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(Once again) The n_TOF-Ph2 neutron fluence 2009-2011

(Once again) The n_TOF-Ph2 neutron fluence 2009-2011 C. Guerrero (CERN), M. Barbagallo (INFN/Bari), A. Tsinganis (CERN), N. Colona (INFN/Bari), E Mendoza (CIEMAT) et al. n_TOF Annual Meeting, Lisbon 13-16 December 2011. Measurements of the n_TOF neutron fluence: 2009-2011. 182.2 m. 183.25 m.

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(Once again) The n_TOF-Ph2 neutron fluence 2009-2011

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  1. (Once again) The n_TOF-Ph2 neutron fluence 2009-2011 C. Guerrero (CERN), M. Barbagallo (INFN/Bari), A. Tsinganis (CERN), N. Colona (INFN/Bari), E Mendoza (CIEMAT) et al. n_TOF Annual Meeting, Lisbon 13-16 December 2011

  2. Measurements of the n_TOF neutron fluence: 2009-2011 182.2 m 183.25 m 182.9 m 60 mm Ta windows (0.15mm) Ta electrodes (0.125mm) Air (7 cm) Air (20 cm) MGAS (30 cm) [ONLY IN 2009] Ar (1 atm) 45 cm Ar (1 atm) n B U Li Pt electrodes (0.125mm) 235U samples (444 mg/cm2 (total 201.4 mg in 76 mm diameter deposits) Al window (500mm) Kapton windows (50 mm each ) Li = Mylar (1.5mm, 1.4 g/cm3) + C (0.045 mm, 2.15 g/cm3) + 6Li (6 mm, 0.5 g/cm3) + C (0.045 mm, 2.15 g/cm3) B = Kapton (25mm,1.42 g/cm3) + Cu(2mm,8.94 g/cm3) + 10B4C (2mm,2.52g/cm3) + Cu (5mm,8.94 g/cm3) + Kapton (25mm,1.42 g/cm3) + Cu (5mm,8.94 g/cm3) U = Al(20mm,2.7 g/cm3) + 235UF4(0.47mm,6.7 g/cm3) + Cu (5mm,8.94g/cm3 )+ Kapton (50mm , 1.42g/cm3) + Cu(5mm,8.94 g/cm3) 2009: SiMon + PTB 2010: SiMon+PTB+MGAS(235U,10B) 2011: SiMon+MGAS(235U,10B)

  3. Sizable transmission through SiMon and MGAS Detailed MCNP simulations by Emilio Mendoza (CIEMAT) [CERN/CDS: n_TOF-INT-2011-001] TWO evaluated fluence given: @SiMon: neutron arriving to the EAR-1 @sample: after passing through 6Li, Al, 10B and 235U

  4. MGAS-10B: Selection cuts and Hi-En limit 1-100 eV 0.1-1 keV 1-10 keV 10-30 keV 30-100 keV 100-300 keV Selection cut: MGASamp > 62.5 + 5.277e-5*En + 3.83e11*En2 300-500 keV

  5. MGAS-10B: detection efficiency MGAS sees only those a’s emitted FORWARD Angular distribution has an effect!! F. J. Hambsch, I. Ruskov, Nucl. Sc. and Eng. 163 1 (2009) 1-16 “The 10B(n,0)7Li and 10B(n,1)7Li Alpha-Particle Angular Distributions for En < 1 MeV” Efficiency calculated as ratio of forward to background emission prob. 9%

  6. SiMon: Selection cuts and Hi-En limit Amplitude cut depends on the neutron energy 10-100 eV 100-1000 eV 1-10 keV 10-100 keV 100-300 keV 300-500 keV Because of Ang. Distr., efficiency depends also on neutron energy (large correction above 10-20 keV)

  7. Comparison MGAS(10B) & SiMon (6Li) [2010-2011] Data from SiMon and MGAS(10B) are always in good agreement: Always combined together However: MGAS(10B) [2010] SiMon(6Li) [2010] MGAS(10B) [2011] SiMon(6Li) [2011] Slower electronics → Worse timing → Smoothing of structures

  8. Comparison MGAS(10B) & SiMon (6Li) [2010-2011] Data from SiMon and MGAS(10B) are always in good agreement: Always combined together However: ±3%

  9. Available data and fluence evaluation strategy ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Thermal: All measurements used (normalized to PTB[235U]) ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Thermal to 100 keV: 6Li and 10B cross sections: standard (and smooth) cross sections! 235U cross section: non standard + non-smooth URR SiMon & MGAS(10B) in good agreement [MGAS-2010 too slow: not used above few keV] ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- PTB becomes compatible again with SiMon & MGAS around 40-50 keV: the differences between PTB and the rest suggest that 235U s(n,f) is overestimated by as much as 10% between 10-30 keV. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 100keV -10 MeV 235U cross section: standard (and smooth) SiMon & MGAS start to suffer from Hi-En effects [difficult separation in amplitude spectrum] FLUKA+MCNP simulation available for helping resolve the Al dips (normalized at 10 keV) -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

  10. The evaluated neutron fluence (2009-2011) [100 bins/decade] 2009 2010 2011 Statistical Systematic (RMS) 2% 5% 3-4% 2.5%

  11. The evaluated neutron fluence (2009-2011) : comparison to MC Measured [100 bpd] FLUKA+MCNP [600bpd]

  12. The evaluated neutron fluence (2009-2011) : comparison to MC Measured [100 bpd] FLUKA+MCNP [600bpd] +5% -4% +12% +10%

  13. Conclusions n_TOF-Ph2 neutron fluence fully analyzed for 2009, 2010 and 2011. EVALUATION STRATEGY: SiMon and MGAS-B10 used where below 100 keV (standard cross sections) PTB used at thermal and above 100 keV UNCERTAINTIES Statistical uncertainty: 0.2-4% (<2% up to 100 keV, always ≤ systematic uncertainty) Systematic uncertainty: <2% En<1 keV ~2.5% 1-8 keV ~5% 8-80 keV ~3-4% 0.08 It is worth investigating in other facilities the discrepancy found in 235U s(n,f) @ 10-50 keV? FLUKA+MCNP simulations ready and “compatible” with measured flux @thermal and above 10 keV • PRACTICAL TIPS: • Neutron energy calculated from TOF and Dl(E) [recursive routine] • ROOT files available in: • /afs/cern.ch/user/c/cguerrer/public/fluence/nTOF-Ph2_fluence_2009-2011_6Dec2011.root • hNFluenceEVALUATED20XX [after 6Li, Al, 10B and 235U] • hNFluenceEVALUATED20XXatSiMon [@SiMon]

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