Barghouty, Nasser

NASA Technical Reports Server

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National Aeronautics and Space Administration
SCIENCE & TECHNOLOGY OFFICE
Nasser Barghouty 
Astrophysics Office, NASA-Marshall Space Flight Center
11th Geant4 Space Users Workshop, Hiroshima, Japan, August  26-28, 2015
Radiation Transport and Space-Radiation Related Efforts
at NASA’s Marshall Space Flight Center
https://ntrs.nasa.gov/search.jsp?R=20150018355 2019-08-31T06:27:25+00:00Z
211th G4SUW Presentation August 26, 2015
Space Radiation: The Drive & The Challenges
Effective shielding against the combined 
effects of GCRs and SEPs can be mass 
prohibitive
Shielding effectiveness of new, potential 
shielding materials (or combinations 
thereof) is not well characterized
Little data to guide dose and risk 
assessment models 
Known, large uncertainties and 
variabilities in radiobiological effects
Other uncertainties and variabilities?
(e.g., in generalization and scale-up of 
shielding or protection solutions)
A NASA strategic radiation protection 
guideline is the:
“Demonstration of shielding concepts 
providing radiation protection focusing on 
light-weight multi-functional structure-
capable materials that can provide 
GCR/SPE protection while providing other 
functionalities such as thermal insulation, 
structural integrity, and/or MMOD 
protection.” 
The Drive
311th G4SUW Presentation August 26, 2015
Space Radiation: The Path Forward
No one center or group (in academia or in the private sector) can 
realistically implement this integrated approach on its own!
• TA02 and TA03: coordination with 
radiation protection measures for 
nuclear propulsion and power systems; 
• TA03: survivability of solar power cells 
and other power system components in 
extreme radiation environments; 
• TA06: astronaut health; 
• TA08: instrumentation for particles, 
fields, and waves; 
• TA10: use of boron nitride nanotubes for 
protection against radiation; and 
• TA12: materials and structures for 
radiation shielding.
NASA’s technology roadmaps 
call  for an integrated approach 
in radiation protection
411th G4SUW Presentation August 26, 2015
Two main sources of ionizing radiation:
Galactic Cosmic Rays (GCR)
Protons + almost all other nuclei
Low intensity (~ 1 cm-2)
High-energy (peaks at 500 MeV/N)
Sun-modulated by a factor ~4
Isotropic
Solar Energetic Particles (SEP)
Mostly protons
High intensity (~ 107 cm-2)
Lower energy (~ 100-200 MeV)
Random 
Directional
Space Radiation: Natural Sources
511th G4SUW Presentation August 26, 2015
Space Radiation: Shielding effectiveness (how certain?)
Materials vary in their ability to shield 
against GCR nuclei
Polymeric based materials tend to 
be most effective - but their 
structural and safety properties 
remain poor or poorly known
Aluminum, like all metals, is a poor 
GCR shield
Regolith is not that much better 
either!
611th G4SUW Presentation August 26, 2015
Space Radiation: Uncertainties in radiobiological effects
Large uncertainties -and variabilities-
in the radiation quality factor is seen 
as a main hindrance toward reliable 
dose and risk estimates 
These can be captured mathematically
if we model the quality factor as an 
Ornstein-Uhlenbeck process, 
with a corresponding PDF of the form,
711th G4SUW Presentation August 26, 2015
Space Radiation: Marshall’s Current Projects in…
• Monitoring & Detection
protons- TaSEPS
neutrons- ANS
• Forecasting
Mag4
• Modeling & Simulation
Geant4-based
• Radiation-Smart Structures
Geant4-informed
Bastille Day (2000 July 14) Flare, Coronal Mass 
Ejection and Solar Energetic Particle Event
811th G4SUW Presentation August 26, 2015
Space Radiation: Monitoring & Detection
• Marshall scientists and engineers develop state-of-the-art charged 
particle and neutral particle detectors suitable for the harsh 
environments of space
-Trapped and Solar Energetic Particle Spectrometer (TaSEPS): TaSEPS is a 
compact wide dynamic range charged particle spectrometer for measuring trapped 
and solar energetic protons by combing scintillation and Cherenkov techniques in 
a single CsI crystal that extends the dynamic range and reduces the mass and 
power requirements
Planned for an ISS flight demonstration
911th G4SUW Presentation August 26, 2015
Space Radiation: Monitoring & Detection
• Marshall scientists and engineers develop state-of-the-art charged 
particle and neutral particle detectors suitable for the harsh 
environments of space:
-Advanced Neutron Spectrometer (ANS): is a new instrument technique being 
