n_TOF-Ph2 The Physics case and the related proposal for measurements at n_TOF for the period A Mengoni CERN, Geneva ENEA, Bologna The CERN n_TOF Facility The CERN n_TOF Facility n_TOF 1-2-3: the physics cases n_TOF 1-2-3: the physics cases Capture studies, fission studies and others Capture studies, fission studies and others Opportunities with a new, shorter flight-path & EAR-2 Opportunities with a new, shorter flight-path & EAR-2 Phase-2 implementation Phase-2 implementation

The n_TOF facility at CERN

The real world n_TOF commissioned in 2002 n_TOF commissioned in

n_TOF basic parameters proton beam momentum 20 GeV/c intensity (dedicated mode) 7 x protons/pulse repetition frequency 1 pulse/2.4s pulse width 6 ns (rms) n/p300 lead target dimensions 80x80x60 cm 3 cooling & moderation material H2OH2OH2OH2O moderator thickness in the exit face 5 cm neutron beam dimension in EAR-1 (capture mode) 2 cm (FWHM)

The real world n_TOF beam characteristics: Neutron intensity and resolution in the full energy range n_TOF beam characteristics: Neutron intensity and resolution in the full energy range 2 nd collimator  =1.8 cm

n_TOF TAC for (n,  ) measurements High detection efficiency: ≈100% (to be compared with 5% of C 6 D 6 or 0.1% of Moxon-Rae) Good energy resolution (direct background suppression mechanisms based on combined multiplicity and energy deposition analysis) n 40 BaF 2 crystals 12 pentagons & 28 hexagons 15 cm crystal thickness Carbon-fiber 10 B-enriched capsules Full Monte Carlo simulations all EM cascades capture events for BG determination The n_TOF Collaboration

Structure mounted in April-04 4  geometry: end of May month commissioning Au(n,  ) & other standards First measurement with a radioactive sample started in August Np(n,  ) sample n_TOF TAC for (n,  ) measurements

Why we do all this?

Objectives of the activity at n_TOF 1.Cross sections relevant for Nuclear Astrophysics 2.Measurements of neutron cross sections relevant for Nuclear Waste Transmutation and related Nuclear Technologies (*) 3.Neutrons as probes for fundamental Nuclear Physics The n_TOF Collaboration (*) contract with the EC (FP5) ended on December

neutrons The canonical s-process ½ of the elements above Fe are produced by the s-process ½ of the elements above Fe are produced by the s-process The astrophysical sites of the s-process are: The astrophysical sites of the s-process are: He burning in intermediate/massive stars He burning in intermediate/massive stars Low-mass AGB’s Low-mass AGB’s There exists a direct correlation between the neutron capture cross section and the abundance (  (n,  ) · N = const. ) There exists a direct correlation between the neutron capture cross section and the abundance (  (n,  ) · N = const. ) The neutron capture cross sections are key ingredients for s-process nucleosynthesis The neutron capture cross sections are key ingredients for s-process nucleosynthesis Nucleosynthesis: the s-process

Nucleosynthesis: the s-process & the r-process residuals N r = N solar - N s

even-even nuclei Neutron capture cross sections: available data

Objectives of the activity at n_TOF 1.Cross sections relevant for Nuclear Astrophysics 2.Measurements of neutron cross sections relevant for Nuclear Waste Transmutation and related Nuclear Technologies (*) 3.Neutrons as probes for fundamental Nuclear Physics The n_TOF Collaboration (*) contract with the EC (FP5) ended on December

Nuclear waste: TRU (1000 MW LWR) 239 Pu: 132 Kg/yr 237 Np: 10.1 Kg/yr 241 Am: 0.5 Kg/yr 243 Am: 2.4 Kg/yr 244 Cm 0.6 Kg/yr LLFP 52.2 Kg/yr

LWR 52 Units Spent fuel 800 t/y Recovered U, Pu 760 t/y REPROCESSING HLW MA: 1t FP: 39t P&T TECHNOLOGIES FINAL DISPOSAL (100 times reduced) Partitioning and Transmutation Yucca Mountain repository would last for 500 yr ! Yucca Mountain repository would last for 500 yr !

