radioprotection for interplanetary manned missions
DESCRIPTION
www.ge.infn.it/geant4/space/remsim. Radioprotection for interplanetary manned missions. R. Capra 1 , S. Guatelli 1 , B. Mascialino 1 , P. Nieminen 2 , M. G. Pia 1 INFN, Genova, Italy ESA-ESTEC, Noordwijk, The Netherlands. Geant4-SPENVIS Workshop 3-7 October 2005 Leuven, Belgium. - PowerPoint PPT PresentationTRANSCRIPT
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Geant4-SPENVIS Workshop3-7 October 2005Leuven, Belgium
www.ge.infn.it/geant4/space/remsim
Radioprotection for interplanetary Radioprotection for interplanetary manned missionsmanned missions
R. Capra1, S. Guatelli1, B. Mascialino1, P. Nieminen2, M. G. Pia1
1. INFN, Genova, Italy
2. ESA-ESTEC, Noordwijk, The Netherlands
Thanks to ALENIA SPAZIO, C. Lobascio and team
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Context
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, M.G. Pia – INFN Sezione di Genova
Scope of the project
ScopeScope
VisionVision A first quantitative analysisquantitative analysis of the shielding properties shielding properties of some innovative conceptual designs of vehicle vehicle and
surface habitatssurface habitats
Comparison among different shielding options
Quantitative evaluation of the physical effects of space radiation in interplanetary manned missions
The project deals with studies relevant to the AURORA programme
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Software strategy
The object oriented technology has been adopted– Suitable to long term application studies – Openness of the software to extensions and evolution– It facilitates the maintainability of the software over a long time scale
Geant4 has been adopted as Simulation Toolkit because it is– Open source, general purpose Monte Carlo code for particle transport
based on OO technology– Versatile to describe geometries and materials– It offers a rich set of physics models
The data analysis is based on AIDA– Abstract interfaces make the software system independent from any
concrete analysis tools– This strategy is meaningful for a long term project, subject to the future
evolution of software tools
S. Guatelli, M.G. Pia – INFN Sezione di Genova
QualityQuality and reliabilityreliability of the software are essential requirements for a critical domain like radioprotection in space
Iterative and incremental process model– Develop, extend and refine the software in a series of steps– Get a product with a concrete value and produce results at each step– Assess quality at each step
Rational Unified Process (RUP) adopted as process framework– Mapped onto ISO 15504
Software process
adopt a rigorous software process
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Summary of process products
See http://www.ge.infn.it/geant4/space/remsim/environment/artifacts.html
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Architecture
Driven by goals deriving from the VisionVision
Design an agileagile system– capable of providing first indications for the evaluation of vehicle
concepts and surface habitat configurations within a short time scale
Design an extensibleextensible system – capable of evolution for further more refined studies, without
requiring changes to the kernel architecture
Documented in the Software Architecture Document
http://www.ge.infn.it/geant4/space/remsim/design/SAD_remsim.html
S. Guatelli, M.G. Pia – INFN Sezione di Genova
REMSIM Simulation Design
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Physics 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
Strategy of the Simulation Study
Simplified geometrical geometrical configurationsconfigurations retaining the essential characteristicsessential characteristics for dosimetry studies
Electromagnetic processes
+ Hadronic processes
Model the radiation spectrum according to current standards– Simplified angular distribution to produce statistically meaningful results
Evaluate energy deposit/doseenergy deposit/dose in shielding configurations– various shielding materials and thicknesses
Vehicle concepts
Surface habitats
Astronaut
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Space radiation environmentGalactic Cosmic Rays
– Protons, α particles and heavy ions (C -12, O -16, Si - 28, Fe - 52)Solar Particle Events
– Protons and α particles
Envelope of CREME96 1977 and CREME86 1975 solar minimum spectra
SPE particles: p and αGCR: p, α, heavy ions
Envelope of CREME96 October 1989 and August 1972 spectra
at 1 AU at 1 AU
Worst case assumption for a conservative evaluationWorst case assumption for a conservative evaluation
100K primary particles, for each particle typeEnergy spectrum as in GCR/SPE
Scaled according to fluxes for dose calculation
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Vehicle concepts
The Geant4 geometry model retains the essential characteristics of the vehicle concept relevant for a dosimetry study
Materials and thicknesses by ALENIA SPAZIO
Modeled as a multilayer structure 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
SIH - Simplified Inflatable Habitat
Simplified Rigid Habitat
A layer of Al (structure element of the ISS)
Two (simplified) options of vehicles studied
Simplified Inflatable Habitat
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Surface Habitats
