REMSIM Geant 4 Simulation S Guatelli 1 B
REMSIM Geant 4 Simulation S. Guatelli 1, B. Mascialino 1, P. Nieminen 2, M. G. Pia 1 1. INFN Sezione di Genova 2. ESA - ESTEC www. ge. infn. it/geant 4/space/remsim 4 th Workshop on Geant 4 Bio-medical Developments and Geant 4 Physics Validation 14 th July 2005, Genova, Italy S. Guatelli – INFN Sezione di Genova
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 S. Guatelli – INFN Sezione di Genova
Scope of the REMSIM Geant 4 application The project takes place in the framework of the AURORA programme of the European Space Agency Scope Quantitative evaluation of the physical effects of space radiation in interplanetary manned missions Vision A first quantitative analysis of the shielding properties of some innovative conceptual designs of vehicle and surface habitats Comparison among different shielding options S. Guatelli – INFN Sezione di Genova
Summary of process products See S. Guatelli – INFN Sezione di Genova http: //www. ge. infn. it/geant 4/space/remsim/environment/artifacts. html
REMSIM Simulation Design S. Guatelli – INFN Sezione di Genova
Strategy of the Simulation Study Model the radiation spectrum according to current standards – simplified angular distribution to produce statistically meaningful results Vehicle concepts Simplified geometrical configurations retaining the essential characteristics for dosimetry studies Surface habitats Astronaut Physics modeled by Geant 4 – – – Electromagnetic processes Select appropriate models from the Toolkit + Hadronic processes Verify the accuracy of the physics models Distinguish e. m. and hadronic contributions to the dose Evaluate energy deposit/dose in shielding configurations – various shielding materials and thicknesses S. Guatelli – INFN Sezione di Genova
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 GCR: p, α, heavy ions at 1 AU Envelope of CREME 96 1977 and CREME 86 1975 solar minimum spectra 100 K primary particles, for each particle type Energy spectrum as in GCR/SPE Scaled according to fluxes for dose calculation SPE particles: p and α at 1 AU Envelope of CREME 96 October 1989 and August 1972 spectra Worst case assumption for a conservative evaluation S. Guatelli – INFN Sezione di Genova
Vehicle concepts SIH - Simplified Inflatable Habitat Two (simplified) options of vehicles studied Simplified Rigid Habitat A layer of Al (thickness suggested by Alenia) Modeled as a multilayer structure consisting of: § § Materials and thicknesses by ALENIA SPAZIO 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 The Geant 4 geometry model retains the essential characteristics of the vehicle concept relevant for a dosimetry study S. Guatelli – INFN Sezione di Genova
Surface Habitats Example: surface habitat on the moon Cavity in the moon soil + covering heap The Geant 4 model retains the essential characteristics of the surface habitat concept relevant to a dosimetric study Sketch and sizes by ALENIA SPAZIO S. Guatelli – INFN Sezione di Genova
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 30 cm 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 S. Guatelli – INFN Sezione di Genova Z
Selection of Geant 4 Physics Models E. M. physics: – Geant 4 Low Energy Package for p, α, ions and their secondaries – Geant 4 Standard Package for positrons Hadronic physics: – Elastic scattering – Inelastic Scattering - Protons, neutrons, pions: two alternative approaches (next slide) - Alpha: LEP model ( up to 100 Me. V), Binary Ion model (80 Me. V- 100 Ge. V/nucl), Tripathi and Shen cross sections active - Neutron fission and capture active S. Guatelli – INFN Sezione di Genova
Selection of Geant 4 Hadronic Physics Models Hadronic Physics for protons and α as primary particles Hadronic inelastic process Binary approach Bertini approach Low energy range (cascade + precompound + nuclear deexcitation) Binary Cascade ( up to 10. Ge. V ) Bertini Cascade ( up to 3. 2 Ge. V ) Intermediate energy range Low Energy Parameterised ( 8. Ge. V < E < 25. Ge. V ) Low Energy Parameterised ( 2. 5 Ge. V < E < 25. Ge. V ) High energy range ( 20. Ge. V < E < 100. Ge. V ) Quark Gluon String Model + hadronic elastic process S. Guatelli – INFN Sezione di Genova