Nuclear Data needs for ADS Subcritical reactor core Subcritical reactor core Spallation neutrons: high energies Spallation neutrons: high energies Trasmutation of TRU: exotic fuel Trasmutation of TRU: exotic fuel Zen-ADS Accelerator protons Reactorneutrons

n_TOF experiments The n_TOF Collaboration Target Motivations & Notes 24,25,26 Mg Isotopic abundance ratios in stellar grains. Importance of 22 Ne( ,n) 25 Mg for the s-process neutron balance. Light nuclei, small cross sections. 90,91,92,93,94,96 Zr s-process branching at A=95 & observed abundance patterns in stellar grains. Sensitivity to neutron flux during the s-process. 93 Zr(  1/2 = 1.5 Myr) 139 La Bottleneck in the s-process flow. N=82 neutron shell closure 151 Sm s-process branching at A ≈ Sm is radioactive (  1/2 = 93 yr) 186,187,188 Os Nuclear cosmochronology (Re/Os clock) s-process branching at A ≈ ,206,207,208 Pb 209 Bi Termination of the s-process. Small   /  el Capture 151 Sm 204,206,207,208 Pb, 209 Bi 232 Th 24,25,26 Mg 90,91,92,94,96 Zr, 93 Zr 139 La 186,187,188 Os 233,234 U 237 Np, 240 Pu, 243 Am Fission 233,234,235,236,238 U 232 Th 209 Bi 237 Np 241,243 Am, 245 Cm

n_TOF-Ph2 objectives 1.Cross sections relevant for Nuclear Astrophysics 2.Measurements of neutron cross sections relevant for Nuclear Waste Transmutation and related Nuclear Technologies 3.Neutrons as probes for fundamental Nuclear Physics The n_TOF Collaborationwww.cern.ch/n_TOF

The n_TOF-Ph2 experiments Capture measurements Mo, Ru, Pd stable isotopes Fe, Ni, Zn, and Se (stable isotopes) 79 Se A≈150 (isotopes varii) 234,236 U, 231,233 Pa 235,238 U 239,240,242 Pu, 241,243 Am, 245 Cm r-process residuals calculation isotopic patterns in SiC grains s-process nucleosynthesis in massive stars accurate nuclear data needs for structural materials s-process branching points long-lived fission products Th/U nuclear fuel cycle standards, conventional U/Pu fuel cycle incineration of minor actinides n_TOF-Ph2

Fission measurements MA 235 U(n,f) with p(n,p’) 234 U(n,f) ADS, high-burnup, GEN-IV reactors new 235 U(n,f) cross section standard study of vibrational resonances at the fission barrier Other measurements 147 Sm(n,  ), 67 Zn(n,  ), 99 Ru(n,  ) 58 Ni(n,p), other (n,lcp) Al, V, Cr, Zr, Th, 238 U(n,lcp) He, Ne, Ar, Xe n+D 2 p-process studies gas production in structural materials structural and fuel material for ADS and other advanced nuclear reactors low-energy nuclear recoils (development of gas detectors) neutron-neutron scattering length n_TOF-Ph2 The n_TOF-Ph2 experiments

n_TOF-Ph2 n_TOF target New Experimental Area (EAR-2) The second n_TOF beam line & EAR-2 EAR-1 (at 185 m) ~ 20 m Flight-path length : ~20 m at 90° respect to p-beam direction expected neutron flux enhancement: ~ 100 drastic reduction of the t 0 flash Flight-path length : ~20 m at 90° respect to p-beam direction expected neutron flux enhancement: ~ 100 drastic reduction of the t 0 flash

Improvements (ex: 151 Sm case) sample mass / 3 s/bkgd=1 sample mass / 3 s/bkgd=1 use BaF 2 TAC  x 10 use BaF 2 TAC  x 10 use D 2 O  30 x 5 use D 2 O  30 x 5 use 20 m flight path  30 x 100 use 20 m flight path  30 x 100 consequences for sample mass 50 mg 50 mg 5 mg 5 mg 1 mg 1 mg 10  g 10  g boosts sensitivity by a factor of 5000 ! problems of sample production and safety issues relaxed EAR-2: Optimized sensitivity