Use of local material
Cavity in the moon soil + covering heap
The Geant4 model retains the essential characteristics of the
surface habitat concept relevant to a dosimetric study
Sketch and sizes by ALENIA SPAZIO
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Astronaut Phantom
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
30 cm Z
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
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Selection of Geant4 EM Physics Models
Geant4 Low Energy Package for p, α, ions and their secondaries
Geant4 Standard Package for positrons
Verification of the Geant4 e.m. physics processes with respect to protocol data (NIST reference data)
“Comparison of Geant4 electromagnetic physics models against the NIST reference data”, IEEE Transactions on Nuclear Science, vol. 52 (4), pp. 910-918, 2005
The electromagnetic physics models chosen are accurate
Compatible with NIST data within NIST accuracy (p-value > 0.9)
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Selection of Geant4 Hadronic Physics Models
Hadronic Physics for protons and α as incident particles
Hadronic inelastic process
Binary set Bertini set
Low energy range
(cascade + precompound + nuclear deexcitation)
Binary Cascade
( up to 10. GeV )
Bertini Cascade
( up to 3.2 GeV )
Intermediate energy rangeLow Energy Parameterised
( 8. GeV < E < 25. GeV )
Low Energy Parameterised
( 2.5 GeV < E < 25. GeV )
High energy range
( 20. GeV < E < 100. GeV )Quark Gluon String Model Quark Gluon String Model
+ hadronic elastic process
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Study of vehicle concepts
Incident spectrum of GCR particles
Energy deposit in phantom due to electromagnetic interactions
Add the hadronic physics contribution on top
GCR particles
vacuum air
phantom
multilayer - SIH shielding
Geant4 model
• 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
ConfigurationsConfigurations
inflatable habitat
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Generating primary particles
First step:– Generate GCR particles with the
entire spectrum
Second step:– Generate GCR p and α with defined defined
slices of the spectrum:slices of the 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
SIH + 10 cm water
GCR p with 5 GeV < E < 30 GeV
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Electromagnetic and hadronic interactions
e.m. physicse.m. + Bertini sete.m. + Binary set
GCR
vacuum air
phantommultilayer - SIH 10 cm water
shieldingGCR p
100 k events
100 k events
GCR α
Adding the hadronic interactions on top of the e.m. interactions increase the energy increase the energy deposit in the phantom by ~ 25 %deposit in the phantom by ~ 25 %
The contribution of the hadronic interactions looks negligible in the calculation of the energy deposit
e.m. physicse.m. + Binary ion set
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Total energy deposit in the phantom of each slice of the energy spectrum
The largest contribution derives from the intermediate energy range:
700 MeV < E < 30 GeV700 MeV < E < 30 GeV
Simulation results SIH + 10 cm water shielding
GCR p
E.M. contribution
Hadronic contribution
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Total energy deposit in the phantom for every slice of the spectrum
Each contribution is weighted for the probability of the spectrum slice
The largest contribution derives from:
700 MeV/nucl < E < 30GeV/nucl700 MeV/nucl < E < 30GeV/nucl
Simulation results SIH + 10 cm water shielding
GCR α
E. M. physicsE. M. physics + hadronic physics
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Shielding materialsComparison between
– Water– Polyethylene
Equivalent shielding results
GCR
vacuum air
phantommultilayer - SIH water / poly
shielding
10 cm water10 cm polyethylene
e.m. physics + Bertini set
e.m. physics only
GCR p 100 k events
Energy deposit given by slices of the GCR p spectrum
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Shielding thicknessGCR
vacuum air
phantom
multilayer - SIH 5 / 10 cm watershielding
10 cm water5 cm water
GCR p
100 k eventse.m. physics+ Bertini set
e.m. physics+ hadronic physics
10 cm water5 cm water
GCR α
100 k events
Doubling the shielding thickness decreases the energy deposit by ~10%~10%
Doubling the shielding thickness decreases the energy deposit ~ 15%15%
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Comparison of inflatable and rigid habitat concepts
Aluminum layer replacing the inflatable habitat
– based on similar structures as in the ISS
Two hypotheses of Al thickness– 4 cm Al– 2.15 cm Al
The shielding performance of the inflatable habitat is equivalent to conventional solutions
GCR
vacuum air
phantom
Al structure
2.15 cm Al
10 cm water
5 cm water
4 cm Al
100 k events
GCR p
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Comparison: SIH + 10 cm water / Al Total energy deposit in the phantom for every slice of the spectrum
No difference between SIH + 10 cm water and 4 cm AlSIH + 10 cm water4 cm Al
GCR pGCR α
S. Guatelli, M.G. Pia – INFN Sezione di Genova
The dose contributions from proton and α GCR components result significantly larger than for other ions
Effects of cosmic ray components ProtonsProtons
αα
O-16O-16
C-12C-12
Si-28Si-28Fe-52Fe-52
Particle Equivalent dose (mSv)
Protons 1.
