Geant4 Microdosimetry for Aerospace Radiation Effects

Transcription

1 Geant4 Microdosimetry for Aerospace Radiation Effects Pete Truscott, Fan Lei, Clive Dyer QinetiQ Ltd, Farnborough Bart Quaghebeur Ramon Nartallo BIRA, Brussels Rhea Systems SA, Belgi Geant4 Space Users Workshop, Pasadena, CA 6 th -11 th November 2006 QinetiQ developments and research funded by ESA under contract 19103/05/NL/JD, and by the UK MOD under contract C/MAT/N03517 and C/MAT/N02503E 1

2 Geant4 Radiation Transport Toolkit The Virtues Comprehensive Monte Carlo simulation of all particles in 3D geometries Variety of physics models covering electromagnetic, hadronic (nuclear), decay processes with treatment over 1PeV to ~100eV (and to thermal energies for neutrons) Developed initially for the HEP community (LHC at CERN, BarBar at SLAC and KEK) with contributions from 100 scientists from 40 institutes World-wide This toolkit continues to be supported through HEP, medical physics, space, etc communities as applications and requirements grow - new physics, new tools, new validations Implementation in C++ - aids enhancement of code through class inheritance 2

3 Geant4 Radiation Transport Toolkit - The Vices It is a toolkit Geant4 philosophy considers it the responsibility of the user to write the application and the develop post-processing tools Need for applications like MULASSIS, SSAT, GRAS Although there is extensive docentation, it s a long and steep learningcurve from the point of view of an engineer, the toolkit is at best challenging to learn and at worst appears positively user-hostile!! 3

4 Multi-Layered Shielding Simulation Software (MULASSIS) Geant4 application to allow radiation analysis for 1D geometries (slab & sphere) Provide Shieldose-type information with the physics of G4 SPENVIS or standalone versions Simple specification of geometry (comprising any materials), source particle, physics, and analysis: TID, DD, fluence, energy-deposition spectra Graded shielding analysis for electron/γ sources to shielding properties of concrete and boronated polythenes to neutrons <20MeV 4

5 GEant4 Microdosimetry Analysis Tool - GEMAT A Geant4-based application for microdosimetry analysis of microelectronics Easy to use geometry builder Handles voles more complex than regular parallelepipeds GRAS-based physics list Making use of the full G4 physics capability Built-in analysis modes PHS: SEU rates calculated based on experimental ion data Path-length: used with environment h-ion LET data Analysis of coincidence events SPENVIS-based to allow wider usage without having to download Geant4 5

6 Material Definition Commands There are 4 predefined materials New material can be added by given its name, element composition and density Predefined materials: Materials Materials definition definition /geometry/material/list /geometry/material/list /geometry/material/deletename /geometry/material/deletename Air Air /geometry/material/add /geometry/material/add SiO2 SiO2 Si-O2 Si-O /geometry/material/add /geometry/material/add BPSG BPSG Si100-O200-B5-P5 Si100-O200-B5-P /geometry/material/list /geometry/material/list 6

7 Geometry Construction Commands A layered geometry structure Arbitrary nber of layers of different materials One layer is designated as the Contact Layer Contact Voles (CVs) can be added One layer is designated as the Depleted Layer Sensitive Voles (SVs) can be added x z Contacts y Define Define layers layers /geometry/layer/add /geometry/layer/add 0 0 SiO2 SiO /geometry/layer/add /geometry/layer/add 1 1 BPSG BPSG /geometry/layer/add /geometry/layer/add /geometry/layer/add /geometry/layer/add 3 3 SiO2 SiO /geometry/layer/add /geometry/layer/add /geometry/layer/add /geometry/layer/add /geometry/layer/list /geometry/layer/list Depleted regions non-depleted active or inactive regions 7

8 CV/DV Shapes Basic shapes Cylinder: 2 parameters Box: 2 parameters L-shape: 4 parameters U-shape: 4 parameters All can be tapered at top/bottom Position (x,y) in the layer Material & Visualisation Attrib. Cylinder 'L' shape Rectangular Parallelepiped Contact Contact and and depletion depletion Voles Voles /geometry/cv/add/box /geometry/cv/add/box /geometry/cv/add/box /geometry/cv/add/box Alini Alini 6 6 /geometry/cv/add/box /geometry/cv/add/box /geometry/cv/list /geometry/cv/list 'U' shape 8 /geometry/dv/add/box /geometry/dv/add/box /geometry/dv/add/lshape /geometry/dv/add/lshape /geometry/dv/add/box /geometry/dv/add/box /geometry/dv/list /geometry/dv/list

