Transcript The SPES production target - LNL-INFN

The SPES production target
first calculations using the FLUKA code
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Abstract
Monte Carlo simulations play a very important role in the
prediction of the physical behavior during any kind of
process, and irradiation as well. It can be helpful for the
equivalent dose absorption rate or for the product
spectra predictions, and is constantly improved with the
rising calculation performances in modern computers. In
this report we are going to introduce the aim of the SPES
facility, and then we will focus on the FLUKA Monte Carlo
code, a powerful tool that allows simulating the physical
processes with the SPES beam and geometry. We will
show that the results are close to the ones achieved with
the MCMPX code, an improved software previously used
by the SPES team.
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INTRODUCTION
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What’s FLUKA?
• General Monte Carlo tool for calculations of
particle transport and interaction with matter;
• Distributed and documented on the official
website http://www.fluka.org;
• Developed and maintained under INFN and
CERN agreement;
• Has a wide range of applications.
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FLUKA’s applications
• Cosmic ray's physic;
• Accelerator design (LHC systems);
• Particle physics: calorimetry, tracking and
detector simulations etc. (ALICE, ICARUS);
• Neutrino physics (CNGS);
• Shielding design;
• Dosimetry and radioprotection;
• Space radiation (space related studies partially
funded by NASA);
• Hadron therapy (treatment planning).
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FLUKA collaborations
•
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CERN (Switzerland): M. Brugger, F. Cerutti, A. Ferrari, M. Mauri, G. Lukasik, S.
Roesler, L. Sarchiapone, G. Smirnov, F. Sommerer, C. Theis, S. Trovati, H. Vinke, V.
Vlachoudis
SLAC (USA): A. Fassò
Univ. of Siegen (Germany): J. Ranft
INFN & Univ. Milano (Italy): G. Battistoni, F. Broggi, M. Campanella, P. Colleoni, E.
Gadioli, S. Muraro, P.R. Sala
INFN Frascati: M. Carboni, C. D’Ambrosio, A. Ferrari, A. Mostacci, V. Patera, M.
Pelliccioni, R. Villari
Univ. Roma II (Italy): M.C. Morone
INFN & Univ. Bologna (Italy): A. Margiotta, M. Sioli
DKFZ & HIT (Heidelberg, Germany): A. Mairani, K. Parodi
Univ. of Houston (USA): A. Empl, L. Pinsky
NASA-Houston (USA): K.T. Lee, T. Wilson, N. Zapp
ARC Seibersdorf (Austria): S. Rollet
Chalmers Univ. of Technology (Sweden): M. Lantz
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FLUKA’s abilities
• Handles 60 different particles and Heavy Ions;
• Hadron-hadron and hadron-nucleus interactions up to
10000 TeV;
• Electromagnetic and μ interactions 1 keV - 10000 TeV;
• Nucleus-nucleus interactions 100 MeV/n to 10000 TeV/n;
• Charged particle transport – ionization energy loss;
• Neutron multi-group transport and interactions 0-19.6
MeV;
• Neutrino interactions;
• Transport in magnetic field;
• Combinatorial and Voxel geometry (“3D pixel”);
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Flair graphic interface
• Advanced user interface for
FLUKA by Vlachoudis et al.,
written in Python and Tkinter;
• Facilitates the editing of the input
file, and the data merging;
• Downloadable from FLUKA
website, but not part of FLUKA;
• Extremely useful for geometry
view and debug;
• Uses Gnuplot to generate
graphics;
• Gives the possibility of running
processes in more cores (with
different seeds);
• Runs under Linux
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Different kind of plots
Povray
Gnuplot
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SimpleGeo
• interactive solid modeler
which allows for flexible
and easy creation of the
geometry models via drag
& drop, as well as on-thefly inspection
• Imports existing
geometries for viewing
• Creating new geometries
from scratch
• Export to various formats
(FLUKA, MCNP,MCNPX)
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Target – ion source SPES
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FLUKA for SPES experiment
• Benchmarking of the
code, results compared
with a previously used
program (MCMPX);
• 40 MeV proton beam
with a 200 µA current
hitting a target made of
graphite and UC4;
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PHYSICS
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Low energy neutrons in FLUKA
• Many particle are subject to point-wise dynamic;
• Neutrons below 20 MeV (19.6 MeV for the old
library) are subject to multigroup algorithm
– Very used in low-energy transport codes;
– Based on the division of energy spectrum in a discrete
number of energy groups;
– This range is continuously enriched and updated on
the basis of many recent evaluations;
– Elastic and inelastic scattering simulated by group-togroup transfer probabilities (down-scattering matrix);
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Multigroup algorithm logic
 a11  a1n 


    
a  a 
nn 
 n1
In a material a certain kind of scattering probability between
two groups is proportional to the matrix element aij, where i
and j are the group indexes.