α 0.86
C-12 0.115
O-16 0.16
Si-28 0.06
Fe-52 0.106
Relative contribution to the equivalent dose from some cosmic
rays components
e.m. physics processes only
100 k events
GCR
vacuum air
phantommultilayer - SIH 10 cm water
shielding
Depth in the phantom (cm)
S. Guatelli, M.G. Pia – INFN Sezione di Genova
shielding
multilayer shielding
phantom
Incidentradiation
vacuum airSPE shelter
SPE shelter modelInflatable habitat + additional 10. cm water shielding + SPE shelter
Comparison of the energy deposit in the cases:– SIH + 10 cm water shielding– SIH + 10 cm water shielding + SPE shelter
Geant4 model
Shelter
SIH
Approach:
Study the e.m. contribution to the energy deposit
Add on top the hadronic contribution
S. Guatelli, M.G. Pia – INFN Sezione di Genova
SPE: Energy deposit in SIH + 10 cm water configuration
100K SPE p and αE.m. + hadronic physics (Bertini set)
• 68 SPE protons reach the phantom
• 14 SPE alpha reach the phantom
• E > 130 MeV/nucl reach the astronaut (~2.8% of the entire spectrum)
The contribute of alpha is not weighted
waterphantom
SIH+ 10 cm water
SPE p,α
Z
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Strategy
Observation: SPE p and α with E > 130 MeV/nucl reach the shelterSPE p and α with E > 400 MeV/nucl reach the phantom ( < 0.3% of the entire spectrum)
waterphantom
SIH+ 10 cm water
SPE p,α
ZShelter
The shelter shields ~ 50% of the energy deposited by GCR p ~ 67 % of the energy deposited by GCR α
escaping the SIH shielding
Energy deposit (MeV) with respect to the depth in the phantom (cm)
E < 400 MeVE > 400 MeV
Sum of the two contributionsSum of the two contributions
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Moon surface habitats
Add a log on top with variable height x
x
vacuum moonsoil
GCR SPEbeam
Phantom
x = 0 - 3 m roof thickness
Energy deposit (GeV)in the phantom vs roof thickness (m)
4 cm Al
4 cm Al
100 k events
GCR pGCR α
e.m. + hadronic physics (Bertini set)
Moon as an intermediate step in the exploration of Mars
Dangerous exposure to Solar Particle Events
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Planetary surface habitats – Moon - SPE
E < 300 MeV stopped by the shielding
Energy deposit resulting from SPE with E > 300 MeV / nucl
The energy deposit of SPE α is weighted according to the flux with respect to SPE protons
The roof limits the exposure to SPE particles
SPE p – 0.5 m roof
SPE α– 0.5 m roof
SPE p – 3.5 m thick roof
SPE α – 3.5 m thick roof
e.m. + hadronic physics (Bertini set)
100 k events
Energy deposit in the phantom given by Solar Particle protons and α particles
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Comments on the results
Simplified Inflatable Habitat + shielding– water / polyethylene are equivalent as shielding material– optimisation of shielding thickness is needed– hadronic interactions are significant– an additional shielding layer, enclosing a special shelter zone, is
effective against SPE
The shielding properties of an inflatable habitat are comparable to the ones of a conventional aluminum structure
Moon Habitat– thick soil roof limits GCR and SPE exposure– its shielding capabilities against GCR are better than conventional
Al structures similar to ISS
S. Guatelli, M.G. Pia – INFN Sezione di Genova
Future
Latest development:the water phantom has been replaced by an anthropomorphicphantom
Next steps:– 3D model of the experimental set-up– Isotropic generation of GCR and SPE – Calculation of the energy deposit and of the dose in the
organs of the anthropomorphic phantom
GCR p, 106 events
phantom