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REMSIM Geant4 Simulation

REMSIM Geant4 Simulation. S. Guatelli 1 , B. Mascialino 1 , P. Nieminen 2 , M. G. Pia 1 INFN Sezione di Genova ESA - ESTEC. 4th Workshop on Geant4 Bio-medical Developments and Geant4 Physics Validation 14 th July 2005, Genova, Italy. www.ge.infn.it/geant4/space/remsim. Context.

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REMSIM Geant4 Simulation

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  1. REMSIM Geant4 Simulation • S. Guatelli1, B. Mascialino1, P. Nieminen2, M. G. Pia1 • INFN Sezione di Genova • ESA - ESTEC 4th Workshop on Geant4 Bio-medical Developments and Geant4 Physics Validation 14th July 2005, Genova, Italy www.ge.infn.it/geant4/space/remsim

  2. Context • Planetary exploration has grown into a major player in the vision of space science organizations like ESA and NASA • The study of the effects of space radiation on astronauts is an important concern of missions for the human exploration of the solar system • The radiation hazard can be limited: • selecting traveling periods and trajectories • providing adequate shielding in the transport vehicles and surface habitats

  3. Scope of the REMSIM Geant4 application The project takes place in the framework of the AURORA programme of the European Space Agency Quantitative evaluation of the physical effects of space radiation in interplanetary manned missions Scope Vision A firstquantitative analysis of the shielding properties of some innovative conceptual designs of vehicle and surface habitats Comparison among different shielding options

  4. Summary of process products See http://www.ge.infn.it/geant4/space/remsim/environment/artifacts.html

  5. REMSIM Simulation Design

  6. Vehicle concepts Surface habitats Astronaut Electromagnetic processes + Hadronic processes Strategy of the Simulation Study • Model the radiation spectrum according to current standards • simplified angular distribution to produce statistically meaningful results • Physics modeled by Geant4 • Select appropriate models from the Toolkit • Verify the accuracy of the physics models • Distinguish e.m. and hadronic contributions to the dose • Simplified geometrical configurations • retaining the essential characteristics for dosimetry studies • Evaluate energy deposit/dose in shielding configurations • various shielding materials and thicknesses

  7. Space radiation environment • Galactic Cosmic Rays • Protons, α particles and heavy ions (C -12, O -16, Si - 28, Fe - 52) • Solar Particle Events • Protons and α particles 100K primary particles, for each particle type Energy spectrum as in GCR/SPE Scaled according to fluxes for dose calculation GCR: p, α, heavy ions SPE particles: p and α at 1 AU at 1 AU Envelope of CREME96 1977 and CREME86 1975 solar minimum spectra Envelope of CREME96 October 1989 and August 1972 spectra Worst case assumption for a conservative evaluation

  8. SIH - Simplified Inflatable Habitat Vehicle concepts Two (simplified) options of vehicles studied Simplified Rigid Habitat A layer of Al (thickness suggested by Alenia) Modeled as a multilayer structure consisting of: • MLI: external thermal protection blanket - Betacloth and Mylar • Meteoroid and debris protection - Nextel (bullet proof material) and open cell foam • Structural layer - Kevlar • Rebundant bladder - Polyethylene, polyacrylate, EVOH, kevlar, nomex Materials and thicknesses by ALENIA SPAZIO The Geant4 geometry model retains the essential characteristics of the vehicle concept relevant for a dosimetry study

  9. Sketch and sizes by ALENIA SPAZIO Surface Habitats • Example: surface habitat on the moon • Cavity in the moon soil + covering heap The Geant4 model retains the essential characteristics of the surface habitat concept relevant to a dosimetric study

  10. 30 cm Z Astronaut Phantom • The Astronaut is approximated as a phantom • a water box, sliced into voxels along the axis perpendicular to the incident particles • the transversal size of the phantom is optimized to contain the shower generated by the interacting particles • the longitudinal size of the phantom is a “realistic” human body thickness • The phantom is the volume where the energy deposit is collected • The energy deposit is given by the primary particles and all the secondaries created

  11. Selection of Geant4 Physics Models • E. M. physics: • Geant4 Low Energy Package for p, α, ions and their secondaries • Geant4 Standard Package for positrons • Hadronic physics: • Elastic scattering • Inelastic Scattering • Protons, neutrons, pions: two alternative approaches (next slide) • Alpha: LEP model ( up to 100 MeV), Binary Ion model (80 MeV- 100 GeV/nucl), Tripathi and Shen cross sections active • Neutron fission and capture active

  12. Selection of Geant4 Hadronic Physics Models Hadronic Physics for protons and α as primary particles + hadronic elastic process

