 mg 63 Cu in the sample (from 63 Ni decay). After chemical separation at PSI, 63 Cu contamination <0.01 mg The experimental results: 63 Ni 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

25 Isotope production @ILL 171 Tm: 170 Er(n, γ) 171 Er (β -, 7.5h) 171 Tm (enrichment 1.8%) 3.6 mg of 171 Tm (1.9 y) [1.3x10 19 atoms] Chemical separation and sample preparation @PSI 171 Tm (97.9%) + 169 Tm (2.1%) + 170 Tm(0.07%) 171 Tm deposit (20 mm diameter) Frame (50 mm diameter) Mylar (5  m) Aluminum (7  m) backing 1975198019851990199520002005 200 400 600 800 1000 1200 1400 637 1332 399 309 243 KADoNiS = 486 MACS @30 keV (mb) YEAR The experimental results: 171 Tm(n, γ) 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

26 VERY PRELIMINARY RESULTS First experimental measurement The experimental results: 171 Tm(n, γ) 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

27 The neutron capture cross section on Ge affects the abundances for a number of heavier isotopes up to a mass number of A = 90. The experimental results: Ge(n, γ) 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

28 The experimental results: 73 Ge(n, γ) ENDF/B-VII n_TOF ENDF/B-VII n_TOF VERY PRELIMINARY RESULTS

29 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari The experimental results: 70 Ge(n, γ) Counts ENDF/B-VII n_TOF VERY PRELIMINARY RESULTS

30 Observation of the cosmic ray emitter 26 Al is proof that nucleosynthesis is ongoing in our galaxy. The neutron destruction reactions 26 Al(n, p) and 26 Al(n, α) are the main uncertainties to predict the galactic 26 Al abundance. There are only few experimental data on these reactions and they exhibit severe discrepancies. 26 Al(n, p), (n, α) 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

31 26 Al(n, p), (n, α) The p and  will be detected by double sided silicon strip detectors arranged as E –  E telescope The sample was produced by IRMM in collaboration with LANCSE The neutron fluence will be monitored by a 10 B sample

32 BBN successfully predicts the abundances of primordial elements such as 4 He, D and 3 He * A serious discrepancy (factor 2-4) between the predicted abundance of 7 Li and the value inferred by measurements Cosmological Lithium Problem 7 Be(n, p), (n, α) 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

33 Approximately 95% of primordial 7 Li is produced from the electron capture decay of 7 Be (T 1/2 =53.2 d) 7 Be is destroyed via (n,p) (≈97%) and (n, α) (≈2.5%) reactions A higher destruction rate of 7 Be can solve or at least partially explain the Cosmological Lithium Problem 7 Be(n, p) 7 Be(n, α) Only one direct measurement (P. Bassi et al., 1963, @ 0.025 eV) 7 Be(n, p), (n, α) 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

34 neutrons Silicon 1 Silicon 2 sample Sandwich of silicon detectors directly inserted in the beam Detection of both alpha particles (E≈9 MeV) Coincidence technique: Strong rejection of background Sample: 1-10  g of 7 Be from water cooling of SINQ spallation target. (activity of 478 keV  -rays 1 GBq/  g) Isotopic composition: 1:1 7 Be- 10 Be 1:5 7 Be- 9 Be 7 Be(n, p), (n, α) 14th International Conference on Nuclear Reaction Mechanisms – Varenna, June 15-19, 2015 G. Tagliente – INFN Bari

35 proton diffusion 13 C  n) 16 O 22 Ne  n) 25 Mg - C 10 -4 neutron density time neutron density time

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