Presentation is loading. Please wait.

Presentation is loading. Please wait.

Neutron induced reactions: Experiments and Theory 1.BANG! Stuff with light nuclei (BBN, Coul_diss exp, C x-sections) 2.The Metals & the s-process (canonical.

Published byHugo Martin Modified over 8 years ago

Similar presentations

Presentation on theme: "Neutron induced reactions: Experiments and Theory 1.BANG! Stuff with light nuclei (BBN, Coul_diss exp, C x-sections) 2.The Metals & the s-process (canonical."— Presentation transcript:

1 Neutron induced reactions: Experiments and Theory 1.BANG! Stuff with light nuclei (BBN, Coul_diss exp, C x-sections) 2.The Metals & the s-process (canonical s-process, Fe-60) 3.Heavy (Sm, Nd, etc.) 4.Specials: The Re/Os clock a.mengoni@iaea.org

2 Ages Cosmological way Cosmological way based on the Hubble time definition (“expansion age”) Astronomical way Astronomical way based on observations of globular clusters Nuclear way Nuclear way based on abundances & decay properties of long-lived radioactive species

3 The most recent estimate of the Hubble constant based on observations provides( *) : H 0 = 72  8 km/sec/Mpc and implies an age of: Age from Hubble time 13.9  1.5 Gyr (*) HST Key Project see: WL Friedman et al., ApJ 553, (2001) 47 NB: if  =  m ~1, then age=2/3×1/H 0 = 9.3  1.0 Gyr

4 The detailed structure of the cosmic microwave background fluctuations will depend on the current density of the universe, the composition of the universe and its expansion rate. WMAP has been able to determine these parameters with an accuracy of better than 5%. Thus, we can estimate the expansion age of the universe to better than 5%. When we combine the WMAP data with complimentary observations from other CMB experiments (ACBAR and CBI), we are able to determine an age for the universe closer to an accuracy of 1%. Age from WMAP observations Source: CL Bennett et al., ApJS, 148 (2003) 1 13.7  0.2 Gyr

5 Cosmological “problems” with age http://map.gsfc.nasa.gov/

6 Cosmological “problems” with age

7 Age from globular clusters The age derived from observation of the luminosity-color relation of stars in globular clusters

8 Age from globular clusters alberto.mengoni@cern.ch from > 11.2 Gyr (*) to 14  2.0 Gyr (*) LM Krauss and B Chaboyer, Science 299 (2003) 65 The age derived from observation of the luminosity-color relation of stars in globular clusters Source: DN Spergel et al. Proc. Natl. Acad. Sci. USA 94 (1997) 6579

9 The nuclear way Traditional nuclear clocks are those based on: 235 U/ 238 U 232 Th/ 238 U 187 Os/ 187 Re Th/Eu, Th/X or Th/U abundances in low-Z stars

10 Tuning the Re/Os clock: neutron cross sections Re/Os Measurements at CERN n_TOF & at FZK Stellar rates Uncertainties

11 Time Now4.5 Gyr ? Solar-system formation Galaxy formation BANG!

12 Re/Os clock W W 182 26.3 Re Os Re 183 71 d Os 184 0.02 W 183 14.3 W 184 30.67 W 185 75.1 d W 186 28.6 W 187 23.8 h W 188 69 d Re 184 38 d Re 185 37.4 Re 186 90.64 h Re 187 62.6 42.3x10 9 a Re 188 16.98 h Re 189 24.3 h Re 190 3.1 m Os 185 94 d Os 186 1.58 Os 187 1.6 Os 188 13.3 Os 189 16.1 Os 190 26.4 Os 191 15.4 d Os 192 41.0 Now4.5 Gyr BANG! The  -decay half-life of 187 Re is 42.3 Gy ? Effect on the abundance of the decay daugther 187 Os