  13. vacuum air GCR particles shielding phantom multilayer - SIH Study of vehicle concepts SIH • Incident spectrum of GCR particles • Energy deposit in phantom due to electromagnetic interactions • Add the hadronic physics contribution to the energy deposit on top Geant4 model Configurations • SIH only, no shielding • SIH + 10 cm water / polyethylene shielding • SIH + 5 cm water / polyethylene shielding • 2.15 cm aluminum structure • 4 cm aluminum structure The results are obtained with simulations of 100 K events

  14. Generating primary particles: strategy SIH + 10 cm water GCR p • First step: • Generate GCR particles with the entire input energy spectrum • Second step: • Generate GCR p and α with defined slices of the energy spectrum: • 130 MeV/nucl < E < 700 MeV/nucl • 700 MeV/nucl < E < 5 GeV/nucl • 5 GeV/nucl < E < 30 GeV/nucl • E > 30 GeV/nucl • Study the energy deposit in the phantom with respect to the slice of the energy spectrum of the primaries GCR p with 5 GeV < E < 30 GeV

  15. Analysis of the results • The Kolmogorov-Smirnov test was used to compare the energy deposit in the phantom, in different shielding configuration, to point out equivalent shielding behaviors • The test calculates the probability (p-value) that two distributions derive from the same quantity • p-value > 0.05 points out an equivalent shielding behavior

  16. water phantom GCR p SIH + 10 cm water Simulation results – GCR p Energy deposit with respect to the depth in the phantom • The Kolmogorov-Smirnov test shows that the effect of the Bertini and Binary sets do not differ significantly in the calculation of the energy deposited (p-value = 0.11); • Adding the hadronic interactions on top of the electromagnetic processes increases the energy deposited in the phantom of ~27%. Z E.M. physics E.M. + hadronic physics – binary set E.M. + hadronic physics – bertini set

  17. Z water phantom GCR α SIH + 10 cm water Simulation results – GCR α Energy deposit with respect to the depth in the phantom • The contribution of the hadronic interactions with respect to the electromagneticone is statistically negligible ( Kolmogorov-Smirnov test result: p-value = 0.95) E.M. physics E.M. + hadronic physics

  18. Z water phantom GCR α SIH + 10 cm water Simulation results SIH + 10 cm water shielding • GCR p • Energy deposit given by both e.m. and hadronic interactions in the phantom 130 MeV – 700 MeV 700 MeV – 5 GeV 5 GeV – 30 GeV E > 30 GeV

  19. Simulation results SIH + 10 cm water shielding • Total energy deposit in the phantom, given by every slice of the GCR p energy spectrum • The biggest contribution derives from the intermediate energy range: 700 MeV < E < 30 GeV GCR p

  20. Z water phantom GCR α SIH + 10 cm water Simulation results SIH + 10 cm water shielding • GCR α • Energy deposit given by both e.m. and hadronic interactions in the phantom • The energy deposit is not weighted with the probability of the specific energy spectrum slice 130 MeV/nucl < E < 700 MeV/nucl 700 MeV/nucl < E < 5 GeV/nucl 5 GeV/nucl < E < 30 GeV/nucl E > 30 GeV/nucl

  21. Z EM physics EM + hadronic physics water phantom GCR α SIH + 10 cm water Simulation results SIH + 10 cm water shielding The Binary Ion model can be activated also for energies higher than 10 GeV/nucl but the model is valid up to 10 GeV/nucl 1 GeV/nucl < E < 10 GeV/nucl E > 10 GeV/nucl GCR α GCR α

  22. E. M. physics E. M. physics + hadronic physics Simulation results SIH + 10 cm water shielding • Total energy deposit in the phantomfor every slice of the spectrum • Each contribution is weighted for the probability of the spectrum slice • The biggest contribution derives from: 700 MeV/nucl < E < 30GeV/nucl GCR α • The energy deposit of GCR α is not weighted with the probability to generate a GCR α with respect to GCR p (0.06) at this stage

  23. Z water phantom GCR α SIH + 10 cm water Simulation results SIH + 10 cm water shielding • Contribution of the energy deposit given by the GCR ion components: 12C, 16O, 28Si, 52Fe P Relative contribution to the equivalent dose Particle Equivalent dose (mSv) p1. α0.86 C 0.115 O 0.16 Si 0.06 Fe 0.106 α C Fe O Si Only electromagnetic physics active

  24. Z water phantom GCR p,α SIH + water Effect of different thicknesses • Energy deposit in the phantom: • SIH + 10 cm water / 5 cm water Empty triangle - 5 cm water Black circle – 10 cm water Energy deposit with respect to the depth in the phantom GCR p GCR α Doubling the shielding thickness corresponds to decreasing the energy deposited by 11% and 16% approximatelyfor p and α respectively.

