Transcript Diapositiva 1

THE RADIATION FIELDS AROUND A PROTON
THERAPY FACILITY: A COMPARISON OF MONTE
CARLO SIMULATIONS
Dr. Sandro Sandri
(President of Italian Association of Radiation Protection, AIRP)
Head, Radiation Protection Laboratory, IRP FUAC Frascati
ENEA – Radiation Protection Istitute
[email protected]
12th International Symposium on
Radiation Physics
07 to 12 October 2012 - Rio de Janeiro - RJ
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CONTENTS
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The TOP-IMPLART
Scope of the analysis
Simulation model
The computer codes
Results
Discussion and conclusion
S. Sandri - 12th International Symposium on Radiation Physics - Rio de Janeiro - RJ
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TOP-IMPLART accelerator
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TOP-IMPLART are the acronym of Terapia Oncologica con Protoni (Oncological
Therapy with Protons) and Intensity Modulated Proton Linear Accelerator for
Therapy
The first 7 MeV module of the accelerator, is already installed and has been tested
Additional modules will be added leading proton energy to 30, 70 and 150 MeV
In the final layout the bunker will be 30 m long and 3 m wide
S. Sandri - 12th International Symposium on Radiation Physics - Rio de Janeiro - RJ
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COMPUTER CODES
• The principal subject of the current work is the
analysis of the performance of two different
computer codes
• both based on the Monte Carlo algorithm:
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FLUKA (FLUktuierende KAskade) and
MCNPX (Monte Carlo N-Particle eXtended)
• Info on the web sites:
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www.fluka.org
mcnpx.lanl.gov
S. Sandri - 12th International Symposium on Radiation Physics - Rio de Janeiro - RJ
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SIMULATION MODEL
• The model has been developed to simulate a 150 MeV
proton beam
• hitting a water phantom of cubic form, 32 cm thick
(32x32x32 cm3)
• with 2 mm plexiglass walls
• and located in front to the kapton membrane, 50 µm
thick, that seals the vacuum chamber of the accelerator
• Between the kapton membrane and the phantom there is
a 2 cm air gap
• The cross section of the proton beam reaching the kapton
membrane has the maximum dimension of 7 mm (in x
and y directions)
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SECONDARY PARTICLES
Several secondaries are generated in the inelastic interactions
of the beam protons with the target components (plexiglass and water).
Both the codes were able to follow the different produced particles
and provided different kind of related results.
FLUKA for examples provided the following table per beam particle
SECONDARIES
4-HELIUM
3-HELIUM
TRITON
DEUTERON
PROTON
ELECTRON
POSITRON
NEUTRIE
ANEUTRIE
PHOTON
NEUTRON
FLUKA RESULTS
PROMPT RADIATION
1.3456E-01 (23.0%)
6.2313E-03 (1.1%)
3.2014E-03 (0.5%)
1.1862E-02 ( 2.0%)
2.4968E-01 (42.8%)
7.0562E-02 (12.1%)
1.0773E-01 (18.5%)
TOTAL
5.8383E-01 (100.%)
S. Sandri - 12th International Symposium on Radiation Physics - Rio de Janeiro - RJ
RADIOACTIVE DECAYS
9.9215E-04 ( 0.9%)
6.6010E-03 ( 5.8%)
4.8514E-02 (42.8%)
4.8514E-02 (42.8%)
6.5313E-03 ( 5.8%)
2.1726E-03 ( 1.9%)
1.1332E-01 (100.%)
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NEUTRON PRODUCTION
The comparison of the data for neutron production
shows a reasonable agreement between the two codes.
However using the libraries in MCNPX the neutron yield is about 7% higher
FLUKA NEUTRONS PER PROTON
1.0773E-01
2,6%
MCNPX METHOD
MCNPX NEUTRONS PER PROTON
Bertini model
1.0485E-01
La150h 150 MeV Los Alamos proton Library
1.1192E-01
ENDF70prot 150 MeV ENDF proton Library
1.1239E-01
S. Sandri - 12th International Symposium on Radiation Physics - Rio de Janeiro - RJ
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PARAMETERS OF COMPARISON
the comparison of the code concentrated on the
following fluence results:
• Proton fluence in the target and in air around the
target
• Neutron fluence in the target and in air around the
target
• Photon fluence in the target and in air around the
target
S. Sandri - 12th International Symposium on Radiation Physics - Rio de Janeiro - RJ
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FLUKA proton fluence
• In FLUKA the spatial distribution of a quantity can be
reported in a 2d chromatic picture
• MCNPX doesn’t have this capability
Water phantom
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MCNPX proton fluence
• MCNPX, Proton fluence in air, 100 cm after the target
• The total proton flux of about 1 10-8 (8,44%
uncertainty) is the same of FLUKA
0 deg Tot flux=9.80963E-09 ± 8.44%
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Flux (Proton cm GeV proton beam )
1E-6
-2
1E-7
1E-8
0.00
0.02
0.04
0.06
0.08
0.10
Energy (GeV)
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Photon fluence
FLUKA
MCNPX
0.01
1E-4
1E-5
1E-6
-2
-1
Flux ( cm GeV proton)
1E-3
1E-7
1E-8
0 deg
30 deg
60 deg
90 deg
120 deg
150 deg
180 deg
1E-9
1E-10
1E-11
1E-5
1E-4
1E-3
0.01
0.1
Energy (GeV)
Discrepancies in the results for photons are mainly due to different units and scaling
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Neutron fluence
FLUKA
MCNPX
10000
1000
0 deg
30 deg
60 deg
90 deg
120 deg
150 deg
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1
0.1
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-1
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Flux (n cm GeV proton )
100
0.01
1E-3
1E-4
1E-5
1E-6
1E-7
1E-8
1E-9
1E-10
1E-11
1E-11 1E-10 1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
0.01
0.1
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Energy (GeV)
Due to the different units, the qualitative path only can be compared in the graphs,
showing a good agreement
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FLUKA, Neutron fluence, spatial distribution
Neutrons are more intense in the forward direction, as foreseeable
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CONCLUSIONS
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Both computer codes used in the simulation are well suitable to be
applied to the analysis of the secondary radiation produced by the
proton beam of the TOP-IMPLART accelerator
While MCNPX seems to be more flexible in the data library selection
and update, FLUKA can provide a more complete output in term of
graphical detail
Another advantage of MCNPX is the availability of versions developed
to run on the world wide diffused Windows™ personal computer, on
the other hand FLUKA can be installed on a pc with Linux system
The results obtained with the two codes showed a good agreement for
the fluence vs energy spectra of the neutrons (the main secondary
radiation)
In conclusion both the codes are appropriate for the specific calculation
and the selection should be mainly based on the hardware and
operative system availability, and on the specific skilfulness of the users
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