13 Re/Os clock(*) W W 182 26.3 Re Os Re 183 71 d Os 184 0.02 W 183 14.3 W 184 30.67 W 185 75.1 d W 186 28.6 W 187 23.8 h W 188 69 d Re 184 38 d Re 185 37.4 Re 186 90.64 h Re 187 62.6 42.3x10 9 a Re 188 16.98 h Re 189 24.3 h Re 190 3.1 m Os 185 94 d Os 186 1.58 Os 187 1.6 Os 188 13.3 Os 189 16.1 Os 190 26.4 Os 191 15.4 d Os 192 41.0 s-only r-processr-only s-process Now4.5 Ga BANG! ? (*) DD Clayton, ApJ 139 (1964) 637 >>>>

14 Key quantity: cross sections Now4.5 Ga BANG! t0t0 s-process condition:  (186)N(186) ≈  (187)N(187)

15 Enhanchement of [ 187 Os] by 187 Re(  - ) alberto.mengoni@cern.ch The s-process condition  A N A = const. implies that:  186 [ 186 Os] =  187 [ 187 Os] From (n,  ) systematics 0.5  186 /  187 ~ 0.5 On the other hand, from solar-system abundances: 0.7924 ± 0.0016 [ 187 Os] / [ 186 Os] = 0.7924 ± 0.0016

16 The n_TOF facility at CERN www.cern.ch/n_TOFThe n_TOF Collaboration

17 Pulse height weighting technique Correction of the  -response by weighting function to make the detector efficiency proportional to  -ray energy Neutron flux monitor Silicon detectors viewing a thin 6 LiF foil -ray detection: C 6 D 6 scintillators C6D6C6D6 C6D6C6D6 Neutron beam Sample changer Os measurements setup The n_TOF Collaborationwww.cern.ch/n_TOF

18 186 Os 186 Os (2 g, 79 %) 187 Os 187 Os (2 g, 70 %) 188 Os 188 Os (2 g, 95 %) Al can Al can environmental background 197 Au 197 Au (1.2g) flux normalization (using Ratynski and Macklin high accuracy cross section data) nat Pb nat Pb (2 g) in-beam gamma background nat C nat C (0.5 g) neutron scattering background Samples & capture yields M Mosconi, FZK www.cern.ch/n_TOF

19 The n_TOF Collaboration n_TOF-04: 186 Os capture x-section MACS-30 BrB81438 ± 30 mb WiM82418 ± 16 mb n_TOF 414 ± 17 mb NB: the calculation is normalized NOT fitted to experimental data

20 Hauser-Feschbach theory: (statistical model) Neutron transmission coefficients, T n : from OMP calculations  -ray transmission coefficients, T   : from GDR (experimental parameters) Nuclear level densities: fixed at the neutron binding from exp n_TOF-04: 186 Os capture x-section www.cern.ch/n_TOF

21 The n_TOF Collaborationwww.cern.ch/n_TOF n_TOF-04: 187 Os capture x-section MACS-30 BrB81919 ± 43 mb WiM82874 ± 28 mb n_TOF 969 ± 32 mb NB: the calculation is normalized NOT fitted to experimental data

22 Key quantity: cross sections Now4.5 Ga BANG! t0t0

23 The clock: from x-sections to age Now4.5 Gyr BANG! t0t0 e -  t r-process enrichment of 187 Re s-process synthesis of 186,187 Os

24 Laboratory cross sections & the clock Now4.5 Ga BANG! t0t0 R  = 0.43 ± 0.02 t 0 = 8.7 ± 0.4 Ga age: 8.7 + 4.6 = 13.3 Ga

25 Stellar 187 Os(n  ) rate 187 Os at kT = 30 keV: P(gs) = 33% P(1st) = 47% P(all others) = 20% a.mengoni@iaea.org SE Woosley and WA Fowler, ApJ 233 (1979) 411 A.Include thermal population B.Include super-elastic scattering channels C.Nuclear structure effects (deformation)  n   * = SEF ∙ <  n,  

26 (n,n’) alberto.mengoni@cern.ch A neutron (inelastic) scattering experiment performed at FZK-Karlsruhe

