space radiation environment & geant 4/gras simulations in sr2s
DESCRIPTION
Space Radiation Superconductive Shield (SR2S) is an EU funded FP7 project which is researching new technology to protect astronauts in space from radiation. On 9th April 2014 in Torino, Italy, SR2S held their first conference to give an update on the project so far. For more information visit: www.sr2s.eu Twitter - @SR2SMarsTRANSCRIPT
Radiation Environment and
Geant4/GRAS Simulations in SR2S
April 9th, 2014
Martina Giraudo
Marco Vuolo
• SR2S introductory VIDEO
• Space radiation Environment
• HZE biological effects
• TAS-I simulation framework
• Simulated Environment
• Geometrical Model
• Simulation Plan & Future Works
Summary
SR2S Introductory Video
• Cancer risk caused by radiation exposure is the main obstacle to interplanetary travel
– No simple and effective countermeasures
– Significant uncertainties
• Possible solutions:
– Optimization of space missions length
– MITIGATION MEASURES: SHIELDING and biological countermeasures
Introduction
Space Radiation in Deep-Space
• Space radiation hitting the crew: HZE, primary protons and secondary protons, neutrons, and recoil nuclei
• Secondary particles produced as radiation interacts with matter
• Whole body doses of 1 to 2 mSv/day accumulated in interplanetary space
Two main components : SPE & GCR
Solar particle events (SPEs)
• Mainly energetic protons, helium nuclei and heavier nuclei
• Highest intensity at solar maximum
• Relative short fluxes of particles
• Energies from 1 to 100 MeV
• Not currently predictable
• Easily shielded by passive
and active shields
Galactic cosmic rays (GCR)
• Continuous source
• Energies ranging from ~10
MeV n-1 to ~ 1012 MeV n-1
• High-LET radiation
• Biological effects poorly
known
• Most significant deep-space
missions radiation hazard
• Modulated by the Sun cycle
• Not easily shielded
Space Radiation in Deep-Space
Deep Space Effective Dose Estimations
• When considering passive shielding option:
– SPE easily shielded
– GCR requires enormous mass to be shielded because of high energies and secondary radiation
• Mission at solar maximum
• Thick shielding:
– Mass problems to spacecraftlaunch systems
– Bad GCR effective dose reduction
Current shield approach:
NOT a solution
Annual GCR Effective doses or NASAEffective dose in deep space vs. depth ofshielding for males. Values for solarminimum and maximum are shown
Radiation Biological Risk to the Crew
• Carcinogenesis (morbidity and mortality risk)
• Acute Radiation Risks – sickness or death
• Acute and Late Central Nervous System (CNS) risks
• Chronic & Degenerative Tissue Risks
Differences in biological damage of heavy nuclei vs x-rays Earth-based data � New knowledge on risks must be obtained
CONTROL
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HZE effects vs low-LET radiation effects
• HZE produce densely ionizing tracks of damage
• Complex DNA breaks, “clusters”containing mixtures of more kinds of damage– Poor damage repair
– Cell death more frequent
“Cancer risk from exposure to galactic cosmic rays: implications for space
exploration by human beings” Francis A Cucinotta, Marco Durante
• Drugs– applicable for extended period of time and suitable for high-LET radiation
– no significant side effects, including those on behavior
– stable chemical composition (easy handling and storage)
– better if suitable for oral administration and rapidly absorbed and distributed throughout the body
• Dietary supports– Space environmental factors leading to increased oxidative stress �
deployment of antioxidant capacity in astronauts
– antioxidant rich diet � decreased risk of several diseases, cancer included
– Possible antioxidant radioprotectors: vitamin E and C, melatonin and selenium
• Appropriate crew selection
Biological Countermeasures
SR2S Geant4/GRAS simulation
• Simulation framework
• Environment models
• Geometrical model
– Coils & cables
– Mechanical structures
– Habitat
– Detectors
• Simulation plan
TAS-I Monte Carlo Simulation Framework
Simulations are simultaneously run on different processors
Results are saved in ROOT histogram for post processing
Geant4 Radiation Analysis for Space
MC toolkit for the simulation of interaction of particles in matter
• GCR– CRÈME96– Solar minimum condition– No Scaling factor: variation from 1 AU to Mars Orbit is negligible for
SR2S scope (see new measurements from MER and MSL missions)
• SPE– SUPERFLARE fluence
• CREME86 (M11 - M1) representative of period 1955 to 1972 (as envelope of events of Feb ‘56 and Aug ‘72) composite worst case (hour) flare flux and mean ions composition;
• OMERE worst hours flare fluxes of: Oct ‘89, Jul ‘00, Oct ’03
– Average flux on 1 year interplanetary mission• ESP model @ 99% confidence level
• TRAPPED PARTICLES: neglected in SR2S
Modeled Environment
• Compromise between accuracy of the geometrical details and computational time
– Complex geometries simplified to obtain homogeneous Geant4 materials with average elemental compositions
– Habitat modeled using average values of thickness and density
– Mechanical structures simplified
Geometric Model
Geometric Model: Mechanical Structures Materials
Solid Hydrogen equivalent mass
Structural Titanium equivalent mass
Fuel Tank
Second Columbus module
Geometric Model: Mechanical Structure & SC Cable
Titanium
Bars
Ti equivalent
in mass
Solid
Hydrogen
• In this way computational time is saved and no significant accuracy is lost
• As soon as the mechanical structure is finalized the geometry GDML files will be easily updated.
