Tagliente Giuseppe Is#tuto Nazionale Fisica Nucleare, Sez. di Bari (on behalf of the n_tof collabora#on)

Transcription

1 Recent results in Nuclear n_tof, CERN Tagliente Giuseppe Is#tuto Nazionale Fisica Nucleare, Sez. di Bari (on behalf of the n_tof collabora#on)

2 The n_tof Collabora<on 1 Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

3 The n_tof Collabora<on CERN Technische Universitat Wien (~100 Researchers from 30 Ins2tutes) Austria IRMM EC-Joint Research Center, Geel Belgium Charles Univ. (Prague) Czech Republic IN2P3-Orsay, CEA-Saclay France KIT Karlsruhe, Goethe University, Frankfurt Germany Univ. of Athens, Ioannina, Demokritos Greece INFN Bari, Bologna, LNL, LNS, Trieste, ENEA Bologna Italy Univ. of Tokio Japan Univ. of Lodz Poland ITN Lisbon Portugal IFIN Bucarest Rumania CIEMAT, Univ. of Valencia, SanUago de Compostela, University of Cataluna, Sevilla Spain University of Basel, PSI Univ. of Manchester, Univ. of York UK Switzerland Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

4 n_tof Scien<fic Mo<va<ons 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 Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

5 n_tof Goal *** cross section uncertainties <5% *** safe control of systematic uncertainties Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

6 n_tof Goal Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

7 Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari The CERN n_tof Facility n_tof 200m Tunnel Sample Pb Spallation Target Proton Beam 20GeV/c 7x10 12 ppp Booster 1.4 GeV Neutron Beam 10 o prod. angle Linac 50 MeV PS 20GeV

8 The n_tof Facility: Beam lines Both beam lines have: 1st collimator for halo cleaning and first beam shaping Filter sta<on Magnet to minimize the charged par<cle background 2nd collimator for beam shaping EAR-2: Ver<cal flight path of 18.2 m EAR-1: Horizontal flight path of m Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

9 The n_tof Facility: Main features EAR-1 EAR-2 Wide energy range 25 mev<e n <1 GeV 25 mev<e n <300 MeV Extremely high instantaneous neutron flux 10 5 n/cm 2 /pulse 10 6 n/cm 2 /pulse Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

10 The n_tof Facility: Main features EAR-1 EAR-2 Wide energy range 25 mev<e n <1 GeV 25 mev<e n <300 MeV Extremely high instantaneous neutron flux 10 5 n/cm 2 /pulse 10 6 n/cm 2 /pulse Low repe<<on rate <0.8 Hz (1 pulse/2.4 s maximum) High resolu<on in energy ΔE/E=10-4 (E n < 10 kev) ΔE/E=10-3 (E n < 10 kev) Unique facility for measurements of radioacuve isotopes and low cross-secuons: Branch point isotopes (astrophysics) Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

11 n_tof Time line TARC experiment May 1998 Feasibility CERN/LHC/ Add 2000 Commissioning Problem Inves<ga<on May 2009 Commissioning 2010 July 2014 Upgrades: Borated-H 2 O Class-A Second Line Commissioning 2015 Phase Aug Proposal submihed Concept by C.Rubbia CERN/ET/Int. Note ConstrucUon started Response (counts / ns) Neutron Energy / ev Phase I Isotopes Capture: 25 Fission: 11 n-tof 232 Th ( at/b) 208 Pb GELINA 232 Th ( at/b) 208 Pb 2008 New Target construc<on Phase II Isotopes Capture: 14 Fission: 3 (n,cp): EAR2 Design and Construc<on Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

12 The experimental acuvity at n_tof: Ph I n Cross sec<ons relevant in Nuclear Astrophysics n s-process: branchings n abundancies in presolar grains n Magic nuclei n Isotopes of par<cular interess 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 In the period 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. Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

13 The experimental n_tof: Ph II n Cross sec<ons relevant in Nuclear Astrophysics n s-process: seeds isotopes 54,56,57 Fe 58,60,62 Ni, 63 Ni 25 Mg 93 Zr In the period measured long-needed capture and fission cross-sections for 22 isotopes, 14 of which radioactive. Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

14 AstroPhysics EAR I & EAR II: Phase III Isot. R Comments 70,72,73 Ge (n,γ) s-process flow 171 Tm, 204 Tl (n,γ) Branching points 88 Sr, 89 Y (n,γ) Neutron Magic, 1 st s- process peek Isot. R Comments 147 Pm (n,γ) Branching point 26 Al (n,p/α) 26 Al galac<c abundance 7 Be (n,p/α) n capture in light nuclei Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

15 Conclusions There is need of accurate new data on neutron cross-sec<on for astrophysics. Since 2001, has provided an important contribu<on to the field, with an intense ac<vity on capture and fission measurements. Several results of interest for stellar nucleosynthesis (Sm, Ni, Os, Zr, Fe, Mg etc ). High resolu<on measurements performed in EAR1 in op<mal condi<ons (borated water moderator, Class-A experimental area, etc ). The EAR2 has opened new perspecuves for fron<er measurements on shortlived radionuclides. Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

16 Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

17 The experimental results: Zr isotopes Courtesy of R. Gallino and S. Bisterzio Nucleus N ʘ N s / N ʘ % N s / N ʘ % Normalized to Old n_tof N(Si)=10 6 atoms 90 Zr Zr Zr Zr Zr Solar abundances, N, from Lodders 2009, accuracy 10% The s-abundances, N s, are calculated using the TP stellar model for low mass AGB star (1.5-3 M ). Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

18 The experimental results: 186,187 Os 187 Os c = 187 σ (186) σ (187) Os = σ (186) σ (187) 0.42 ± 186 Os 0.02 Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

