Transcript IONMARSE Technical Progress Meeting

Implementation of Nuclear-Nuclear
Physics in the Geant4 Radiation
Transport Toolkit for
Interplanetary Space Missions
Pete Truscott & Fan Lei
QinetiQ Ltd, Farnborough, UK
Petteri Nieminen
ESTEC, Noordwijk, The Netherlands
Johannes Peter Wellisch
CERN, Geneva, Switzerland
2
Outline
• Background and requirements
• Geant4
• Total cross-section models implemented
• Abrasion and EM dissociation final-state models implemented
• Summary
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Background and Requirements
Species and energy range of source particles for
interplanetary env.
• GCR:
– Very wide range in species, with noticeable dips after
He and Fe
– Typical energy range of concern: 10’s MeV/nuc 100’s GeV/nuc, although mean energy is several
hundred MeV/nuc.
• Solar particle events 10’s MeV/nuc to ~1 GeV/nuc:
– Impulsive, short-term events associated with solar flares have greater fraction of heavy particles
– CMEs (Coronal mass ejection) produce gradual events that are proton-rich and last longer
4
Background and Requirements
Dose Equivalent - GCR
Dose - GCR
Mg, Al, Si Fe
3%
4%
C, O, Ne
9%
Other
7%
Proton
19%
Other
23%
Proton
59%
Alpha
18%
Alpha
17%
Fe
13%
Mg, Al, Si
15%
C, O, Ne
13%
Dose - SPE
Dose Equivalent - SPE
Other
3%
Other
10%
Proton
97%
Data from W Schimmerling, J W Wilson, F Cucinota, and M-H Y Kim, 1998.
Proton
90%
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Background and Requirements
• Spacecraft engineers for future manned missions will require access to radiation shielding models
like Geant4 to optimise design of spacecraft structure / habitat and mission profile
• Models have to be applicable to energy range / particle species of GCR & SPE
• Applicable target materials:
– Man-made / transported materials such as: metal alloys of Al, Ti, Fe, Mg, Be; plastics and composites;
fuels/oxidizers; deliberate shielding materials (polyethene, water); crew consumables/life-support
– Mars atmosphere
– Martian or Lunar soil / regolith (O, Si, Al, Fe, Mg, Ca), including composites with man-transported
materials to form solid radiation shields
Regime
Hadron-nucleon
or hadron-nuclear
Work on extending QGS to treat nuclearnuclear
Model
Application
Very detailed model  time
Parameterised
consuming
Parton-string (>5GeV)
Cascade (10MeV-10GeV)
QMD models
Cosmic ray
nuclei and
secondaries
Trapped protons
and secondaries
Pre-compound (2-100 MeV)
At the time could only treat
hadron-nuclear interactions
(Light-ion Binary Cascade
code released Dec 04)
Nuclear
de-excitation
Low-energy neutron
(thermal - 20 MeV)
Secondary neutrons, including
atmospheric/planetary albedo neutrons
Isotope production
Induced radioactive background
calculations
Evaporation (A>16)
Treatment for seondaries from cosmic
ray nuclei and trapped protons, esp.
important in calculation of single event
effects (microdosimetry)
Fermi break-up (A16)
Fission (A65)
Multi-fragmentation
Photo-evaporation (ENSDF)
Radioactive decay (ENSDF)
Induced and natural radioactive
backgrounds
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Geant4 Inelastic Cross-Sections
Total cross-section models based on parametric fits:
• proton-nuclear & neutron-nuclear interactions
• Tripathi et al’s general algorithm for nuclear-nuclear
• Others introduced in December
Final state models to determine exact
interaction process and secondary particle
production
• Binary Cascade
• Classical Cascade
• Pre-equilibrium
Total cross-section models allow rapid determination of
mean-free paths, but cannot determine momentum
change and secondary particle production
New Classes to Treat Total Cross-Sections for Nuclear-Nuclear
Interaction
• Tripathi’s empirical formula for light nuclear-nuclear interactions (where A4 for either projectile
and/or target) - G4TripathiLightCrossSection
• Class G4GeneralSpaceNNCrossSection automatically selects (depending upon
projectile-target system) from:
– G4TripathiCrossSection
Tripathi “Standard” (NASA TP-3621, 1997)
– G4TripathiLightCrossSection Tripathi “Light” (NASA TP-1999-209726)
– G4IonsShenCrossSection
Shen (Nucl Phys, A491, 1989)
– G4ProtonInelasticCrossSection & G4IonsProtonCrossSection
Wellisch (Phys Rev C51, No3, 1996)
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Comparison of implementation of Tripathi “light” model with MathCAD algorithm and experiment
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-Al
-Ta
p-
p-Li
G4WilsonAbrasionModel
• In principle the abrasion model from Wilson’s NUCFRG2 should provide advantages in speed over
microscopic simulation performed by cascade models or JQMD
– Interaction region determined from geometric arguments
– Nuclear density assumed constant
– Number of “participants” in the overlap region based on approximation for nucleon mean-free path and maximum chord-length
in the overlap region
– NASA model follows this with ablation process - excitation from excess surface-area and kinetic energy transferred to nucleons
