Compact, Energy Self-Sustaining Neutron Source: Enabling ...
ANITA neutron source
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Transcript of ANITA neutron source
ANITA workshop, Uppsala, december 2008
ANITA neutron source
Monte Carlo simulations and comparison with experimental data
Mitja Majerle
Nuclear Physics Institute
Řež near Prague
ANITA workshop, Uppsala, december 2008
Outline
Summary of experimental data from June ‘08 Simulations - FLUKA:
Geometry General properties, neutron fluences, EXP/SIM protons
Simulations – MCNPX Conclusion
ANITA workshop, Uppsala, december 2008
Experimental data Activation detectors
at user1-user3 Data presented at
EFNUDAT meeting: Uniform beam LE neutrons from
background Protons not
detected Detectable limit for
neutrons reached at user2 and user3
user2, user3 positions
(6m, 12m)
concrete wall
collimator
user1
cross of detectors +
Cu detector
for LE neutrons
ANITA workshop, Uppsala, december 2008
Monte Carlo simulations
FLUKA PEANUT spallation model ENDF library up to 20 MeV
MCNPX Bertini/Dresner, CEM, INCL/ABLA spallation models LA150, NRG2003, TENDL libraries up to 150 MeV
Setup description from schematic drawings (beam at 3 deg right, y=-3mm), magnetic field 0.15 T
ANITA workshop, Uppsala, december 2008
Simulated quantities
Neutron and proton flux in 3 planar cross-sections: XZ around target XY before collimator XY behind collimator
Neutron and proton spectral fluences: 10x10 cm2 before
collimator – “user0” 2x2 cm2 in user1-user3
ANITA workshop, Uppsala, december 2008
XZ around target
FLUKA simulations
Neutron flux in XZ Proton flux in XZ
ANITA workshop, Uppsala, december 2008
XY before collimator
FLUKA simulations
Protons at 1T magnetic field
Neutron flux in XY
Proton flux in XY
ANITA workshop, Uppsala, december 2008
XY after collimator
FLUKA simulations
Neutron flux in XY Proton flux in XY
ANITA workshop, Uppsala, december 2008
Spectral fluences
3*1010 histories Detector 2x2 cm2 positioned
250 cm from the target – user1 Neutrons:
100 log bins (4 keV..20 MeV) 160 bins (20..180 MeV)
Protons: 180 bins (0..180 MeV)
Proton spectrum sampled at user0 multiplied with k=user1/user0 to get better statistics
FLUKA simulations
user1
1E-11
1E-9
1E-7
1E-5
1E-3
1E-1
1E-6 1E-5 1E-4 1E-3 1E-2 1E-1 1E+0
Energy [GeV]
flu
ence
[G
eV-1
cm
-2 p
roto
n-1
]
neutrons
protons
protons user0/user1
user1*E
1E-9
1E-8
1E-7
1E-6
1E-5
1E-6 1E-5 1E-4 1E-3 1E-2 1E-1 1E+0
Energy [GeV]
flu
ence
*E [
cm-2
pro
ton
-1]
ANITA workshop, Uppsala, december 2008
Activation detectors
Neutron spectral fluence is folded with cross sections (TALYS 1.0 + correction to better fit EXFOR data)
Isotopes: 7xAu 2xAl 6xBi 5xTa 3xCu
Uncertainties: 10-15% spectroscopy ~2% statistical (simulation) ~ 10% and more TALYS cross
sections
(n,xn) cross-sections in Au
0
0.5
1
1.5
2
2.5
1E-6 1E-5 1E-4 1E-3 1E-2 1E-1 1E+0
Energy [MeV]
Cro
ss
se
cti
on
[b
arn
s]
n,2n
n,4n
n,6n
n,8n
user1
1E-11
1E-9
1E-7
1E-5
1E-3
1E-1
1E-6 1E-5 1E-4 1E-3 1E-2 1E-1 1E+0
Energy [GeV]
flu
ence
[G
eV-1
cm
-2 p
roto
n-1
]
neutrons
protons
protons user0/user1
ANITA workshop, Uppsala, december 2008
Protons in the beam Proton background in simulation
is suppressed for a factor of 1300 1300=(number of
neutrons/number of protons) in energy range 1-200 MeV
This is 40x lower than the detection limit of used activation detectors – 63Cu(p,n)63Zn 40=(the smallest mass of Zn that
could be detected with 98% accuracy)/(simulated mass of Zn)
Only from experiment we can say that protons are suppressed at least for a factor of 30 (with 98% probability, vs. neutrons)
user1
1E-11
1E-9
1E-7
1E-5
1E-3
1E-1
1E-6 1E-5 1E-4 1E-3 1E-2 1E-1 1E+0
Energy [GeV]
fluen
ce [G
eV-1
cm
-2 p
roto
n-1
]
neutronsprotonsprotons user0/user1
ANITA workshop, Uppsala, december 2008
MCNPX The same geometry and materials as in FLUKA was
implemented in MCNPX MCNPX has no possibility to simulate magnetic field
(which has negligible influence anyway) 3 cascade models were tested:
Bertini CEM INCL/ABLA
5*108 histories, slower simulations
ANITA workshop, Uppsala, december 2008
2D distributions
MCNPX simulations
Neutrons and protons in XZ around the target
Neutrons in XY before and after iron wall
ANITA workshop, Uppsala, december 2008
Neutron spectral fluences
Spectra calculated with MCNPX are similar to FLUKA spectra at first look
Differences in 20-150 MeV region are up to 50%, MCNPX is systematically lower (libs, geometry?)
Can experiment determine the best spectrum ? Activation detectors
themselves have ca. 50% spread
User0
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E-6 1E-5 1E-4 1E-3 1E-2 1E-1 1E+0
Energy [GeV]
Neu
tron
flue
nce
[GeV
-1 c
m-2
prot
on-1
]FLUKA
MCNPX INCL/ABLA
MCNPX CEM
MCNPX BERTINI/DRESNER
ANITA workshop, Uppsala, december 2008
EXP/SIM for MCNPX
0
0.5
1
1.5
2
2.5
3
MCNPX simulation, BERTINI/DRESNER
Average EXP/SIM ~ 1.5
0
0.5
1
1.5
2
2.5
3
MCNPX simulation, CEM
Average EXP/SIM ~ 1.6
ANITA workshop, Uppsala, december 2008
Conclusion
Accurate simulations confirmed our experimental conclusions: uniform beam, no protons.
EXP/SIM for activation detectors is ca. 1, with the spread ca. 50%.
Spectra calculated with different models differ for 50%.
All presented data are available at:http://ojs.ujf.cas.cz/~mitja/download/uppsala
The access to the METACentrum computing facilities provided under the research intent MSM6383917201 is appreciated.
ANITA workshop, Uppsala, december 2008
XY before collimator at 1T magnetic field
FLUKA simulations
Neutron flux in XY Proton flux in XY