SIH Study of vehicle concepts Incident spectrum of GCR particles Energy deposit in phantom due to electromagnetic interactions Add the hadronic physics contribution to the energy deposit on top vacuum Geant 4 model air Configurations • • GCR particles • • • phantom multilayer - SIH shielding S. Guatelli – INFN Sezione di Genova 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
Generating primary particles: strategy SIH + 10 cm water First step: – Generate GCR particles with the entire input energy spectrum GCR p Second step: – Generate GCR p and α with defined slices of the energy spectrum: • • – 130 Me. V/nucl < E < 700 Me. V/nucl < E < 5 Ge. V/nucl < E < 30 Ge. V/nucl E > 30 Ge. V/nucl Study the energy deposit in the phantom with respect to the slice of the energy spectrum of the primaries S. Guatelli – INFN Sezione di Genova GCR p with 5 Ge. V < E < 30 Ge. V
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 S. Guatelli – INFN Sezione di Genova
Simulation results – GCR p Energy deposit with respect to the depth in the phantom E. M. physics E. M. + hadronic physics – binary set E. M. + hadronic physics – bertini set water phantom SIH + 10 cm water Z 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%. S. Guatelli – INFN Sezione di Genova
Simulation results – GCR α Energy deposit with respect to the depth in the phantom E. M. physics E. M. + hadronic physics S. Guatelli – INFN Sezione di Genova water phantom SIH + 10 cm water Z The contribution of the hadronic interactions with respect to the electromagnetic one is statistically negligible ( Kolmogorov-Smirnov test result: p-value = 0. 95)
Simulation results SIH + 10 cm water shielding GCR p Energy deposit given by both e. m. and hadronic interactions in the phantom 130 Me. V – 700 Me. V – 5 Ge. V – 30 Ge. V E > 30 Ge. V S. Guatelli – INFN Sezione di Genova GCR α water phantom SIH + 10 cm water Z
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 Me. V < E < 30 Ge. V S. Guatelli – INFN Sezione di Genova GCR p
Simulation results SIH + 10 cm water shielding GCR α S. Guatelli – INFN Sezione di Genova GCR α SIH + 10 cm water 130 Me. V/nucl < E < 700 Me. V/nucl < E < 5 Ge. V/nucl < E < 30 Ge. V/nucl E > 30 Ge. V/nucl 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 water phantom Z
Simulation results SIH + 10 cm water shielding GCR α The Binary Ion model can be activated also for energies higher than 10 Ge. V/nucl but the model is valid up to 10 Ge. V/nucl 1 Ge. V/nucl < E < 10 Ge. V/nucl GCR α water phantom SIH + 10 cm water Z E > 10 Ge. V/nucl GCR α EM physics EM + hadronic physics S. Guatelli – INFN Sezione di Genova
Simulation results SIH + 10 cm water shielding GCR α E. M. physics + hadronic physics Total energy deposit in the phantom for every slice of the spectrum Each contribution is weighted for the probability of the spectrum slice The biggest contribution derives from: 700 Me. V/nucl < E < 30 Ge. V/nucl 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 S. Guatelli – INFN Sezione di Genova
Simulation results SIH + 10 cm water shielding water phantom GCR α SIH + 10 cm water Z Contribution of the energy deposit given by the GCR ion components: 12 C, 16 O, 28 Si, 52 Fe P α Relative contribution to the equivalent dose Particle Equivalent dose (m. Sv) Fe C O Si p α C O Si Fe 1. 0. 86 0. 115 0. 16 0. 06 0. 106 Only electromagnetic physics active S. Guatelli – INFN Sezione di Genova
Effect of different thicknesses GCR p, α Energy deposit in the phantom: – SIH + 10 cm water / 5 cm water Energy deposit with respect to the depth in the phantom GCR p water phantom SIH + water Z Empty triangle - 5 cm water Black circle – 10 cm water GCR α Doubling the shielding thickness corresponds to decreasing the energy deposited by 11% and 16% approximately for p and α respectively. S. Guatelli – INFN Sezione di Genova
