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(Once again) The n_TOF-Ph2 neutron fluence (2010) C. Guerrero (CERN), M. Barbagallo (INFN/Bari), A. Tsinganis (CERN), N. Colona (INFN/Bari), E Mendoza (CIEMAT) et al. Situation in the last meeting (April 2011) and plan.

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slide1

(Once again) The n_TOF-Ph2 neutron fluence (2010)

C. Guerrero (CERN), M. Barbagallo (INFN/Bari), A. Tsinganis (CERN),

N. Colona (INFN/Bari), E Mendoza (CIEMAT) et al.

slide2

Situation in the last meeting (April 2011) and plan

  • SiMon and MGAS-B10 seem to be in good agreements up to at least 10 keV.
  • High energy limit for SiMon and MGAS-B10 not clear.
  • Analysis conditions (amp. cuts) to be studied in detail.
  • (PTB+MGAS-U5) in 6-9% disagreement wrt (SiMon+MGAS-B10) in ~7-100 keV
  • FLUKA+MCNP simulation in overall agreement with data, except in the Al dips and above ~600 keV (~5% difference)
  • […]

Review the full analysis

-Transmission through material along the beam.

- Analysis conditions for the analysis of each detector

- Detection efficiency dependence with En of each detector

- Identify high energy limit of each detector

- Corrections from transmission through the material along the beam

- Correction of t0 for TOF/En conversion

Complete FLUKA+MCNP simulations

slide3

Expected reaction yield (transmission ≠ 1)

Detailed MCNP simulations by Emilio Mendoza (CIEMAT) [n_TOF-INT-2011-001]

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)

slide5

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

slide6

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%

slide7

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

(very large correction above 10-20 keV)

slide9

Summary and strategy

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Thermal

All measurements normalized to PTB (235U)

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Below 25 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

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

25 -150 keV

235U cross section: Point-wise without resonant/interference effects

SiMon has larger uncertainty due to Ang. Distr. (but it is in better agreement with PTB than MGAS)

FLUKA+MCNP simulation available for helping resolve the Al dips (normalized at 10 keV)

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

150-250 keV

235U, 6Li and 10B cross sections: standard.

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Above 250 keV

Both SiMon and MGAS start having problems (statistics, g-flash, recoils,…)

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

slide15

Actually, it is not so nice.....

Main open questions are:

PTB disagrees ~8-25 keV (10%)

Simulation disagrees ~1-10 keV (5%)

MGAS dips too “small”! (10-20%)

TOF/E relation pending!

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