SR2S Toroidal Configuration: Sectoring Analysis
Detector
ICRU SPHERE
Used Detectors: ICRU Sphere in three different positionICRU Sphere structure and composition:
BFO 2 mm
SKIN 2mm150 mm
100 mm
Skin � G4_SKIN_ICRP*Body � G4_TISSUE_SOFT_ICRU-4*BFO � G4_TISSUE_SOFT_ICRU-4*Organs � G4_TISSUE_SOFT_ICRU-4*
*http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/ForApplicationDeveloper/html/apas08.html
Magnetic Field Configuration
120 CoilsBmax= 3.53 TBL= 7.47 Tm
Magnetic field Validation : Analytic model vs. Geant4
Perfect matching between analytical previsions and simulation results
Magnetic field Validation : Analytic model vs. Geant4
Magnetic field Validation : Analytic model vs. Geant4
1. ICRU sphere in free space
2. Columbus habitat only
SR2S Simulation Plan 1/5
3. Columbus habitat and magnetic field only
4. Columbus habitat, active shielding structures and magnetic field ON
SR2S Simulation Plan 2/5
5. Columbus habitat with active shielding structures and NO magnetic field
6. Columbus habitat surrounded by passive shielding rich in H equivalent in mass to the active one
SR2S Simulation Plan 3/5
• Doses have been already calculated for every considered radiation environment components for:
– ICRU sphere in deep space
– Example of deep space habitat in deep space
• Results will include data on:
– Doses - Equivalent Doses
– Fluxes - Fluences
SR2S Simulation Plan 4/5
ICRU SPHERE IN FREESPACE
• Results will be available by the end of May and will permit a first evaluation of the active radiation shielding
• Other evaluations will have to be performed once the design of the mechanical structure is finalized
SR2S Simulation Plan 5/5
• No actual passive shielding solutions to GCR
• Investigation of magnetic active shielding as a possible way to overcome the problem
• Necessity to further develop the involved technology, focusing on:
– Optimization of structures
– Safety and reliability
• Necessity to have biological data for GCR
Conclusions
THE ENDThank you for your attention
Questions?
BACK UP SLIDES
SR2S Environment: Superflare differential flux
1,00E-06
1,00E-05
1,00E-04
1,00E-03
1,00E-02
1,00E-01
1,00E+00
1,00E+01
1,00E+02
1,00E+03
1,00E+04
1,00E+05
1,00E+06
1,00E+07
1,00E-01 1,00E+00 1,00E+01 1,00E+02 1,00E+03 1,00E+04 1,00E+05
pro
ton
s.M
eV
-1.c
m-2
.s-1
MeV
Superflare Differential Flux
CREME86 M11-M1
Oct 89 worst hour
Oct 03 worst hour
Jul 00 worst hour
Aug 72 worst hour
SR2S Environment: GCR differential fluxes
MissionTotal Mission
DurationOutbound Stay Return
Total Days in Deep-Space
Lagrange’s Points [LEM2]
200 - - - 200
NEA 410 ~170 30 ~210 ~380
MARS TITO mission
501 228 - 273 501
MARS Short Stay 545 224 30 291 515
MARS Long Stay(minimum
energy)919 224 458 237 461
MARS Long Stay(fast transit)
879 150 619 110 260
Considered Mission Scenarios
The Hydrogen GCR flux at 1AU predicted by CREME96 and CREME2009
particle flux models for the solar minimum
CRÈME 96 vs CRÈME2009
Differential GCR Protons Fluence for Different Scenarios
• Astronauts who are on missions to the ISS, the moon, or Mars are exposed to ionizing radiation with effective doses in the range from 50 to 2,000 mSv
• The evidence of cancer risk from ionizing radiation is extensive for radiation doses that are above about 50 mSv.
Doses in Space
HZE
Differences in biological damage of heavy nuclei with x-rays Earth-based data �New knowledge on risks must be obtained
Possible acute or late damages to CNS, caratacts, heart tissues, etc, from low dose rate (< 50 mGy/h) of HZE
CONTROL
IRON IRRADIATED
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• International overview:– ESA: dose limits based on ICRP recommendations for ground-base
workers with some modifications
– NASA, JAXA: age and gender dependent limits for late effects
• Career Limits based on a 10 years exposure
LEO Exposure Limits – Career Effective Dose Limits
Uncertainties in Risk Projection in Radiation Exposure
From Cucinotta and Durante, 2011
Magnetic field Validation : Analytic model vs. Geant4