Letter of Intent Letter of Intent signed by 24 research labs of the n_TOF Collaboration + 4 newcomers (January 2005) signed by 24 research labs of the n_TOF Collaboration + 4 newcomers (January 2005) n_TOF-Ph2 scientific proposal n_TOF-Ph2 scientific proposal the n_TOF document (September 2004) the n_TOF document (September 2004) CB meeting of February 10-11, 2005 CB meeting of February 10-11, 2005 the n_BANT Symposium (March 2005) the n_BANT Symposium (March 2005) INTC meeting (May 2005) INTC meeting (May 2005) Joint n_TOF/ISOLDE initiative: NuPAC (Nuclear Physics and Astrophysics at CERN)- “Villars CERN promoted by the INTC (October , 2005) Joint n_TOF/ISOLDE initiative: NuPAC (Nuclear Physics and Astrophysics at CERN)- “Villars CERN promoted by the INTC (October , 2005) The n_TOF-Ph2 MoU – end of 2005/beginning of 2006 The n_TOF-Ph2 MoU – end of 2005/beginning of 2006 Road-map towards n_TOF-Ph2 n_TOF-Ph2 : endorsement of the scientific case for Ph2

The n_TOF Collaboration 40 Research Institutions 120 researchers

The End n_TOF-Ph2

Capture studies

n_TOF-Ph2 Capture studies: Mo, Ru, and Pd Motivations: Accurate determination of the r-process abundances (r-process residuals) from observations Accurate determination of the r-process abundances (r-process residuals) from observations SiC grains carry direct information on s-process efficiencies in individual AGB stars. Abundance ratios in SiC grains strongly depend on available capture cross sections data. SiC grains carry direct information on s-process efficiencies in individual AGB stars. Abundance ratios in SiC grains strongly depend on available capture cross sections data.Motivations: Accurate determination of the r-process abundances (r-process residuals) from observations Accurate determination of the r-process abundances (r-process residuals) from observations SiC grains carry direct information on s-process efficiencies in individual AGB stars. Abundance ratios in SiC grains strongly depend on available capture cross sections data. SiC grains carry direct information on s-process efficiencies in individual AGB stars. Abundance ratios in SiC grains strongly depend on available capture cross sections data. N r = N solar - N s

n_TOF-Ph2 n_TOF TAC Setup: The n_TOF TAC in EAR-1 (a few cases with C 6 D 6 if larger neutron scattering) All samples are stable and non-hazardous Metal samples preferable (oxides acceptable) Estimated # of protons x 5x10 16 = sample Capture studies: Mo, Ru, and Pd

n_TOF-Ph2 Capture studies: Fe, Ni, Zn & Se Motivations: Study of the weak s-process component (nucleosynthesis up to A ~ 90) Contribution of massive stars (core He-burning phase) to the s-process nucleosynthesis. Contribution of massive stars (core He-burning phase) to the s-process nucleosynthesis. s-process efficiency due to bottleneck cross sections (Example: 62 Ni) s-process efficiency due to bottleneck cross sections (Example: 62 Ni)Motivations: Study of the weak s-process component (nucleosynthesis up to A ~ 90) Contribution of massive stars (core He-burning phase) to the s-process nucleosynthesis. Contribution of massive stars (core He-burning phase) to the s-process nucleosynthesis. s-process efficiency due to bottleneck cross sections (Example: 62 Ni) s-process efficiency due to bottleneck cross sections (Example: 62 Ni) In addition: Fe and Ni are the most important structural materials for nuclear technologies. Results of previous measurements at n_TOF show that capture rates for light and intermediate-mass isotopes need to be revised. In addition: Fe and Ni are the most important structural materials for nuclear technologies. Results of previous measurements at n_TOF show that capture rates for light and intermediate-mass isotopes need to be revised.