Effect of different shielding materials GCR p, α water phantom SIH + water / poly Z Comparison between water and polyethylene as shielding materials Energy deposit with respect to the depth in the phantom E. M. + hadronic physics GCR p 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 E. M. physics S. Guatelli – INFN Sezione di Genova • Similar results were obtained comparing the shielding properties of the two materials against other cosmic ray components
GCR p - Comparison water / polyethylene GCR p, α water phantom SIH + water / poly Energy deposit with respect to the depth in the phantom SIH + 10 cm water SIH + 10 cm poly 130 Me. V < E < 700 Me. V 5 Ge. V < E < 30 Ge. V EM + hadronic physics active S. Guatelli – INFN Sezione di Genova Z
GCR p - Comparison water / polyethylene GCR p, α water phantom SIH + water / poly Z Energy deposit with respect to the depth in the phantom SIH + 10 cm water SIH + 10 cm poly E > 30 Ge. V EM + hadronic physics active S. Guatelli – INFN Sezione di Genova Water and polyethylene have the same shielding behaviour
Comparison with rigid Al structures A simulation was performed to compare the shielding properties of an inflatable habitat with GCR p, α, ions 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 S. Guatelli – INFN Sezione di Genova water phantom SIH + water Z water phantom GCR p, α, ions Aluminum Z
Results Energy deposit with respect to the depth in the phantom GCR p SIH + 5 cm water Kolmogorov-Smirnov test demonstrated that the shielding performance of the inflatable habitat concept is statistically equivalent to conventional solutions 2. 15 cm Al 4 cm Al SIH + 10 cm water S. Guatelli – INFN Sezione di Genova 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).
GCR p Comparison 4 cm Al – SIH + 10 cm water Energy deposit with respect to the depth in the phantom 130 Me. V < E < 700 Me. V EM + hadronic physics S. Guatelli – INFN Sezione di Genova 5 Ge. V < E < 30 Ge. V 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 Ge. V EM + hadronic physics SIH + 10 cm water 4 cm Al S. Guatelli – INFN Sezione di Genova
GCR α Comparison 4 cm Al – SIH + 10 cm water Energy deposit with respect to the depth in the phantom 130 Me. V/nucl < E < 700 Me. V/nucl < E < 5 Ge. V/nucl EM + hadronic physics SIH + 10 cm water 4 cm Al S. Guatelli – INFN Sezione di Genova
GCR α Comparison 4 cm Al – SIH + 10 cm water Energy deposit with respect to the depth in the phantom 5 Ge. V/nucl < E < 30 Ge. V/nucl E > 30 Ge. V/nucl EM + hadronic physics SIH + 10 cm water 4 cm Al S. Guatelli – INFN Sezione di Genova
Comparison: SIH + 10 cm water / 4 cm Al Total energy deposit in the phantom for every slice of the spectrum No difference between SIH + 10 cm water and 4 cm Al SIH + 10 cm water 4 cm Al GCR p 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 S. Guatelli – INFN Sezione di Genova
SIH SPE shelter model Dosimetric study of SPE p and α Shelter Geant 4 model Shelter vacuum Comparison of the energy deposit in the cases: • SIH + 10 cm water + shelter air Scope: evaluation of the dosimetric effect of the shelter vacuum All the results were obtained with simulation of 100 k events GCR and SPE particles SIH + 10 cm water Multilayer (28 layers) S. Guatelli – INFN Sezione di Genova Phantom
Strategy Observation: SPE p and α with E > 130 Me. V/nucl arrive to the shelter SPE p and α with E > 400 Me. V/nucl arrive to the phantom Shelter vacuum SPE particles SIH + 10 cm water Multilayer (28 layers) Energy deposit of SPE in the configuration SIH + 10 cm water – generating SPE with the entire spectrum – generating SPE with E < 400 Me. V/ nucl – generating SPE with E > 400 Me. V/nucl Energy deposit of SPE in the configuration: SIH + 10 cm water + shelter – generating SPE with E > 400 Me. V/nucl Calculate and compare the total energy deposit in the two configurations: – SIH + 10 cm water shielding + shelter S. Guatelli – INFN Sezione di Genova air Phantom
