IONMARSE Technical Progress Meeting - Geant4 - CERN

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IONMARSE Technical Progress Meeting - Geant4 - CERN Powered By Docstoc
					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
                                                                      3


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 - GCR                                Dose Equivalent - GCR



                                Other
                Mg, Al, Si Fe    7%
                                                                    Other                            Proton
                   4%      3%                                       23%                               19%
          C, O, Ne
             9%



                                                                                                              Alpha
                                                     Proton    Fe
             Alpha                                                                                            17%
                                                      59%     13%
             18%
                                                                       Mg, Al, Si                C, O, Ne
                                                                         15%                       13%

                                   Dose - SPE                               Dose Equivalent - SPE


                                    Other                                   Other
                                     3%                                     10%




                                            Proton                                            Proton
                                             97%                                               90%




Data from W Schimmerling, J W Wilson, F Cucinota, and M-H Y Kim,
1998.
                                                                             5


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
                                  Work on extending QGS to                                        6
           Regime                 treat nuclear-nuclear
                                      Model                    Application

        Hadron-nucleon     Parameterised                              Very detailed
       or hadron-nuclear
                           Parton-string (>5GeV)    Cosmic ray
                                                                      model  time
                                                    nuclei and        consuming
                           Cascade (10MeV-10GeV)       secondaries            Trapped protons
                                                                              and secondaries
                           QMD models

                           Pre-compound (2-100 MeV)

At the time could          Low-energy neutron          Secondary neutrons, including
only treat hadron-         (thermal - 20 MeV)          atmospheric/planetary albedo neutrons

nuclear interactions       Isotope production          Induced radioactive background
                                                       calculations
(Light-ion Binary          Evaporation (A>16)          Treatment for seondaries from cosmic
           Nuclear
Cascade code
         de-excitation                                 ray nuclei and trapped protons, esp.
                           Fermi break-up (A16)       important in calculation of single event
released Dec 04)
                           Fission (A65)              effects ( microdosimetry)

                           Multi-fragmentation

                           Photo-evaporation (ENSDF)
                                                       Induced and natural radioactive
                           Radioactive decay (ENSDF)   backgrounds
                                                                                7


 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
                                                                           8
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)
Comparison of implementation of Tripathi “light” model with MathCAD algorithm and
                                   experiment                                   9




  -Al                                     -Ta




   p-                                      p-Li
G4WilsonAbrasionModel                                                                      10



• 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 photo-evaporation)
• 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
                                              12
                                               C-C 1050 MeV/nuc               Abrasion + evap       11

                                                                              Abrasion + ablation
                100.0                                                         Experiment
                                                                              NUCFRG2
cross-section [mb]



                     10.0


                      1.0


                      0.1




                                                                                  Li7

                                                                                        Li6
                                                   B10




                                                                            Li8
                                                                Be9
                            C11

                                  C10

                                        B11




                                                         Be10




                                                                      Be7




                                                                                              He6
                                                            Fragment
                                                                                                                                                                                                                           56
                                                         56                                                      Abrasion + evap                                                                                                Fe-C 600 MeV/nuc                                       Abrasion + evap
                                                              Fe-C 600 MeV/nuc
                                                                                                                 Abrasion + ablation                                                                                                                                                   Abrasion + ablation
                                                                                                                                                                                                                                                                                                    12
                100.0                                                                                            Experiment                                          100.0                                                                                                             Experiment
                                                                                                                 NUCFRG2                                                                                                                                                               NUCFRG2




                                                                                                                                                     cross-section [mb]
cross-section [mb]




                     10.0                                                                                                                                                         10.0



                      1.0                                                                                                                                                          1.0


                      0.1                                                                                                                                                          0.1
                                    Ti47
                                           Ti46




                                                                                                          Ca45
                                                                                                                  Ca44



                                                                                                                                       Ca41
                                                                                                                                              Ca40
                                                  Ti45


                                                                Sc48
                                                                       Sc47
                                                                              Sc46



                                                                                                   Sc43
                             Ti48




                                                         Ti44




                                                                                                                                Ca42
                                                                                     Sc45
                                                                                            Sc44




                                                                                                                         Ca43




                                                                                                                                                                                                 K38


                                                                                                                                                                                                                  Ar40


                                                                                                                                                                                                                                  Ar38
                                                                                                                                                                                                                                         Ar37
                                                                                                                                                                                                                                                Ar36




                                                                                                                                                                                                                                                                                                                S36
                                                                                                                                                                                                                                                         Cl39


                                                                                                                                                                                                                                                                          Cl37



                                                                                                                                                                                                                                                                                                  Cl34
                                                                                                                                                                                          K39


                                                                                                                                                                                                         Ar41


                                                                                                                                                                                                                           Ar39




                                                                                                                                                                                                                                                                                                          S37


                                                                                                                                                                                                                                                                                                                       S35
                                                                                                                                                                                                                                                                  Cl38


