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The Future of the n_TOF Facility: Physics Case and Proposal for Measurements

This article discusses the physics case for the activities at the n_TOF facility at CERN, including plans for measurements in Phase-2 and opportunities with a new shorter flight-path. It also highlights the objectives of the activity at n_TOF, which includes measurements of neutron cross sections relevant for nuclear astrophysics, nuclear waste transmutation, and nuclear technologies. Additionally, it examines the role of neutrons as probes for fundamental nuclear physics.

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The Future of the n_TOF Facility: Physics Case and Proposal for Measurements

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  1. The Future of/at n_TOFThe physics case and the related proposal for measurements at n_TOF for 2006 and beyond A MengoniIAEA, Vienna • the CERN n_TOF Facility • the physics case for the activities at n_TOF • plan for measurements in Phase-2 • opportunities with a new, shorter flight-path: EAR-2 www.cern.ch/n_TOF

  2. The n_TOF facility at CERN www.cern.ch/n_TOF

  3. sample June 2004 n_TOF • n_TOF commissionedin 2002 www.cern.ch/n_TOF

  4. n_TOF basic parameters www.cern.ch/n_TOF

  5. The neutron flux 2nd collimator =1.8 cm Performance Report CERN-INTC-2002-037, January 2003 CERN-SL-2002-053 ECT

  6. World scene for tof measurements n_TOF-Ph2

  7. 232Th(n,g): n_TOF & GELINA Source: L Leal, IAEA CRP meeting, December 2004

  8. 237Np(n,g) at LANSCE Preliminary (Analysis by E.I. Esch and R. Reifarth) Source: J Ullman, n_BANT workshop, CERN, March 2005

  9. 237Np(n,g) at LANSCE Preliminary (Analysis by E.I. Esch and R. Reifarth) Source: J Ullman, n_BANT workshop, CERN, March 2005

  10. 237Np(n,g) at n_TOF www.cern.ch/n_TOF The n_TOF Collaboration

  11. Uniqueness of n_TOF • Combines: • Highest instantaneous intensity neutron source worldwide at a 185 m flight path used in TOF cross section measurements • Excellent energy resolution • Innovative data Acquisition system based on flash ADCs (2 Tbytes/day via CERN CASTOR system) • Latest generation of detectors and beam monitors: • (n,g): ultra low neutron sensitivity C6D6 detectors, high performance Total Absorption Calorimeter • (n,f): Low background PPAC setup, FIC detector • Beam monitors: redundant 197Au(n,g), 6Li(n,a)t, 235U(n,f) monitors • Fully characterized facility for neutron cross section measurements • Best facility for: radioactive, rare, low cross section samples and high energy measurements

  12. Objectives of the activity at n_TOF • Cross sections relevant for Nuclear Astrophysics • Measurements of neutron cross sections relevant for Nuclear Waste Transmutation and related Nuclear Technologies • Neutrons as probes for fundamental Nuclear Physics www.cern.ch/n_TOF The n_TOF Collaboration

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

  14. Nucleosynthesis: the s-process &the r-process residuals Nr= Nsolar - Ns www.cern.ch/n_TOF The n_TOF Collaboration

  15. Objectives of the activity at n_TOF • Cross sections relevant for Nuclear Astrophysics • Measurements of neutron cross sections relevant for Nuclear Waste Transmutation and related Nuclear Technologies(*) • Neutrons as probes for fundamental Nuclear Physics (*) contract with the EC within the FP5 www.cern.ch/n_TOF The n_TOF Collaboration

  16. Sustainable nuclear energy or its phase-out ? Expansion of electricity needs (in particular in developing countries) & Concern about CO2 emission level The nuclear power option will only be exercised, however, if the technology demonstrates better economics, improved safety, successful waste management, and low proliferation risk, and if public policies place a significant value on electricity production that does not produce CO2. (from the MIT report, 2003)

  17. Nuclear waste (1000 MWe LWR) 244Cm 1.5 Kg/yr 241Am:11.6 Kg/yr 243Am: 4.8 Kg/yr 239Pu: 125 Kg/yr (plus: 240,242,244Pu) 237Np: 16 Kg/yr LLFP 76.2 Kg/yr LLFP source: Actinide and Fission Product Partitioning and Transmutation – NEA (1999)

  18. Th/U fuel cycle www.cern.ch/n_TOF

  19. Capture 151Sm 204,206,207,208Pb, 209Bi 232Th 24,25,26Mg 90,91,92,94,96Zr, 93Zr 139La 186,187,188Os 233,234U 237Np,240Pu,243Am Fission 235,238U, 234U, 233,236U 232Th 209Bi 237Np 241,243Am, 245Cm n_TOF experiments 2002-4 • Cross sections relevant for Nuclear Astrophysics • Measurements of neutron cross sections relevant for Nuclear Waste Transmutation and related Nuclear Technologies • Neutrons as probes for fundamental Nuclear Physics The n_TOF Collaboration