developed to meet NASA’s requirements to monitor the radiation exposure due to 
secondary neutrons for future crewed missions. New instrument designs are 
needed to achieve the measurement performance requirements that fit within the 
resource limits of exploration missions beyond Earth’s protective magnetic field
Plastic and Li-Gd-B scintillator
n + 6Li  → 3H + 4He
Q  = 4.78 
n + Gd → Gd* + γ
Q  = [0,2]
n + 10B → 7Li + 4He
Q  = 2.73 (93%) 
or 2.25 (7%) 
Planned for an ISS flight demonstration
1011th G4SUW Presentation August 26, 2015
Space Radiation: Magnetic-based Forecasting (Mag4) 
• Marshall scientists and engineers developed an automated prediction 
system that downloads and analyzes magnetograms from the HMI 
(Helioseismic and Magnetic Imager) instrument on NASA SDO (Solar 
Dynamics Observatory), and then automatically converts the rate (or 
probability) of major flares (M- and X-class), Coronal Mass Ejections 
(CMEs), and Solar Energetic Particle Events
[Present cadence of new forecasts: 96 min; Vector magnetogram actual cadence: 12 min]
A magnetogram of an active region on the Sun
For each Active Region: 
The integral of the gradient 
along the neutral line is the 
free-energy proxy
When the transverse 
gradient of the vertical 
(or line-of-sight) magnetic 
field is large, there is more 
free-energy stored in the 
magnetic field
1111th G4SUW Presentation August 26, 2015
Mag4: A Comparison of Safe and Not Safe Days
June 26, 2013
C1, C1.5 flares
March 7, 2012
X5.4, X1.3, C1.6
CME 2684, 1825 km/sec,
Solar Energetic Proton Event reaches 
6530 ‘particle flux unit’ >10 MeV
1211th G4SUW Presentation August 26, 2015
Space Radiation: Modeling & Simulation
• Marshall scientists and engineers use Geant4 for the design, analysis, 
and development of
particle detector systems
exposures at accelerators and in-situ
dose estimates
shielding solutions 
• Marshall scientists and engineers collaborate
with experimental and theoretical and 
computational groups at Oak Ridge National                           
Laboratory, Berkeley’s Lawrence National                               
Laboratory, Brookhaven National 
Laboratory, Indiana University’s Cyclotron                                       
Facility, Japan’s HIMAC facility, and others for basic and applied 
nuclear modeling, simulation, and exposure and shielding studies   
1311th G4SUW Presentation August 26, 2015
Marshall managed HEDS’ Space 
Radiation Shielding Project (SRSP) 
and ETDP’s Advanced Avionics 
and Processor Systems (AAPS) 
Project. Under these two radiation 
projects:
• Marshall developed the first 
generation of multi-functional 
shielding materials
• Marshall managed  all 
accelerator-based testing of 
shielding materials
• Marshall managed the acquiring 
of basic nuclear-physics data 
needed for shielding and 
exposure risk assessment 
studies
• Marshall also developed a 
unique, sophisticated online 
simulation tools to reliably gauge 
the radiation effects on 
electronics (Crème-MC) Virtual Irradiation Capabilities of Crème-MC
Space Radiation: Modeling & Simulation
1411th G4SUW Presentation August 26, 2015
Space Radiation: Modeling & Simulation
●p1 ● p2
Δz Δz
Z-direction≈
Complex geometry and material composition -in the presence of 
known physical uncertainties- are expected to produce sizable 
errors in any radiation protection solution.
A 2-D illustration:
} }
15CFD RC, Nov. 7, 2014
Radiation-Smart Structures and Designs?
A B
C
D
E
A: Adaptive Structures
B: Sensory Structures
C: Controlled Structures
D: Active Structures
E: Intelligent Structures
1611th G4SUW Presentation August 26, 2015
Space Radiation: Radiation-Smart Structures and Designs
Restraint Layer
MMOD
Shielding
Bumper Spacer
Bumper Material
AO/TPS
Redundant Bladder Assemby
Inner Liner
radiation shielding will most likely focus on 
MMOD shielding materials and core 
Smart Materials:
Multi-functional
Smart Designs:
Optimized
1711th G4SUW Presentation August 26, 2015
Space Radiation: Built-In Protection (A New Paradigm)
-NASA in collaboration with other
federal agencies, FFRDC, academia,
and the private sector is embarking 
on a new and radical way in looking 
at the challenges and solutions of
space-radiation exposure; from the
‘grounds’ up
-Marshall is at the heart of this new
paradigm making
-Geant4 and G4SUW are critical to 
the success of this new paradigm, 
and space-radiation solutions
Thanks for helping to make this vision become a reality…and soon!


Radiation Transport and Space-Radiation Related Efforts at NASA's Marshall Space Center

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