Simulation of the 7Li(p,n) quasi-monoenergetic neutron source at NPI/ Řež

Size: px

Start display at page:

Download "Simulation of the 7Li(p,n) quasi-monoenergetic neutron source at NPI/ Řež"

Brianne Welch
6 years ago
Views:

1 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Nuclear Physics Institute Řež, near Prague Simulation of the 7Li(p,n) quasi-monoenergetic neutron source at NPI/ Řež S.P. Simakov, U. Fischer Institute of Nuclear Physics and Reactor Technology Forschungszentrum Karlsruhe, Germany P. Bém, M. Honusek, M. Götz, J. Novák and E. Šimečková 2) Nuclear Physics Institute, Řež, Czech Republic Workshop on Activation Data EAF 2009, Prague, March 2009

2 Computational Tools and Data for Li neutron Simulations up to 50 MeV Neutron production and transport calculation: MCNPX, version 2.5 Cross sections files and models for (p,xn) reactions on light nuclei: Lithium-7 as a neutron source: E threshold = 1.88 MeV for 7 Li(p,n 0 ) 7 Be(g.s.) = 2.38 MeV for 7 Li(p,n 1 ) 7 Be(1st level = 0.43 MeV) = 3.70 MeV for 3-body breakup 7 Li(p,n 3 He) 4 He = 7.70 MeV for 7 Li(p,n 2 ) 7 Be(2nd level = 4.55 MeV) =. LA-150h proton cross sections library T 1/2 = days ε+ (100%) 7 Li + γ (478keV,10.5%) Carbon as a proton beam stopper and parasitic neutron source: 12 C abundance 98.9% 13 C abundance 1.1% 12 C(p,n), E th = 19.6 MeV 13 C(p,n), E th = 3.2 MeV LA-150h library MCNPX in-build model March 2009, Prague Workshop on Activation Data EAF

3 Monoenergetic Neutron Sources employing Li(p,n) reaction Laboratory Neutron Energy, MeV Li thickness, mm Proton current, μa Reference With proton beam deflection magnet Louvain Univ., NIM A421 (1999) 284 Belgium TIARA, NIM A428 (1998) 454 Japan Uppsala Univ. Sweden ? NIM B241 (2005) 419 Without deflection magnet, 2 cm thick C proton beam stopper behind Li target CYRIC, ? NIM A389 (1997) 463 Japan NPI/Řež, Czech < P. Bĕm et al. For activation measurements the thin Li plate and thick C stopper looks more preferable than deflecting magnet, since the activation foil could be located closer to the neutron source, but how many parasitic neutrons does C(p,xn) reaction produce? March 2009, Prague Workshop on Activation Data EAF

4 Li/C Neutron Source at CYRIC, Tohoku University /Y. Uwamino et al., NIM A389(1997)463/ Target set-up: - 2 mm thick 7Li - 12 mm thick carbon stopper Neutron Spectra measurement: - Proton Energies = MeV - TOF technique - NE 213 scintillator at 12 m - p-beam charge and Be-7 activity in Li foil were measured to find the absolute n-flux March 2009, Prague Workshop on Activation Data EAF

5 Validation of MCNPX calculations against CYRIC data Energy Differential Neutron Yield Neutron Flux (θ = 0 o ), n/mev/sr/μc Li/C+p(40MeV) Li/C + protons (E p = 40 MeV), Θ n = 0 o thick C +p(39.2mev) nat C+p(39.2 MeV) 12 C(p,xn) 7 Li+p(40MeV) 13 C(p,xn) Neutron Energy, MeV Neutron Peak (38.3MeV) Intensity at forward angle: Ep Peak(0 o ), n/sr/μc MeV Experiment MCNPX 40 (1.6±0.2)E E+9 MCNPX/LA-150h reasonable reproduces CYRIC neutron source spectrum and thick carbon neutron yield March 2009, Prague Workshop on Activation Data EAF

MCNPX: Li-foil, C-stop, Cooling media (spirit), Target support, Bi-foils (15mm dia. 0.

