Title: ANITA neutron source
1ANITA neutron source
- Monte Carlo simulations and comparison with
experimental data
Mitja Majerle Nuclear Physics Institute Rež near
Prague
2Outline
- Summary of experimental data from June 08
- Simulations - FLUKA
- Geometry
- General properties, neutron fluences,
- EXP/SIM protons
- Simulations MCNPX
- Conclusion
3Experimental 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
user1 cross of detectors Cu detector
user2, user3 positions (6m, 12m)
collimator
concrete wall
for LE neutrons
4Monte 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
5Simulated 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
6XZ around target
Neutron flux in XZ
Proton flux in XZ
FLUKA simulations
7XY before collimator
Proton flux in XY
Neutron flux in XY
Protons at 1T magnetic field
FLUKA simulations
8XY after collimator
Neutron flux in XY
Proton flux in XY
FLUKA simulations
9Spectral fluences
- 31010 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
kuser1/user0 to get better statistics
FLUKA simulations
10Activation 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
11Experiment / calculation
FLUKA simulations
12Protons 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)
13MCNPX
- 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
- 5108 histories, slower simulations
142D distributions
Neutrons and protons in XZ around the target
Neutrons in XY before and after iron wall
MCNPX simulations
15Neutron 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
16EXP/SIM for MCNPX
MCNPX simulation, BERTINI/DRESNER Average EXP/SIM
1.5
MCNPX simulation, CEM Average EXP/SIM 1.6
17Conclusion
- 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.
18XY before collimator at 1T magnetic field
Neutron flux in XY
Proton flux in XY
FLUKA simulations
1925 keV peak
56Fe(n,TOT) cross sections from ENDF