Dr. Sandro Sandri ( President of Italian Association of Radiation Protection , AIRP)

1

Dr. Sandro Sandri(President of Italian Association of Radiation Protection, AIRP)Head, Radiation Protection Laboratory, IRP FUAC FrascatiENEA – Radiation Protection Istitute [email protected] 12th International Symposium on Radiation Physics

07 to 12 October 2012 - Rio de Janeiro - RJ

THE RADIATION FIELDS AROUND A PROTON THERAPY FACILITY: A COMPARISON OF MONTE CARLO SIMULATIONS

CONTENTS

S. Sandri - 12th International Symposium on Radiation Physics - Rio de Janeiro - RJ 2

• The TOP-IMPLART• Scope of the analysis• Simulation model• The computer codes• Results• Discussion and conclusion

TOP-IMPLART accelerator

• 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

3S. Sandri - 12th International Symposium on Radiation Physics - Rio de Janeiro - RJ

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:• FLUKA (FLUktuierende KAskade) and• MCNPX (Monte Carlo N-Particle eXtended)

• Info on the web sites:• www.fluka.org• mcnpx.lanl.gov


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)


SECONDARY PARTICLES

SECONDARIES FLUKA RESULTS

PROMPT RADIATION RADIOACTIVE DECAYS4-HELIUM 1.3456E-01 (23.0%) 9.9215E-04 ( 0.9%)3-HELIUM 6.2313E-03 (1.1%)

TRITON 3.2014E-03 (0.5%) DEUTERON 1.1862E-02 ( 2.0%)

PROTON 2.4968E-01 (42.8%) ELECTRON 6.6010E-03 ( 5.8%)POSITRON 4.8514E-02 (42.8%)NEUTRIE 4.8514E-02 (42.8%)

ANEUTRIE 6.5313E-03 ( 5.8%)PHOTON 7.0562E-02 (12.1%) 2.1726E-03 ( 1.9%)

NEUTRON 1.0773E-01 (18.5%)

TOTAL 5.8383E-01 (100.%) 1.1332E-01 (100.%)


Several secondaries are generated in the inelastic interactionsof the beam protons with the target components (plexiglass and water).

Both the codes were able to follow the different produced particlesand provided different kind of related results.

FLUKA for examples provided the following table per beam particle

NEUTRON PRODUCTION


The comparison of the data for neutron productionshows a reasonable agreement between the two codes.

However using the libraries in MCNPX the neutron yield is about 7% higher

MCNPX METHOD MCNPX NEUTRONS PER PROTONBertini model 1.0485E-01

La150h 150 MeV Los Alamos proton Library 1.1192E-01ENDF70prot 150 MeV ENDF proton Library 1.1239E-01

FLUKA NEUTRONS PER PROTON

1.0773E-01 2,6%

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


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

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


0.00 0.02 0.04 0.06 0.08 0.101E-8

1E-7

1E-6

Flux

(Pro

ton

cm-2 G

eV-1pr

oton

bea

m-1)

Energy (GeV)

0 deg Tot flux=9.80963E-09 ± 8.44%

Photon fluence

FLUKA MCNPX


1E-5 1E-4 1E-3 0.01 0.11E-11

1E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

Flux

( c

m-2 G

eV-1 p

roto

n)Energy (GeV)

0 deg 30 deg 60 deg 90 deg 120 deg 150 deg 180 deg

Discrepancies in the results for photons are mainly due to different units and scaling

Neutron fluence

FLUKA

MCNPX

1E-11 1E-10 1E-9 1E-8 1E-7 1E-6 1E-5 1E-4 1E-3 0.01 0.1 11E-11

1E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

1

10

100

1000

10000

Flux

(n c

m-2

GeV

-1 p

roto

n-1)

Energy (GeV)

0 deg 30 deg 60 deg 90 deg 120 deg 150 deg


Due to the different units, the qualitative path only can be compared in the graphs,showing a good agreement

FLUKA, Neutron fluence, spatial distribution

Neutrons are more intense in the forward direction, as foreseeableS. Sandri - 12th International Symposium on Radiation Physics - Rio de Janeiro - RJ 13

CONCLUSIONS

• 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


Dr. Sandro Sandri ( President of Italian Association of Radiation Protection , AIRP)

Documents

Transcript of Dr. Sandro Sandri ( President of Italian Association of Radiation Protection , AIRP)