  25. Z E.M. + hadronic physics water phantom GCR p GCR p,α SIH + water / poly E.M. physics Effect of different shielding materials • Comparison between water and polyethylene as shielding materials Energy deposit with respect to the depth in the phantom Black – 10 cm water polyethylene White – 10 cm water • The energy deposited in the phantom adopting water or polyethylene as shielding is the same • Kolmogorov-Smirnov test result: • p-value ≥ 0.95 • Similar results were obtained comparing the shielding properties of the two materials against other cosmic ray components

  26. Z SIH + 10 cm water SIH + 10 cm poly water phantom GCR p,α SIH + water / poly GCR p - Comparison water / polyethylene Energy deposit with respect to the depth in the phantom 130 MeV < E < 700 MeV 5 GeV < E < 30 GeV EM + hadronic physics active

  27. Z SIH + 10 cm water SIH + 10 cm poly water phantom GCR p,α SIH + water / poly GCR p - Comparison water / polyethylene Energy deposit with respect to the depth in the phantom E > 30 GeV Water and polyethylene have the same shielding behaviour EM + hadronic physics active

  28. Z water phantom water phantom GCR p,α, ions GCR p,α, ions Aluminum SIH + water Z Comparison with rigid Al structures • A simulation was performed to compare the shielding properties of an inflatable habitat with respect to a conventional rigid structure • Energy deposit of the GCR components in the phantom in the following configurations: • multilayer + 10 cm water • multilayer + 5 cm water • 4 cm Al • 2.15 cm Al

  29. GCR p SIH + 5 cm water 2.15 cm Al 4 cm Al SIH + 10 cm water Results Energy deposit with respect to the depth in the phantom • Kolmogorov-Smirnov test demonstrated that the shielding performance of the inflatable habitat concept is statistically equivalent to conventional solutions • SIH + 10 cm water does not differ from a 4 cm Al structure (p-value = 0.19) • SIH + 5 cm water shielding is not different from a 2.15 cm Al (p-value = 0.74).

  30. SIH + 10 cm water 4 cm Al GCR p Comparison 4 cm Al – SIH + 10 cm water Energy deposit with respect to the depth in the phantom 5 GeV < E < 30 GeV 130 MeV < E < 700 MeV EM + hadronic physics

  31. SIH + 10 cm water 4 cm Al GCR p Comparison 4 cm Al – SIH + 10 cm water Energy deposit with respect to the depth in the phantom E > 30 GeV EM + hadronic physics

  32. SIH + 10 cm water 4 cm Al GCR αComparison 4 cm Al – SIH + 10 cm water Energy deposit with respect to the depth in the phantom 700 MeV/nucl < E < 5 GeV/nucl 130 MeV/nucl < E < 700 MeV/nucl EM + hadronic physics

  33. SIH + 10 cm water 4 cm Al GCR αComparison 4 cm Al – SIH + 10 cm water Energy deposit with respect to the depth in the phantom 5 GeV/nucl < E < 30 GeV/nucl E > 30 GeV/nucl EM + hadronic physics

  34. SIH + 10 cm water 4 cm Al Comparison: SIH + 10 cm water / 4 cm Al • Total energy deposit in the phantomfor every slice of the spectrum • No difference between SIH + 10 cm water and 4 cm Al GCR α GCR p • The energy deposit of GCR α is not weighted with the probability to generate a GCR α with respect to GCR p (0.06) at this stage

  35. vacuum Shelter air vacuum SIH + 10 cm water Phantom Multilayer (28 layers) GCR and SPE particles SIH SPE shelter model • Dosimetric study of SPE p and α • Comparison of the energy deposit in the cases: Shelter • SIH + 10 cm water • SIH + 10 cm water + shelter Geant4 model Geant4 model • Scope: evaluation of the dosimetric effect of the shelter • All the results were obtained with simulation of 100 k events

  36. vacuum Shelter air vacuum SIH + 10 cm water Phantom Multilayer (28 layers) SPE particles Strategy Observation: SPE p and α with E > 130 MeV/nucl arrive to the shelter SPE p and αwith E > 400 MeV/nucl arrive to the phantom • Energy deposit of SPE in the configuration SIH + 10 cm water • generating SPE with the entire spectrum • generating SPE with E < 400 MeV/ nucl • generating SPE with E > 400 MeV/nucl • Energy deposit of SPE in the configuration: SIH + 10 cm water + shelter • generating SPE with E > 400 MeV/nucl • Calculate and compare the total energy deposit in the two configurations: • SIH + 10 cm water shielding • SIH + 10 cm water shielding + shelter