27 (n,n’) + theory

28

29 www.cern.ch/n_TOF MACS-30 BrB81438 ± 30 mb WiM82418 ± 16 mb n_TOF 414 ± 17 mb a.mengoni@iaea.org CC calculations including ground-state collective band in a deformed OMP n_TOF-04: 186 Os capture x-section

30 www.cern.ch/n_TOF n_TOF-04: 187 Os capture x-section MACS-30 BrB81919 ± 43 mb WiM82874 ± 28 mb n_TOF 969 ± 32 mb a.mengoni@iaea.org CC calculations including ground-state collective band in a deformed OMP

31 Stellar enhancement factor  n   * = SEF ∙ <  n,  

32 Laboratory cross sections & the clock Now4.5 Ga BANG! t0t0 R  = 0.43 ± 0.02 t 0 = 8.7 ± 0.4 Ga age: 8.7 + 4.6 = 13.3 Ga

33 Stellar cross sections & the clock Now4.5 Ga BANG! t0t0 R*  = 0.34 ± 0.02 t 0 = 10.7 ± 0.5 Ga age: 10.7 + 4.6 = 15.3 Ga

34 Uncertainties

35 Abundances: 0.49 Ga x-section ratio*: 0.47 Ga Re-187 b-decay half-life: 0.29 Ga Total uncertainty : < 1 Ga Nuclear Data & Abundances

36 Summary Cosmological way (WMAP observation) Cosmological way (WMAP observation) Astronomical way (globular clusters) Nuclear way: Re/Os clock U/Th clock 13.7  0.2 Ga 14  1 Ga 15.3  0.8 ± 2 Ga(*) (*) 2 Ga uncertainty assigned to GCE modeling + astration(?) >13.4  0.9 ± 2.2 Ga A Frebel et al. ApJ 660 (2007) L117 CL Bennett et al., ApJS, 148 (2003) 1 G Imbriani et al., A&A 420 (2004) 625

37 Now4.5 Ga BANG! U/Th and Re/Os clocks: complementary GCE: independent Primordial yields: model-dependent GCE: dependent Yields: well determined

38 Let’s assume the age from WMAP is correct 13.7  0.2 Gyr

39 Reverse argument Now4.5 Gyr BANG! t0t0 assuming Age = 13.7 Gyr or t 0 = 9.2 Gyr

40 Cosmo-Chronology from others sources Day 1: 8 Gyr Day 2: 4 Gyr Day 3: 2 Gyr Day 4: 1 Gyr Day 5: 1/2 Gyr Day 6: 1/4 Gyr 15.8 Total: 15 ¾ = 15.8 Gyr http://www.geraldschroeder.com/age.html

41 The End

42 Slides annex

43 Brancing(s) W W 182 26.3 Re Os Re 183 71 d Os 184 0.02 W 183 14.3 W 184 30.67 W 185 75.1 d W 186 28.6 W 187 23.8 h W 188 69 d Re 184 38 d Re 185 37.4 Re 186 90.64 h Re 187 62.6 42.3x10 9 a Re 188 16.98 h Re 189 24.3 h Re 190 3.1 m Os 185 94 d Os 186 1.58 Os 187 1.6 Os 188 13.3 Os 189 16.1 Os 190 26.4 Os 191 15.4 d Os 192 41.0 Now4.5 Gyr BANG! The 185 W(n,  ) 186 W rate is needed The inverse 186 W(  n) 185 W cross section has been measured K. Sonnabend et al. ApJ 583 (2003), 506-513. Impact on the age: negligible

44 Re/Os clock W W 182 26.3 Re Os Re 183 71 d Os 184 0.02 W 183 14.3 W 184 30.67 W 185 75.1 d W 186 28.6 W 187 23.8 h W 188 69 d Re 184 38 d Re 185 37.4 Re 186 90.64 h Re 187 62.6 42.3x10 9 a Re 188 16.98 h Re 189 24.3 h Re 190 3.1 m Os 185 94 d Os 186 1.58 Os 187 1.6 Os 188 13.3 Os 189 16.1 Os 190 26.4 Os 191 15.4 d Os 192 41.0 s-only r-processr-only s-process Now4.5 Gyr BANG! ?

