C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 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

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

Ta electrodes (0.125mm)

Pt electrodes (0.125mm) 235U samples (444 mg/cm2 (total 201.4 mg in 76 mm diameter deposits)

Ta windows (0.15mm)60 mm

Al window (500mm)

B U

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)

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)

Li

Kapton windows (50 mm each )

182.2 m 182.9 m 183.25 m

Air (7 cm)

Air (20 cm)

Ar (1 atm)

Ar (1 atm)

n

MGAS (30 cm) [ONLY IN 2009]45 cm

Measurements of the n_TOF neutron fluence: 2009-2011

2009: SiMon + PTB 2010: SiMon+PTB+MGAS(235U,10B) 2011: SiMon+MGAS(235U,10B)

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

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

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

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

300-500 keV

Selection cut:MGASamp > 62.5 + 5.277e-5*En + 3.83e11*En

2

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

MGAS sees only those a’s emitted FORWARD

Angular distribution has an effect!!

MGAS-10B: detection efficiency

9%

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.

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

SiMon: Selection cuts and Hi-En limit

10-100 eV100-1000 eV1-10 keV10-100 keV100-300 keV300-500 keV

Amplitude cut depends on the neutron energy

Because of Ang. Distr., efficiency depends also on neutron energy

(large correction above 10-20 keV)

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

Comparison MGAS(10B) & SiMon (6Li) [2010-2011]

MGAS(10B) [2010]SiMon(6Li) [2010]MGAS(10B) [2011]SiMon(6Li) [2011]

Slower electronics → Worse timing → Smoothing of structures

Data from SiMon and MGAS(10B) are always in good agreement: Always combined together

However:

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

±3%

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

However:

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

Available data and fluence evaluation strategy

2009 2010 20110.025-0.3 eV Sili09 + PTB09 Sili10 + PTB10 + MGAS10 Sili10 + MGAS100.3-100 eV Sili-09 Sili10 + MGAS10 Sili11 + MGAS11100-500 eV Sili-09 Sili10 + MAS10 + Sili11 + MGAS110.5-100 keV Sili-09 + Sili10 + MAS10 + Sili11 + MGAS110.1-1 MeV PTB09 + PTB101-10 MeV PTB10

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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]

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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.-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

100 keV -10 MeV235U 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)

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C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

The evaluated neutron fluence (2009-2011) [100 bins/decade]

200920102011

StatisticalSystematic (RMS)

2% 2.5% 5% 3-4%

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

The evaluated neutron fluence (2009-2011) : comparison to MC

Measured [100 bpd]FLUKA+MCNP [600bpd]

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

The evaluated neutron fluence (2009-2011) : comparison to MC

+10%

+12%

+5%-4%

Measured [100 bpd]FLUKA+MCNP [600bpd]

C. Guerrero “The n_TOF-Ph2 neutron fluence: 2009-2011”

n_TOF Annual Meeting, Lisbon 13-16 December 2011

Conclusionsn_TOF-Ph2 neutron fluence fully analyzed for 2009, 2010 and 2011.

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]

FLUKA+MCNP simulations ready and “compatible” with measured flux @thermal and above 10 keV

EVALUATION STRATEGY:SiMon and MGAS-B10 used where below 100 keV (standard cross sections)PTB used at thermal and above 100 keV

UNCERTAINTIESStatistical 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?