  37. Z water phantom SPE p SIH + 10 cm water SPE: Energy deposit in SIH + 10 cm water configuration • E.m. + hadronic physics (Bertini set) Energy deposit with respect to the depth in the phantom • 68 SPE p arrive to the phantom • 14 SPE α arrive to the phantom • E > 130 MeV/nucl arrive to the phantom • E < 130 MeV/nucl is the ~98% of the entire spectrum The energy deposit is not weighted with the probability to generate a SPE α with respect to SPE p (0.021)

  38. SPE energy spectrum with E> 400 MeV Z water phantom SPE p SIH + 10 cm water SIH + 10 cm water • 100 K SPE p with E < 400 MeV • E.m. + hadronic physics – Bertini set Energy distribution of primary particles Energy deposit with respect to the depth in the phantom SPE p Energy deposit

  39. Z water phantom SPE p SIH + 10 cm water SIH + 10 cm water • SPE p with E > 400 MeV • E.m. + hadronic physics – Bertini set Energy deposit (MeV) with respect to the depth in the phantom (cm) Energy distribution of primary particles Energy deposit MeV 100 K SPE p Depth (cm) cm

  40. SIH + 10 cm water – SPE p • Total energy deposit in the phantom Energy deposit (MeV) with respect to the depth in the phantom (cm) E < 400 MeV E > 400 MeV Sum of the two contributions

  41. Z water phantom SPE p SIH + 10 cm water SPE p, E> 400 MeV Energy deposit (MeV) with respect to the depth in the phantom (cm) • SPE p with E > 400 MeV • E.m. + hadronic physics – Bertini set • Comparison of the energy deposit • SIH + 10 cm water • SIH + 10 cm water + shelter SIH + 10 cm water SIH + 10 cm water + shelter 100 K events

  42. SPE p: results • Energy deposit in the phantom in the configuration SIH + 10 cm water shielding: 42.2 GeV • Energy deposit in SIH + 10 cm water + shelter: 22.47 GeV • The shelter limits the energy deposit in the phantom of about 50%

  43. Z Energy deposit (MeV) with respect to the depth in the phantom (cm) water phantom SPE α 100 k events SIH + 10 cm water SPE alpha E < 400 MeV E < 400 MeV/nucl SIH + 10 cm water SPE alpha • E > 130 MeV/nucl traverse SIH + 10 cm water shielding • E > 400 MeV/nucl traverse the shelter and arrive to the phantom • E < 400 MeV/nucl represents the 99.98 % of the entire spectrum • E.m. + hadronic physics – Bertini set SIH + 10 cm water

  44. SPE α - results Energy deposit (MeV) with respect to the depth in the phantom (cm) EM + hadronic physics Total energy deposit in the phantomwith the shelter = 33 % of the tot energy deposit without the shelter SIH + 10 cm water SIH + 10 cm water + shelter E > 400 MeV/nucl E > 400 MeV/nucl

  45. x = 0 - 3 m roof thickness Add a log on top with variable height x vacuum Moon soil GCR SPE beam x Phantom Energy deposit of GCR p in 4 cm Al configuration Energy deposit of GCR α in 4 cm Al configuration Planetary surface habitats – Moon - GCR GCR p GCR α

  46. Add a log on top with variable height x vacuum Moon soil GCR SPE beam x Phantom Planetary surface habitats – Moon SPE • Energy deposited in the phantom from solar event protons and α with E > 300 MeV/nucl • 105 SPE p and α • Both electromagnetic and hadronic physics (Bertini set) active

  47. Summary of the results • Simplified Inflatable Habitat + shielding • water / polyethylene are equivalent • hadronic interactions are significant • the larger contribution in the energy deposit in the phantom derives from intermediate energy range of GCR: 700 MeV/nucl < E < 30 GeV/nucl • The larger contribution in the energy deposit in the phantom derives from GCR p and α • Aluminum Vehicle • comparable to SIH • Moon Habitat • thick soil roof limits GCR and SPE exposure

  48. Comments • Present situation: • Relative comparison of shielding solutions • Next future • Understand the behaviour of the hadronic physics models more in depth to explain the results obtained • Generate GCR and SPE from a sphere isotropically • Calculation of absolute dose in the phantom • Substitute the phantom (water box) with an anthropomorphic phantom

  49. Comments • It is important to model accurately the hadronic interactions for radioprotection studies of astronauts • It is important to offer accurate hadronic physics models for protons, α, heavier ions (up to iron) as incident particles • Extensive validation of Geant4 hadronic physics models is required

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