n_TOF-Ph Capture studies: Fe, Ni, Zn & Se The 79 Se case s-process branching: neutron density & temperature conditions for the weak component. s-process branching: neutron density & temperature conditions for the weak component. t 1/2 < 6.5 x 10 4 yr t 1/2 < 6.5 x 10 4 yr The 79 Se case s-process branching: neutron density & temperature conditions for the weak component. s-process branching: neutron density & temperature conditions for the weak component. t 1/2 < 6.5 x 10 4 yr t 1/2 < 6.5 x 10 4 yr

C 6 D 6 Setup: C 6 D 6 in EAR-1 All samples are stable(*) and non-hazardous Metal samples preferable (oxides acceptable) Capture studies: Fe, Ni, Zn & Se (*) except 79 Se n_TOF-Ph2

Capture studies: A ≈ 150 branching isotope in the Sm-Eu-Gd region: test for low-mass TP-AGB accurate branching ratio (capture/  -decay) provides infos on the thermodynamical conditions of the s-processing (if accurate capture rates are known!) Sm Eu Gd 150 Sm 151 Sm 93 a 152 Sm 153 Sm h 154 Sm 151 Eu 152 Eu 9 h 153 Eu 154 Eu 8.8 a 155 Eu a 156 Eu 15.2 d 152 Gd 153 Gd d 154 Gd 155 Gd 156 Gd 157 Gd EAR-2 required EAR-2 required Sample from ISOLDE? Sample from ISOLDE? EAR-2 required EAR-2 required Sample from ISOLDE? Sample from ISOLDE?

Capture studies: actinides Neutron cross section measurements for nuclear waste transmutation and advanced nuclear technologies 241,243 Am The most important neutron poison in the fuels proposed for transmutation scenarios. Build up of Cm isotopes. 239,240,242 Pu (n,  ) and (n,f) with active canning. Build up of Am and Cm isotopes. 245 Cm No data available. 235,238 U Improvement of standard cross sections. 232 Th, 233,234 U 231,233 Pa Th/U advanced nuclear fuels. 233 U fission with active canning. All measurements can be done in EAR-1 (except 241 Am and 233 Pa)

50  m Kapton windows 400  m ISO 2919 Ti canning (400 mg!) + actinide sample air vacuum Neutron absorber Calorimeter  rays Actual setup with thick sample cannings Capture studies: actual TAC setup n_TOF-Ph2

C 12 H 20 O 4 ( 6 Li) 2 Neutron Absorber 10 B loaded Carbon Fibre Capsules Neutron Beam n_TOF-Ph2

Effect of the Ti canning (neutron sensitivity) Capture studies: actual TAC setup

Window surrounded by neutron absorber ( 10 B or 6 Li doped polyethylene) Thin Al backing + actinide sample vacuum Neutron absorber Calorimeter Capture studies: Low neutron sensitivity setup n_TOF-Ph2

Neutron beam Mini Ionisation chamber Stack of with 200  g/cm 2 samples on thin backings Fission Fragments  rays Measurement of capture cross sections of fissile materials (veto) and measurement of the (n,  )/(n,f) ratio. Capture studies: active canning for simultaneous (n,  ) & (n,f) measurements n_TOF-Ph2 << back << back

n_TOF-Ph2 Fission studies

n_TOF-Ph2Beam capture mode (2 mm Ø) Scattering angle 30° Target thickness 250  g/cm 2 Detector radius 20 mm Target-to-detector distance 250 mm Fission studies absolute 235 U(n,f) cross section from (n,p) scattering (n,p) larger or comparable up to 100 MeV H 235 U Neutron energy [MeV]

n_TOF-Ph2 Fission studies FF distributions in vibrational resonances Principles: Time-tag detector for the “start” signal Masses (kinetic energies) of FF from position-sensitive detectors (MICROMEGAS or semiconductors)Principles: Time-tag detector for the “start” signal Masses (kinetic energies) of FF from position-sensitive detectors (MICROMEGAS or semiconductors) << back << back