SPE: Energy deposit in SIH + 10 cm water configuration SPE p water phantom SIH + 10 cm water Z 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 Me. V/nucl arrive to the phantom • E < 130 Me. V/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) S. Guatelli – INFN Sezione di Genova
SIH + 10 cm water SPE p 100 K SPE p with E < 400 Me. V E. m. + hadronic physics – Bertini set Energy distribution of primary particles SPE energy spectrum SPE p with E> 400 Me. V Energy deposit S. Guatelli – INFN Sezione di Genova water phantom SIH + 10 cm water Z Energy deposit with respect to the depth in the phantom
SIH + 10 cm water phantom SPE p with E > 400 Me. V E. m. + hadronic physics – Bertini set Energy deposit Me. V Depth (cm) S. Guatelli – INFN Sezione di Genova Z (Me. V) with respect to the depth in the phantom (cm) Energy deposit Energy distribution of primary particles 100 K SPE p SIH + 10 cm water cm
SIH + 10 cm water – SPE p Total energy deposit in the phantom Energy deposit (Me. V) with respect to the depth in the phantom (cm) E < 400 Me. V E > 400 Me. V Sum of the two contributions S. Guatelli – INFN Sezione di Genova
SPE p, E> 400 Me. V Energy deposit (Me. V) with respect to the depth in the phantom (cm) SIH + 10 cm water + shelter SPE p water phantom SIH + 10 cm water Z SPE p with E > 400 Me. V E. m. + hadronic physics – Bertini set 100 K events S. Guatelli – INFN Sezione di Genova Comparison of the energy deposit – SIH + 10 cm water + shelter
SPE p: results Energy deposit in the phantom in the configuration SIH + 10 cm water shielding: 42. 2 Ge. V Energy deposit in SIH + 10 cm water + shelter: 22. 47 Ge. V The shelter limits the energy deposit in the phantom of about 50% S. Guatelli – INFN Sezione di Genova
SIH + 10 cm water SPE alpha E > 130 Me. V/nucl traverse SIH + 10 cm water shielding E > 400 Me. V/nucl traverse the shelter and arrive to the phantom SPE α water phantom SIH + 10 cm water Energy deposit (Me. V) with respect to the depth in the phantom (cm) 100 k events SPE alpha E < 400 Me. V/nucl represents the 99. 98 % of the entire spectrum E < 400 Me. V/nucl SIH + 10 cm water E. m. + hadronic physics – Bertini set S. Guatelli – INFN Sezione di Genova Z
SPE α - results Energy deposit (Me. V) with respect to the depth in the phantom (cm) EM + hadronic physics SIH + 10 cm water E > 400 Me. V/nucl SIH + 10 cm water + shelter E > 400 Me. V/nucl Total energy deposit in the phantom with the shelter = 33 % of the tot energy deposit without the shelter S. Guatelli – INFN Sezione di Genova
Planetary surface habitats – Moon - GCR Add a log on top with variable height x GCR p vacuum Moon soil GCR SPE beam GCR α x Phantom x = 0 - 3 m roof thickness S. Guatelli – INFN Sezione di Genova Energy deposit of GCR p in 4 cm Al configuration Energy deposit of GCR α in 4 cm Al configuration
Planetary surface habitats – Moon SPE Energy deposited in the Add a log on top with variable height x vacuum Moon soil phantom from solar event protons and α with E > 300 Me. V/nucl 105 SPE p and α Both electromagnetic and hadronic physics (Bertini set) active Particle GCR SPE beam x Phantom S. Guatelli – INFN Sezione di Genova Energy deposit (Ge. V) 0. 5 m thick roof Energy deposit (Ge. V) 3. 5 m thick roof SPE p 5434. 14. 9 SPE α 12. 0. 37
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 Me. V/nucl < E < 30 Ge. V/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 S. Guatelli – INFN Sezione di Genova
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 S. Guatelli – INFN Sezione di Genova
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 Geant 4 hadronic physics models is required S. Guatelli – INFN Sezione di Genova
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