45 Nuclear & Astro issues alberto.mengoni@cern.ch The chemical evolution of the galaxy influences the history of the nucleosynthesis Re and Os abundances own uncertainties In addition to the particular conditions which allows to use the Re/Os abundance pair as a clock there are a number of complications: The  -decay half-life of 187 Re is strongly dependent on temperature The stellar neutron capture cross section of 187 Os is influenced by the population of low-lying excited levels (the 1st excited states is at 9.8 keV) Branching(s) at 185 W and/or at 186 Re

46 Issue 1: 187 Re(  - ) decay alberto.mengoni@cern.ch 43.2  1.3 Gyr The  -decay half-life of 187 Re is   = 43.2  1.3 Gyr. Under stellar conditions, the 187 Os and 187 Re atoms can be partly or fully ionized. The  -decay rate can then proceed through a transition to bound-electronic states in 187 Os. The rate for this process can be orders of magnitude faster than the neutral-atom decay. The bound-state  -decay half-life of fully-ionized 187 Re has been measured @ GSI. 32.9  2.0 yr The half-life of fully-ionized 187 Re turns out to be:   = 32.9  2.0 yr. (F. Bosch, et al., PRL 77 (1996) 5190) ≈1 Gyr Impact on the age: ≈ 1 Gyr

47 Stellar 187 Os(n  ) rate For example, in 187 Os at kT = 30 keV it is: P(gs) = 33% P(1st) = 47% P(all others) = 20%

48 The 186 Os(n,  ) cross section: theory Hauser-Feschbach theory: (statistical model) Neutron transmission coefficients, T n : from OMP calculations  -ray transmission coefficients, T   : from GDR (experimental parameters) Nuclear level densities: fixed at the neutron binding from exp All these parameters can be derived and fixed from the analysis of the experimental data at low-energy in the resolved resonance region

49 More on stellar rates

Download ppt "Neutron induced reactions: Experiments and Theory 1.BANG! Stuff with light nuclei (BBN, Coul_diss exp, C x-sections) 2.The Metals & the s-process (canonical."

Similar presentations

Experimental Determination of Neutron Cross Sections of Yttrium by Activation Method by Barbara Geier Supervisors: Assoc. Prof Dr. Wolfgang Sprengel RNDr.

Experimental Determination of Neutron Cross Sections of Yttrium by Activation Method by Barbara Geier Supervisors: Assoc. Prof Dr. Wolfgang Sprengel RNDr.
Branchings, neutron sources and poisons: evidence for stellar nucleosynthesis Maria Lugaro Astronomical Institute University of Utrecht (NL)

Branchings, neutron sources and poisons: evidence for stellar nucleosynthesis Maria Lugaro Astronomical Institute University of Utrecht (NL)
I. Dillmann Institut für Kernphysik, Forschungszentrum Karlsruhe KADoNiS The Sequel to the “Bao et al.” neutron capture compilations.

I. Dillmann Institut für Kernphysik, Forschungszentrum Karlsruhe KADoNiS The Sequel to the “Bao et al.” neutron capture compilations.
Time dependence of SM parameters. Outline Dirac´s hypothesis SM parameters Experimental access to time dependence  laboratory measurements  Quasar absorption.

Time dependence of SM parameters. Outline Dirac´s hypothesis SM parameters Experimental access to time dependence  laboratory measurements  Quasar absorption.
Constraining Astronomical Populations with Truncated Data Sets Brandon C. Kelly (CfA, Hubble Fellow, 6/11/2015Brandon C. Kelly,

Constraining Astronomical Populations with Truncated Data Sets Brandon C. Kelly (CfA, Hubble Fellow, 6/11/2015Brandon C. Kelly,
Introduction to stellar reaction rates Nuclear reactions generate energy create new isotopes and elements Notation for stellar rates: p 12 C 13 N  12.