6 p + 7 Li neutron source experimental set-up and MCNPX model 88 mm 48 mm Li-foil p-beam C-stop Bi-foils C 2 H 5 OH SS+C 2 H 5 OH Al SS The details of the set-up simulated in MCNPX: Li-foil, C-stop, Cooling media (spirit), Target support, Bi-foils (15mm dia. 0.5 mm thick) with SS/Al holder March 2009, Prague Workshop on Activation Data EAF

7 Neutron Flux average over Bi-foil volume (ø15 by 0.5 mm) Energy differential Fluxes (X = 48 & 88 mm) at E p =36.5 MeV Neutron Flux, n/cm 2 /MeV/μC Li+ Target Assembly, E p = 36.5 MeV Flux in Bi foil dia 15mm at distance X X=48 mm 7 Li(p,xn)+Assembly X=88 mm 7 Li(p,xn)+Assembly 7 Li(p,xn) 7 Li(p,xn) Neutron Energy, MeV Energy integrated Fluxes [n/cm 2 /μc] at X=48 mm and E p =36.5 MeV Total Mono Energy Peak Other Energies 7 Li + Assembly 3.39 E E+8 (22%) 2.66 E+8 (78%) only 7 Li 1.90 E E+8 (41%) 1.12 E+8 (59%) Ratio March 2009, Prague Workshop on Activation Data EAF

8 Neutron Yield(E,Θ), n/mev/sr/μc Neutron Flux and Spectra vs. Emission Angle (only 7Li foil) Energy differential Yields vs. Angles E p = 36.5 MeV + 7 Li (2mm) Θ = 0 o Θ = 10 o Θ = 20 o Θ = 30 o Neutron Energy, MeV Foil ø15 mm at 48 mm from source subtends a cone with opening Angle = ± 9 o This results to the Variation of - Flux by factor Energy by 0.14 MeV (ΔEp in 2mm Li = ± 0.75 MeV) Total and mono-energy Peak Yields vs. Angles March 2009, Prague Workshop on Activation Data EAF Neutron Yield(Θ), n/sr/μc MonoPeak/Total E p = 36.5 MeV + 7 Li Mono Energy Peak Total Yield Emission Angle, degrees

9 C/E for induced radio-activities in Bi at E p = 36.5 MeV or E n = 34.1 MeV 6 C/E Bi Activation (19.7 h), E p = 36.5MeV Foil at X = 88mm Foil at X = 48 mm EAF (n,5n)bi-205 (n,4n)bi-206 (n,3n)bi-207 Radioactive Inventories March 2009, Prague Workshop on Activation Data EAF

10 209 Bi(n,5n) 205 Bi reaction cross section (E threshold = MeV) Cross Section and Flux vs. Neutron Energy Reaction Cross Section, b Bi(n,5n) 205 Bi JAERI'98 n-flux IEAF-2001 EAF-2007 ENDF/B-VII NPI/Rez' Neutron Energy, MeV Energy Flux, n/cm 2 /s/mev C/E Ratio for Radio-activity C/E = 5.03 at X= 48 mm C/E = 4.29 at X= 88 mm <C/E> = 4.66 ± 0.37(8%) Extracted Experim. Cross Section En n-flux σ(eaf2007), barns MeV n/cm2 original original/<c/e> E E E-2 ± 8% E E E-2 ± 8% E March 2009, Prague Workshop on Activation Data EAF

11 209 Bi(n,3n) 207 Bi reaction cross section (E threshold = MeV) Cross Section, Flux and their Product Cumulative Sum vs. Neutron Energy Cross Section, b x Bi(n,3n) 207 Bi LANL'77 ENDF/B-VII Σ Ε F(E)σ(E) 0 JAERI'98 EAF-2007 n-flux IEAF x Neutron Energy, MeV Energy Flux, n/cm 2 /s/mev C/E Ratio for Radio-activity and energy Groups contribution C/E = 0.78 at X= 48 mm C/E = 0.76 at X= 88 mm <C/E> = 0.77 ± 0.01 (1.3%) two mono energy groups (33 to 35 MeV) contribute 50% others energy groups (13.8 to 35 MeV) contribute 50% March 2009, Prague Workshop on Activation Data EAF

12 Conclusions MCNPX and LA-150h evaluation for 7 Li(p,n) and 12 C(p,n) reactions cross sections reasonably reproduce available experimental data for neutron source consisting of the thin lithium foil and thick carbon beam stopper Preliminary analysis of Bi(n,xn) activation cross sections σ: - σ at specific neutron energy En can be deduced from measurements when the incident neutron energy is below the energy of σ maximium - otherwise C/E ratio serves as validation criterion of σ(e) in the energy range from threshold to incident energy En March 2009, Prague Workshop on Activation Data EAF

Simulation of quasi-monoenergetic Li(p,n) neutron source up to 50 MeV proton energy

Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Nuclear Physics Institute Řež Simulation of quasi-monoenergetic Li(p,n) neutron source up to 50 MeV proton energy S.P. Simakov 1, P. Bém 2, V.