Downscattering matrix
2i +1
Pi (m )s si (g ® g')
i=0 4p
N
s s ( g ® g', m ) = å
σ: cross section
µ: scattering angle
N: chosen order of Legandre anisotropy
P: Legandre polynomial function
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Cross section library
• Available at many temperature for different
materials (0, 87, 273 K);
• Hydrogen cross section available for three
kind of binding:
– Free
– H2O
– CH2
• Also photon scattering is treated with a
multigroup scheme.
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Library improvements
Old library
New library
Up to 19.6 MeV
Up to 20.0 MeV
72 neutron groups, 1 thermal
260 neutron groups, 31 thermal
22 gamma groups
42 gamma groups
140 different materials/isotopes
About 200 materials/isotopes at 0, 87 K
and 296 K
Self-shielding for Fe, Cu, Pb
Self shielding for most isotopes
Moreover, the point-wise library has been extended from few isotopes
(H, 6Li, 10B, Ar, Xe and Cd) to all.
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Residual nuclei scoring
• For many materials group-dependent
information on the residual nuclei produced
by low-energy neutron interactions isavailable
in FLUKA library.
• This information can be used to score the
residual nuclei after any fission/spallation
reaction, and this feature has been useful for
the work shown in this report for the UC4
fission production.
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RESULTS
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Power deposition
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Power deposition
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Power deposition
• Not centered beam
(1cm from the center);
• Gaussian beam
(σ=2.7mm);
• Good results, possible
different developments.
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Nuclear production from the target
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Bertini + Orn production plot
Produzione al tempo 0
x 10
11
2
N protons
80
1.5
60
1
40
0.5
20
0
0
50
100
150
0
N neutrons
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Bertini + Ral production plot
Produzione al tempo 0
10
x 10
8
90
7
80
70
6
N protons
60
5
50
4
40
3
30
2
20
1
10
0
0
50
100
150
0
N neutrons
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Comparison with MCMPX
Nuclei production spectrum as a function of the nuclear mass
1E+14
1E+13
Production rate [nuc./cm³s]
1E+12
1E+11
FLUKA
1E+10
BerOrn
1E+09
BerRal
1E+08
1E+07
1E+06
0
50
100
150
200
250
Nuclear mass
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Comparison with MCMPX
Sn production spectrum
1E+12
Production rate [nuc./cm³s]
1E+11
1E+10
FLUKA
1E+09
BerOrnl
BerRal
1E+08
1E+07
1E+06
100
105
110
115
120
125
130
135
140
145
150
Nuclear mass
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Comparison with MCMPX
Cs production spectrum
1E+12
Production rate [nuc./cm³s]
1E+11
1E+10
FLUKA
1E+09
BerOrn
BerRal
1E+08
1E+07
1E+06
120
125
130
135
140
145
150
155
160
Nuclear mass
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Neutron yield
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Dose and activity scoring
•
•
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•
•
Important for radioprotection part;
Decays may be activated in FLUKA,
and the equivalent dose may be
recorded at different times;
It’s possible to make a map of the
bunker with the target and the
equivalent dose rate in each region;
Dose sampled at 1 and 2 meters from
the target at different irradiation and
cooling times;
3 phases:
– Irradiation (14 days);
– Cooling (14 days);
– Storage.