Introduction to stellar reaction rates Nuclear reactions generate energy create new isotopes and elements Notation for stellar rates: p 12 C 13 N  12.
Introduction to stellar reaction rates

Introduction to stellar reaction rates
Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Neutron capture cross sections on light nuclei M. Heil, F. Käppeler, E. Uberseder Torino workshop,

Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Neutron capture cross sections on light nuclei M. Heil, F. Käppeler, E. Uberseder Torino workshop,
12C(p,g)13N g III. Nuclear Reaction Rates 12C 13N Nuclear reactions

12C(p,g)13N g III. Nuclear Reaction Rates 12C 13N Nuclear reactions
Reaction rates in the Laboratory Example I: 14 N(p,  ) 15 O stable target  can be measured directly: slowest reaction in the CNO cycle  Controls duration.

Reaction rates in the Laboratory Example I: 14 N(p,  ) 15 O stable target  can be measured directly: slowest reaction in the CNO cycle  Controls duration.
Resonant Reactions The energy range that could be populated in the compound nucleus by capture of the incoming projectile by the target nucleus is for.

Resonant Reactions The energy range that could be populated in the compound nucleus by capture of the incoming projectile by the target nucleus is for.
1 III. Nuclear Reaction Rates Nuclear reactions generate energy create new isotopes and elements Notation for stellar rates: p 12 C 13 N  12 C(p,  )

1 III. Nuclear Reaction Rates Nuclear reactions generate energy create new isotopes and elements Notation for stellar rates: p 12 C 13 N  12 C(p,  )
Outline  Introduction  The Life Cycles of Stars  The Creation of Elements  A History of the Milky Way  Nucleosynthesis since the Beginning of Time.

Outline  Introduction  The Life Cycles of Stars  The Creation of Elements  A History of the Milky Way  Nucleosynthesis since the Beginning of Time.
Joint IAEA-ICTP Workshop on Nuclear Reaction Data for Advanced Reactor Technologies Student’s presentation Calculation of correction factors for neutron.

Joint IAEA-ICTP Workshop on Nuclear Reaction Data for Advanced Reactor Technologies Student’s presentation Calculation of correction factors for neutron.
E.Chiaveri on behalf of the n_TOF Collaboration n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011 Proposal for Experimental Area 2(EAR-2)

E.Chiaveri on behalf of the n_TOF Collaboration n_TOF Collaboration/Collaboration Board Lisbon, 13/15 December 2011 Proposal for Experimental Area 2(EAR-2)
How Old is the Universe? Here are some of the methods,

How Old is the Universe? Here are some of the methods,
1 TCP06 Parksville 8/5/06 Electron capture branching ratios for the nuclear matrix elements in double-beta decay using TITAN ◆ Nuclear matrix elements.

1 TCP06 Parksville 8/5/06 Electron capture branching ratios for the nuclear matrix elements in double-beta decay using TITAN ◆ Nuclear matrix elements.
YET ANOTHER TALK ON BIG BANG NUCLEOSYNTHESIS G. Mangano, INFN Naples STATUS OF BIG BANG NUCLEOSYNTHESIS.

YET ANOTHER TALK ON BIG BANG NUCLEOSYNTHESIS G. Mangano, INFN Naples STATUS OF BIG BANG NUCLEOSYNTHESIS.
J.N. Wilson, EFNUDAT workshop, CERN, August 2010 Level Densities, Decay Probabilities and Cross sections in the Actinide Region J.N. Wilson Institut de.

J.N. Wilson, EFNUDAT workshop, CERN, August 2010 Level Densities, Decay Probabilities and Cross sections in the Actinide Region J.N. Wilson Institut de.
Applications of neutron spectrometry Neutron sources: 1) Reactors 2) Usage of reactions 3) Spallation sources Neutron show: 1) Where atoms are (structure)

Applications of neutron spectrometry Neutron sources: 1) Reactors 2) Usage of reactions 3) Spallation sources Neutron show: 1) Where atoms are (structure)

Similar presentations

Ads by Google