n_TOF-Ph2 Fission studies cross sections with PPAC detectors: present setup Measurements: 231 Pa(n,f) 231 Pa(n,f) Fission fragments angular distributions (45° tilted targets) for 232 Th, 238 U and other low-activity actinides Fission fragments angular distributions (45° tilted targets) for 232 Th, 238 U and other low-activity actinides EAR-2 boost: measurements of 241,243 Am (in class-A lab) measurements of 241,243 Am (in class-A lab) measurements of 241 Pu and 244 Cm (in class-A lab) measurements of 241 Pu and 244 Cm (in class-A lab)Measurements: 231 Pa(n,f) 231 Pa(n,f) Fission fragments angular distributions (45° tilted targets) for 232 Th, 238 U and other low-activity actinides Fission fragments angular distributions (45° tilted targets) for 232 Th, 238 U and other low-activity actinides EAR-2 boost: measurements of 241,243 Am (in class-A lab) measurements of 241,243 Am (in class-A lab) measurements of 241 Pu and 244 Cm (in class-A lab) measurements of 241 Pu and 244 Cm (in class-A lab) << back << back

n_TOF-Ph2 Fission studies with twin ionization chamber Measurements: FF yields: mass & charge FF yields: mass & charge Test measurement with 235 U then measurements of other MA Test measurement with 235 U then measurements of other MAMeasurements: FF yields: mass & charge FF yields: mass & charge Test measurement with 235 U then measurements of other MA Test measurement with 235 U then measurements of other MA Twin ionization detector with measurement of both FF (PPAC principle) << back << back

n_TOF-Ph2 1.CIC: compensated ion chamber already tested at n_TOF For n_TOF-Ph2: four chambers in the same volume for multi- sample measurements Measurements: 147 Sm(n,  ) (tune up experiment) 147 Sm(n,  ) (tune up experiment) 6 LiF target for calibration EAR-2 boost: 6 LiF target for calibration EAR-2 boost: approx 100 times the ORELA count rate expected approx 100 times the ORELA count rate expected 67 Zn and 99 Ru (n,  ) measurements 67 Zn and 99 Ru (n,  ) measurementsMeasurements: 147 Sm(n,  ) (tune up experiment) 147 Sm(n,  ) (tune up experiment) 6 LiF target for calibration EAR-2 boost: 6 LiF target for calibration EAR-2 boost: approx 100 times the ORELA count rate expected approx 100 times the ORELA count rate expected 67 Zn and 99 Ru (n,  ) measurements 67 Zn and 99 Ru (n,  ) measurements (n,p), (n,  ) & (n,lcp) measurements

n_TOF-Ph2 2.MICROMEGAS already used for measurements of nuclear recoils at n_TOF For n_TOF-Ph2: converter replaced by sample expected count rate: 1 reaction/pulse (  =200 mb, Ø=5cm, 1  m thick) (n,p), (n,  ) & (n,lcp) measurements << back << back

n_TOF-Ph2 (n,p), (n,  ) & (n,lcp) measurements 3.Scattering chambers with  E-E or  E-  E-E telescopes Measurements: 56 Fe and 208 Pb (tune up experiment) 56 Fe and 208 Pb (tune up experiment) Al, V, Cr, Zr, Th, and 238 U Al, V, Cr, Zr, Th, and 238 U a few x protons/sample in fission mode a few x protons/sample in fission modeMeasurements: 56 Fe and 208 Pb (tune up experiment) 56 Fe and 208 Pb (tune up experiment) Al, V, Cr, Zr, Th, and 238 U Al, V, Cr, Zr, Th, and 238 U a few x protons/sample in fission mode a few x protons/sample in fission mode Setup: in parallel with fission detectors production cross sections  (E n ) for (n,xc) c = p, , d differential cross sections d  /d , d  /dE << back << back

n_TOF-Ph2 Neutron scattering reactions Neutron incident energy 30 – 75 MeV in 2.5 MeV bins Kiematic locus of the n + 2 H  n + p + n reaction for: E n = 50 MeV Θ n = 20º, Φ n = 0º Θ p = 50º, Φ p = 180º << back << back Direct n + n scattering experiment not feasible! Alternatively, interaction of two neutrons in the final state of a nuclear reaction. Examples of such reactions are:  H  n + n +   H  n + n +  n + 2 H  n + n + p n + 2 H  n + n + p

n_TOF-Ph2 << back << back