19 The experimental results: 186,187 Os Cosmological way Astronomical way 13.7 ± 0.2 Gyr 14 ± 2 Gyr Nuclear way: Re/Os clock 14.9 ± 2 Gyr(*) Th/U clock 14.5 ± 2.5 Gyr (*) 0.4 Gyr uncertainty due to cross-sec<ons Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

20 The experimental results: 151 Sm Laboratory t 1/2 = 93 yr reduced to t 1/2 = 3 s-process site 152 Gd 154 Gd 151 Eu 152 Eu 153 Eu 154 Eu s-process 150 Sm 152 Sm 151 Sm 153 Sm The branching ra<o for 151 Sm depends on: Termodynamical condiuon of the stellar site (temperature, neutron density, etc ) Cross-sec<on of 151 Sm(n,γ) 151 Sm used as stellar thermometer!! Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

21 The experimental results: 151 Sm background Measured for the first time at a time-of-flight facility Resonance analysis with SAMMY code. Maxwellian averaged cross-section experimentally determined for the first time s-process in AGB stars produces 77% of 152 Gd, 23% from p process Maxwellian averaged (n,γ) cross section of the 151 Sm and previous calculation (symbol) NO PREVIOUS MEASUREMENTS! Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

22 The experimental results: 63 Ni Scenarios in massive stars Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

23 The experimental results: 63 Ni Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari 63 Ni (t 1/2 =100 y) represents the first branching point in the s-process, and determines the abundance of 63,65 Cu 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). Aser chemical separa<on at PSI, 63 Cu contamina<on <0.01 mg First high-resoluuon measurement of 63 Ni(n,γ) in the astrophysical energy range.

24 The experimental results: 171 Tm(n, γ) kev (mb) Isotope 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] KADoNiS = Chemical separauon and sample 171 Tm (97.9%) Tm (2.1%) Tm(0.07%) YEAR Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari 171 Tm deposit (20 mm diameter) Aluminum (7 µm) backing Frame (50 mm diameter) Mylar (5 µm)

25 The experimental results: 171 Tm(n, γ) data: J. Lerendegui VERY PRELIMINARY RESULTS Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari First experimental measurement

26 The experimental results: Ge(n, γ) The neutron capture cross sec<on on Ge affects the abundances for a number of heavier isotopes up to a mass number of A = 90. Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

27 The experimental results: 73 Ge(n, γ) ENDF/B-VII n_tof VERY PRELIMINARY RESULTS data: C. Lederer Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari ENDF/B-VII n_tof

28 The experimental results: 70 Ge(n, γ) Counts ENDF/B-VII n_tof VERY PRELIMINARY RESULTS data: C. Lederer Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

29 26 Al(n, p), (n, α) Observa2on of the cosmic ray emi;er 26 Al is proof that nucleosynthesis is ongoing in our galaxy. The neutron destruc2on reac2ons 26 Al(n, p) and 26 Al(n, α) are the main uncertain2es to predict the galac2c 26 Al abundance. There are only few experimental data on these reac2ons and they exhibit severe discrepancies. Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

30 26 Al(n, p), (n, α) The sample was produced by IRMM in collabora<on with LANCSE The p and α will be detected by double sided silicon strip detectors arranged as E ΔE telescope The neutron fluence will be monitored by a 10 B sample Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

31 7 Be(n, p), (n, α) 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 Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

32 7 Be(n, p), (n, α) Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari 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%) reac<ons A higher destruc<on rate of 7 Be can solve or at least par<ally explain the Cosmological Lithium Problem Only one direct measurement (P. Bassi et al., ev) 7 Be(n, p) 7 Be(n, α)

33 7 Be(n, α) Intrinsic difficulty of the measurement Sandwich of silicon detectors directly inserted in the beam low cross secuon Detec<on of both alpha par<cles (E 9 MeV) extremely high specific acuvity: 13 GBq/µg Coincidence technique: Silicon 1 sample Strong rejection available of in small quanuty background neutrons Silicon 2 short half-life: 53.3 days Sample: 1.4 µg of 7 Be from water cooling of SINQ spallation target. (activity of 478 kev γ-rays) Isotopic composition: 1:1 7 Be- 10 Be 1:5 7 Be- 9 Be Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

34 7 Be(n,α) cross-secuon Accepted by PRL Courtesy of M. Barbagallo 1/v behaviour of the 7 Be(n,α) 4 He reacuon cross-secuon. The only previous measurement (@0.025 ev) is in good agreement with new data Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

35 7 Be(n, p) Telescope of silicon detectors (E DE) Detected proton (E 1.6 MeV) p E E High purity sample needed: PSI+ ISOLDE 1.1 GBq acuvity of the sample Neutron beam Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

36 neutron density <me neutron density 10-4 <me - C proton diffusion 13 C(α,n) 16 O 22 Ne(α,n) 25 Mg Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari

37 The experimental results: 25 Mg(n, γ) The 25 Mg is one of the most important neutron poison in the s-process path. The 22 Ne(α,n) is one of the main source of neutrons for the s-process. Extremely difficult to measure (very low cross sec<on). ReacUon rate very uncertain because of the poorly known property of the states in 26 Mg. Resonance Analysis: simultaneous analysis of transmission (GELINA) and capture data (n_tof) Spin assignment and constraints for 22 Ne(α,n) 25 Mg Library E R =72 kev, J π =2 + E R =79 kev, J π =3 + This work E R =72 kev, J π =2 + E R =79 kev, J π =3 - Interna<onal Nuclear Physics Conference Adelaide, September 11-16, 2016 G. Tagliente INFN Bari