  20. Capture 151Sm 204,206,207,208Pb, 209Bi 232Th 24,25,26Mg 90,91,92,94,96Zr, 93Zr 139La 186,187,188Os 233,234U 237Np,240Pu,243Am Fission 235,238U, 234U, 233,236U 232Th 209Bi 237Np 241,243Am, 245Cm n_TOF experiments 2002-4 data analysis completed (14/36) NOTE: TAC started operation in July 2004 All docs on: www.cern.ch/n_TOF The n_TOF Collaboration

  21. Capture 151Sm 204,206,207,208Pb, 209Bi 232Th 24,25,26Mg 90,91,92,94,96Zr, 93Zr 139La 186,187,188Os 233,234U 237Np,240Pu,243Am Fission 235,238U, 234U, 233,236U 232Th 209Bi 237Np 241,243Am, 245Cm n_TOF experiments U Abbondanno et al. - The n_TOF Collaboration Phys. Rev. Lett. 93 (2004), 161103 n_TOF MACS-30 = 3100 ± 160 mb <D0> = 1.48 ± 0.04 eV, S0 = (3.87 ± 0.20)×10-4 The n_TOF Collaboration

  22. 152Gd 153Gd 154Gd 155Gd 156Gd 157Gd Gd Eu 151Eu 152Eu 153Eu 154Eu 155Eu 156Eu 150Sm 151Sm 93 a 152Sm 153Sm 154Sm Sm Capture 151Sm 204,206,207,208Pb, 209Bi 232Th 24,25,26Mg 90,91,92,94,96Zr, 93Zr 139La 186,187,188Os 233,234U 237Np,240Pu,243Am Fission 235,238U, 234U, 233,236U 232Th 209Bi 237Np 241,243Am, 245Cm n_TOF experiments U Abbondanno et al. - The n_TOF Collaboration Phys. Rev. Lett. 93 (2004), 161103 • T8 > 4 using the “classical” s-process model • from AGB modeling: 71% of 152Gd Present main uncertainty: lb(T) of 151Sm The n_TOF Collaboration

  23. Capture 151Sm 204,206,207,208Pb, 209Bi 232Th 24,25,26Mg 90,91,92,94,96Zr, 93Zr 139La 186,187,188Os 233,234U 237Np,240Pu, 243Am Fission 235,238U, 234U, 233,236U 232Th 209Bi 237Np 241,243Am, 245Cm n_TOF experiments 243Am(n,g) Measurement performed in September 2004 1) Room + target frame background 2) Background from Ti canning + 1) 3) 10 mg of 243Am + 2) First 243Am(n,g) measurement EVERsample: 10 mg, 185 MBq activity The n_TOF Collaboration

  24. Capture 151Sm 204,206,207,208Pb, 209Bi 232Th 24,25,26Mg 90,91,92,94,96Zr, 93Zr 139La 186,187,188Os 233,234U 237Np,240Pu,243Am Fission 235,238U, 234U, 233,236U 232Th 209Bi 237Np 241,243Am, 245Cm n_TOF experiments PPACs & FIC-0 (2003) 234U(n,f) An unprecedent wide energy range can be explored at n_TOF in a single experiment The n_TOF Collaboration

  25. Capture 151Sm 204,206,207,208Pb, 209Bi 232Th 24,25,26Mg 90,91,92,94,96Zr, 93Zr 139La 186,187,188Os 233,234U 237Np,240Pu,243Am Fission 235,238U, 234U, 233,236U 232Th 209Bi 237Np 241,243Am, 245Cm n_TOF experiments FIC-1 (2003) 236U(n,f) The very high resolution of the n_TOF installation allows for studing fine neutron resonance structure The n_TOF Collaboration

  26. Capture 151Sm 204,206,207,208Pb, 209Bi 232Th 24,25,26Mg 90,91,92,94,96Zr, 93Zr 139La 186,187,188Os 233,234U 237Np,240Pu,243Am Fission 235,238U, 234U, 233,236U 232Th 209Bi 237Np 241,243Am, 245Cm n_TOF experiments FIC-1 (2003) 237Np(n,f) The very high resolution of the n_TOF installation allows for studing fine neutron resonance structure The n_TOF Collaboration

  27. n_TOF-Ph2 objectives • Cross sections relevant for Nuclear Astrophysics • Measurements of neutron cross sections relevant for Nuclear Waste Transmutation and related Nuclear Technologies • Neutrons as probes for fundamental Nuclear Physics n_TOF-Ph2 www.cern.ch/n_TOF

  28. The n_TOF-Ph2 experiments In 2006 : (a) all stable Ni isotopes + 63Ni (b) 236U, 238U n_TOF-Ph2 www.cern.ch/n_TOF

  29. The n_TOF-Ph2 experiments n_TOF-Ph2 www.cern.ch/n_TOF

  30. n_TOF (Phase-1) financial scheme n_TOF-Ph2 www.cern.ch/n_TOF

  31. n_TOF-Ph2: basic startup funds n_TOF-Ph2 www.cern.ch/n_TOF

  32. The second n_TOF beam line & EAR-2 NewExperimentalArea (EAR-2) ~ 20 m n_TOF target EAR-1 (at 185 m) Flight-path length : ~20 m at 90° respect to p-beam direction expected neutron flux enhancement: ~ 100 drastic reduction of the t0 flash n_TOF-Ph2 www.cern.ch/n_TOF