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Dose and activity scoring
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Results in Fluka
Irradiation
Step
Activity [Bq]
Dose at 1m
Dose at 2m
1 day
3.53E+13
2.08E+00
6.11E-01
4 days
3.85E+13
2.18E+00
6.40E-01
7 days
3.97E+13
2.21E+00
6.49E-01
14 days
4.09E+13
2.25E+00
6.60E-01
Cooling
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Step
Activity [Bq]
Dose at 1m
Dose at 2m
1 second
3.87E+13
2.08E+00
6.16E-01
1 day
5.66E+12
1.71E-01
5.02E-02
3 days
3.23E+12
9.64E-02
2.84E-02
14 days
1.01E+12
3.50E-02
1.04E-02
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Results in MCMPX
Irradiation
Step
Activity [Bq]
Dose at 1m
Dose at 2m
1 day
1.50E+13
1.77E+00
4.43E-01
4 days
1.70E+13
1.92E+00
4.79E-01
7 days
1.80E+13
1.94E+00
4.86E-01
14 days
2.00E+13
2.09E+00
5.22E-01
Step
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NotCooling
too good, but the fission rate (9.23E12 fissions/sec)
to theatMCMPX
one (8E12
Activity [Bq] is close Dose
1m
Dosefissions/sec)
at 2m
1 second
2.00E+13
2.08E+00
5.19E-01
1 day
3.33E+12
1.95E-01
4.88E-02
3 days
1.78E+12
1.10E-01
2.75E-02
14 days
6.67E+11
4.12E-02
1.03E-02
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Dose scoring inside the box
• After the 14 days of
cooling the target is put
into a lead and iron box;
• Is not possible to
change the geometry
during the virtual time
of the simulation;
• Different strategy has to
be adopted in order to
prevent the activation
of the box.
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Geometry of the after-cooling
simulation
Box
Low-energy neutron proof layer
Air
Target
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Results
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Results
Time elapsed
Dose at 1 m [Sv/h]
Dose at 2 m
Dose at 2m
(MCMPX)
30 days
9,41∙10-4
3,85∙10-4
2,75∙10-4
90 days
1,57∙10-4
6,42∙10-5
5,98∙10-5
10 years
2,67∙10-7
9,78∙10-8
4,25∙10-7
100 years
2,56∙10-8
8,65∙10-9
7,24∙10-8
Problems due to:
• Geometry of the sampling;
• Low statistics (50 000 events)
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Boris tube
• Important in order to
transmit data from the
chamber to the outside;
• External width: 330 mm
• Iron width: 10 mm
• PEHD diameter: 315
mm
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Boris tube
• Positive results, no
detectable scoring
outside the chamber
through the tubes;
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Neither any neutron outside
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Conclusions
• Strong points:
– User friendly program;
– Many application in physics;
– Results benchmarked in:
•
•
•
•
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Dose scoring;
Nuclear production;
Fission rate;
Power deposition
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Conclusions
• Weak points:
– Overrated activity;
– Tricky when the geometry of the problem has to
change;
• Further developments:
– Benchmark with GEANT4;
– Improved experiment with the box, and with other
methods to “record” the activity of the target after 14
days of radiation;
– FLUKA on GRID;
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Thanks
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Appendix
SOME EXAMPLES OF PROGRAM
USAGE
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Installing FLUKA
• Decompress the main folder;
• Make sure to have a FORTRAN compiler;
• Set the environment variable FLUPRO (path of the
folder) and FLUFOR (name of the compiler);
• Run the makefile inside the folder;
• Create a startup bash script to include the FLUKA
directory in the program path of Bash;
• Every detail is in the readme file;
• Flair is even easier, DEB packages.
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Example of a run
rfluka –N0 –M1 exp1
Input file (no extension)
Calls the script
Previous and last cycle of the simulation
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Example of an input file
* ..+....1....+....2....+....3....+....4....+....5....+....6....+....7...
TITLE
FLUKA Course Exercise
*
DEFAULTS
NEW-DEFA
*
* beam definition
BEAM
-3.5
-0.8
-1.7
PROTON
BEAMPOS
-0.1
*
* Geometry
* -------* use names everywhere and free format for geometry (conventional format)
GEOBEGIN
COMBNAME
0 0
Cylindrical Target
*
* Bodies
* -----*
* Blackhole to include geometry
SPH BLK 0.0 0.0 0.0 10000.0
* Void sphere
SPH VOID 0.0 0.0 0.0 1000.0
* Cylindrical target:
RCC TARG 0.0 0.0 0.0 0.0 0.0 10. 5.
*
END
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*
* Regions
* ------*
* Blackhole
BLKHOLE
5 +BLK -VOID
* Void
VOID
5 +VOID -TARG
* Target
TARGET
5 +TARG
*
END
GEOEND
*
* Assign materials
* ---------------ASSIGNMA BLCKHOLE BLKHOLE
ASSIGNMA
VACUUM
VOID
ASSIGNMA
LEAD TARGET
*
RANDOMIZ
1.0
START
10.0
STOP
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0
Flair first screenshot
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Input with Flair
All the cards organized per category
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