• Can use standard Geant4 de-excitation models (evaporation, Fermi break-up, multi-fragmentation, and photoevaporation)
• Wilson Ablation model also included: uses NUCFRG2 algorithm for selecting which light nuclear fragments
emitted from excited pre-fragment, and G4 evaporation to determine kinematics and recoil
• Abraded nucleons from projected and target nucleus treated, as well as de-excitation of projectile and target
pre-fragments
10
12
C-C 1050 MeV/nuc
10.0
1.0
Fragment
He6
Li6
Li7
Li8
Be7
Be9
Be10
B10
B11
C10
0.1
C11
cross-section [mb]
100.0
Abrasion + evap
Abrasion + ablation
Experiment
NUCFRG2
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Abrasion + evap
Abrasion + ablation
Experiment
NUCFRG2
Fe-C 600 MeV/nuc
10.0
1.0
10.0
1.0
0.1
56
Fe-C 1570 MeV/nuc
S35
S36
S37
Cl34
Cl35
Cl36
Cl37
Cl38
Cl39
Fragment
Abrasion + evap
Abrasion + ablation
Experiment
NUCFRG2
100.0
10.0
Abrasion + evap
Abrasion + ablation
Experiment
NUCFRG2
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O-Cu 2100 MeV/nuc
1000.0
cross-section [mb]
1000.0
Ar36
Ar37
Ar38
Ar39
Ar40
Ar41
K39
Ca40
Ca41
Ca42
Ca43
Ca44
Ca45
Sc43
Sc44
Sc45
Sc46
Sc47
Sc48
Ti44
Ti45
Ti46
Ti47
Ti48
0.1
Fragment
100.0
10.0
1.0
Fragment
Be11
B10
B11
B12
B13
C10
C11
C12
C13
C14
N12
N13
N14
P Si Al Mg Na Ne
N15
Mn Cr V Ti Sc Ca K Ar Cl S
Fragment
O14
0.1
1.0
O15
cross-section [mb]
Abrasion + evap
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Abrasion + ablation
Experiment
NUCFRG2
Fe-C 600 MeV/nuc
100.0
K38
cross-section [mb]
100.0
56
cross-section [mb]
56
Comparison of the percentage of times the predicted cross-section for fragment production is within a factor of E of
the experimental value (for various projectile nuclei on carbon target).
Percentage of cross-sections with error < E
100%
80%
60%
40%
Abrasion + evap
Abrasion + ablation
Binary Cascade + evap
NUCFRG2
20%
0%
1
10
Factor error, E
•
•
Abrasion model is better at predicting nuclear fragment yield using ablation (75% of time
within factor-of-two)
Binary Cascade does worst at predicting nuclear fragment
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Comparison of the predicted secondary proton spectrum from abrasion and Binary Cascade models, and experiment
for 800MeV/nuc 20Ne on 20Ne (protons exiting at ~30o(left) and ~40o (right)
1.E-04
Abrasion + evap
Binary Cascade
Experiment
1.E-05
1.E-06
Omnidirectional fluence per
incident fluence [/MeV]
Omnidirectional fluence per
incident fluence [/MeV]
1.E-04
Abrasion + evap
Binary Cascade
Experiment
1.E-05
1.E-06
1.E-07
1.E-07
0
200
400
600
Energy [MeV]
•
14
800
1000
0
200
400
600
Energy [MeV]
800
Binary Cascade model performs better than Abrasion model when predicting secondary nucleon spectrum >200
MeV
1000
Nuclear EM Dissociation
• Liberation of nucleons or nuclear fragments as a result of electromagnetic field, rather than the
strong nuclear force
• Important for relativistic nuclear-nuclear interaction, e.g. for 3.7GeV/nucleon 28Si projectiles in Ag,
ED accounts for ~25% of the nuclear interaction events
• NASA model used in HZEFRG and NUCFRG2 predict ED events for 1st and 2nd moments of
electric field and cross-sections for giant dipole / quadrupole resonances
• The G4EMDissociation model is an implementation of the NUCFRG2 physics
• Applied for dissociation of protons and neutrons from both the projectile and target
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Comparison of predicted and experimental EM dissociation crosssections
Projectile
Mg-24
Si-28
O-16
Energy
[GeV/ nuc]
3.7
3.7
14.5
Product from EMD
Na-23 + p
Al-27 + p
Al-27 + p
G4EMDissociation
[mbarn]
124  2
107  1
216  2
200
N-15 + p
331  2
Experiment
[mbarn]
154  31
186  56
165  24†
128  33‡
293  39†
342  22*
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Summary
• New nuclear-nuclear models implemented in Geant4 for :
– Abrasion model to simulate macroscopic production of pre-fragments
– Version of Wilson’s ablation model
– EM dissociation model simulating production of protons/neutrons for highly relativistic collisions
– Improved / easier-to-use total interaction cross-section classes
• New models complement other nuclear-nuclear physics developments in Geant4
(G4BinaryLightIonReaction, JQMD, QGSM)
• Abrasion model provide more accurate prediction of nuclear fragment production
• Results for Geant4 EM dissociation model generally consistent - within 5-42% of experiment
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Backup slides
Comparison of G4EMDissociationCrossSection and HZEFRG1 predictions for EMD cross-section of 56Fe incident on a
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variety of targets.
1.0E+05
Cross-section [mbarn]
1.0E+04
1.0E+03
Carbon (G4EMD)
Nitrogen (G4EMD)
Aluminium (G4EMD)
Iron (G4EMD)
Tantalum (G4EMD)
Gold (G4EMD)
Carbon (HZEFRG1)
Nitrogen (HZEFRG1)
Aluminium (HZEFRG1)
Iron (HZEFRG1)
Tantalum (HZEFRG1)
Gold (HZEFRG1)
1.0E+02
1.0E+01
1.0E+00
1.0E+01
1.0E+02
1.0E+03
Energy [MeV/nuc]
1.0E+04
1.0E+05
1.0E+06