  33. problems of sample production and safety issues relaxed EAR-2: Optimized sensitivity consequences for sample mass • 50 mg • 5 mg • 1 mg • 10 mg Improvements (ex: 151Sm case) • sample mass / 3 s/bkgd=1 • use BaF2 TAC e x 10 • use D2O F30 x 5 • use 20 m flight path F30 x 100 boosts sensitivity by a factor of 5000 ! (a factor of 100 ONLY from flux boost) n_TOF-Ph2 www.cern.ch/n_TOF

  34. Road-map towards n_TOF-Ph2 • Letter of Intent • signed by 24 research labs of the n_TOF Collaboration + 4 newcomers(January 2005) • n_TOF-Ph2 scientific proposal • the n_TOF 1-2-3 document (September 2004) • CB meeting of February 10-11, 2005 • the n_BANT Symposium (March 2005) • Proposal presented to the INTC (May 2005) • NuPAC (Nuclear Physics and Astrophysics at CERN), October 10-12, 2005 • The n_TOF-Ph2 MoU – end of 2005/beginning of 2006 n_TOF-Ph2 www.cern.ch/n_TOF

  35. The n_TOF Collaboration 41 Research Groups 120 researchers www.cern.ch/n_TOF

  36. Conclusions • n_TOF is a facility with unique characteristics for x-section measurements on: • radioactive samples • rare isotopes • isotopes with small cross sections • in wide energy range (in particular at high energies) • n_TOF just started to operate, providing best world results in several cases • Still large campaigns are needed to exploit its capabilities in the present configuration • A new plan for measurements has been elaborated for 2006 and beyond • The additional beam line (EAR-2) could boost the facility performances much beyond any presently available installations n_TOF-Ph2 www.cern.ch/n_TOF

  37. The End n_TOF-Ph2 www.cern.ch/n_TOF

  38. Capture studies n_TOF-Ph2

  39. Capture studies: Mo, Ru, and Pd • Motivations: • 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. Nr= Nsolar - Ns n_TOF-Ph2

  40. Capture studies: Mo, Ru, and Pd sample • Setup: The n_TOF TAC in EAR-1 (a few cases with C6D6 if larger neutron scattering) • All samples are stable and non-hazardous • Metal samples preferable (oxides acceptable) << back Estimated # of protons 20 x 5x1016 = 1018 n_TOF-Ph2

  41. Capture studies: Fe, Ni, Zn and 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. • s-process efficiency due to bottleneck cross sections (Example: 62Ni) 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-Ph2

  42. Capture studies: Fe, Ni, Zn and Se 34 32 30 38 40 42 44 46 48 50 • The 79Se case • s-process branching: neutron density & temperature conditions for the weak component. • t1/2 < 6.5 x 104 yr << back n_TOF-Ph2

  43. Capture studies: Fe, Ni, Zn and Se • Setup: C6D6 in EAR-1 • All samples are stable(*) and non-hazardous • Metal samples preferable (oxides acceptable) << back (*) except 79Se n_TOF-Ph2

  44. Capture studies: A ≈ 150 152Gd 153Gd 239.47 d 154Gd 155Gd 156Gd 157Gd Gd Eu 151Eu 152Eu 9 h 153Eu 154Eu 8.8 a 155Eu 4.761 a 156Eu 15.2 d 150Sm 151Sm93 a 152Sm 153Sm 42.27 h 154Sm Sm • EAR-2 required • Sample from ISOLDE? • branching isotope in the Sm-Eu-Gd region: • test for low-mass TP-AGB • branching ratio (capture/b-decay) provides infos on the thermodynamical conditions of the s-processing (if accurate capture rates are known!) << back n_TOF-Ph2

  45. Capture studies: actinides Neutron cross section measurements for nuclear waste transmutation and advanced nuclear technologies All measurements can be done in EAR-1 (except 233Pa) << back

  46. Capture studies: actual TAC setup Actual setup with thick sample cannings g rays 400mm ISO 2919 Ti canning (400 mg!) + actinide sample air vacuum 50mm Kapton windows Neutron absorber Calorimeter << back n_TOF-Ph2

  47. Neutron Beam C12H20O4(6Li)2 Neutron Absorber 10B loaded Carbon Fibre Capsules << back n_TOF-Ph2

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

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

  50. Capture studies: active canning for simultaneous (n,g) & (n,f) measurements Stack of with 200 mg/cm2 samples on thin backings g rays Neutron beam Fission Fragments Mini Ionisation chamber << back Measurement of capture cross sections of fissile materials (veto) and measurement of the (n,g)/(n,f) ratio. n_TOF-Ph2

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