                                                                                                                                                                                                                                                                                  Cl36
                                                                                                                                                                                                                                                                                          Cl35
                                                                              Fragment                                                                                                                                                          Fragment

                                                         56                                                  Abrasion + evap                                                                                               16                                                          Abrasion + evap
                                                              Fe-C 1570 MeV/nuc                                                                                                                                               O-Cu 2100 MeV/nuc
                                                                                                             Abrasion + ablation                                                                                                                                                       Abrasion + ablation
                1000.0                                                                                       Experiment                                                                                                                                                                Experiment
                                                                                                                                                                          1000.0
                                                                                                             NUCFRG2                                                                                                                                                                   NUCFRG2




                                                                                                                                                             cross-section [mb]
cross-section [mb]




                                                                                                                                                                                  100.0
                     100.0

                                                                                                                                                                                   10.0

                      10.0
                                                                                                                                                                                    1.0


                       1.0                                                                                                                                                          0.1
                                                                                                                                                                                           O15
                                                                                                                                                                                                   O14


                                                                                                                                                                                                                     N14
                                                                                                                                                                                                                                N13


                                                                                                                                                                                                                                            C14
                                                                                                                                                                                                                                                       C13


                                                                                                                                                                                                                                                                         C11
                                                                                                                                                                                                                                                                                 C10
                                                                                                                                                                                                            N15




                                                                                                                                                                                                                                      N12




                                                                                                                                                                                                                                                                C12




                                                                                                                                                                                                                                                                                                 B12
                                                                                                                                                                                                                                                                                         B13


                                                                                                                                                                                                                                                                                                         B11
                                                                                                                                                                                                                                                                                                                B10
                                                                                                                                                                                                                                                                                                                      Be11
                              Mn Cr V Ti Sc Ca K Ar Cl S                                                  P Si Al Mg Na Ne
                                                Fragment                                                                                                                                                                                        Fragment
    Comparison of the percentage of times the predicted cross-section for                                          13
    fragment production is within a factor of E of the experimental value (for
    various projectile nuclei on carbon target).
                                                         100%
           Percentage of cross-sections with error < E



                                                         80%




                                                         60%




                                                         40%


                                                                                      Abrasion + evap
                                                         20%                          Abrasion + ablation
                                                                                      Binary Cascade + evap
                                                                                      NUCFRG2

                                                          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
                                  Comparison of the predicted secondary proton spectrum from abrasion and                                                         14
                                  Binary Cascade models, and experiment for 800MeV/nuc 20Ne on 20Ne
                                  (protons exiting at ~30o(left) and ~40o (right)
                              1.E-04                                                                               1.E-04
                                                                Abrasion + evap                                                                      Abrasion + evap




                                                                                     Omnidirectional fluence per
Omnidirectional fluence per




                                                                Binary Cascade                                                                       Binary Cascade




                                                                                      incident fluence [/MeV]
 incident fluence [/MeV]




                                                                Experiment                                                                           Experiment
                              1.E-05                                                                               1.E-05




                              1.E-06                                                                               1.E-06




                                                                                                                   1.E-07
                              1.E-07
                                       0   200   400      600       800       1000                                          0   200   400      600       800       1000
                                                 Energy [MeV]                                                                         Energy [MeV]




                              •    Binary Cascade model performs better than Abrasion model when
                                   predicting secondary nucleon spectrum >200 MeV
                                                                     15

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
                                                                                16
Comparison of predicted and experimental EM
dissociation cross-sections

   Projectile     Energy     Product from EMD   G4EMDissociation   Experiment
                [GeV/ nuc]                          [mbarn]          [mbarn]
    Mg-24           3.7         Na-23 + p            124  2        154  31
    Si-28           3.7         Al-27 + p            107  1        186  56
                   14.5         Al-27 + p            216  2        165  24†
                                                                    128  33‡
     O-16          200           N-15 + p           331  2         293  39†
                                                                    342  22*
                                                                           17


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
                18




Backup slides
Comparison of G4EMDissociationCrossSection and HZEFRG1 predictions for 19
        EMD cross-section of 56Fe incident on a variety of targets.
                          1.0E+05

                                         Carbon (G4EMD)
                                         Nitrogen (G4EMD)
                                         Aluminium (G4EMD)
                                         Iron (G4EMD)
                          1.0E+04        Tantalum (G4EMD)
                                         Gold (G4EMD)
  Cross-section [mbarn]




                                         Carbon (HZEFRG1)
                                         Nitrogen (HZEFRG1)
                                         Aluminium (HZEFRG1)
                          1.0E+03        Iron (HZEFRG1)
                                         Tantalum (HZEFRG1)
                                         Gold (HZEFRG1)



                          1.0E+02




                          1.0E+01
                               1.0E+00       1.0E+01           1.0E+02       1.0E+03        1.0E+04   1.0E+05   1.0E+06
                                                                         Energy [MeV/nuc]

				
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posted:12/25/2012
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