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10 Physics List G4LowEnergyEM G4HPNeutron G4Binary/G4Bertini G4BinaryLightIon G4Abrasion/G4Ablation G4RadioactiveDecay Layer dependent cut-offs Bias the cross-sections not currently in GEMAT - important as probabilities for interactions in small voles is low G4GRASPhysicsList & Messenger 10 Primary Particle Generator Uses G4GeneralParticleSource (GPS) Define Define the the incident incident particle particle (use (use a a smaller smaller incident incident surface surface than than the the default default one) one) /gps/pos/halfx /gps/pos/halfx mm mm /gps/pos/halfy /gps/pos/halfy mm mm /gps/particle /gps/particle neutron neutron /gps/ene/type /gps/ene/type Pow Pow /gps/ene/min /gps/ene/min MeV MeV /gps/ene/max /gps/ene/max MeV MeV /gps/ene/alpha /gps/ene/alpha -1-1 /gps/direction /gps/direction

11 Geant4 cross-section biasing results for 1GeV protons normally incident upon 1mm silicon Variance reduction implemented in a wrapper-class process 2hrs CPU time simulation for biased and unbiased runs Emission Neutron Spectr PHS 1.00E E E-01 Biased x 10 neutrons/ch/event 1.00E E-05 Biased x 10 Unbiased Counts/ch/event 1.00E E E E-05 Unbiased 1.00E E E E E E E E E+06 Energy (kev) 1.00E E E E E E E+05 Energy (kev) 11

12 12 Analysis Manager Quantities tallied: Fluence Pulse height spectr (PHS) Path-length Applied to selected sensitive voles (SVs) Coincidence analysis: Between up to 3 DVs Each vole can have its own threshold Built-in histogram capability Wide choice of binning scheme, inc. arbitrary Output in CSV format fluence fluence analysis analysis /analysis/fluence/particle/add /analysis/fluence/particle/add proton proton /analysis/fluence/energy/mode /analysis/fluence/energy/mode log log /analysis/fluence/energy/min /analysis/fluence/energy/min MeV MeV /analysis/fluence/energy/max /analysis/fluence/energy/max MeV MeV /analysis/fluence/energy/nbin /analysis/fluence/energy/nbin /analysis/fluence/energy/list /analysis/fluence/energy/list PHS PHS analysis analysis change change the the binning binning scheme scheme /analysis/phs/energy/mode /analysis/phs/energy/mode lin lin /analysis/phs/energy/min /analysis/phs/energy/min MeV MeV /analysis/phs/energy/max /analysis/phs/energy/max MeV MeV /analysis/phs/energy/nbin /analysis/phs/energy/nbin /analysis/phs/energy/list /analysis/phs/energy/list Coincidence Coincidence analysis analysis set set the the trigger trigger thresholds thresholds for for DVs DVs /analysis/coinc/thres/set /analysis/coinc/thres/set kev kev /analysis/coinc/thres/set /analysis/coinc/thres/set kev kev /analysis/coinc/thres/set /analysis/coinc/thres/set kev kev /analysis/coinc/thres/set /analysis/coinc/thres/set kev kev /analysis/coinc/thres/set /analysis/coinc/thres/set kev kev /analysis/coinc/thres/set /analysis/coinc/thres/set kev kev /analysis/coinc/thres/list /analysis/coinc/thres/list

13 GEMAT Implementation in SPENVIS Implementation into SPENVIS is currently being completed at BIRA Use other parts of SPENVIS to generate incident particle spectra Like MULASSIS, web-page access to control generation of Geant4 macro file: Can be executed at SPENVIS server - no need to download Geant4 to your local computer Lazy-Boy approach: download macro and execute with local copy of G4+GEMAT application 13

14 An application Example: 4 Mbit SRAMs A large quantity of beam test data available, from heavy Ion to thermal neutrons Good knowledge of the device geometry Two types of simulations using Detailed geometry at cell level An array of simple cells 14

15 GEMAT geometry for four-transistor cell, forming part of a 4Mbit SRAM 15 Pink-outlined regions indicate sensitive voles (determined through device reverse engineering)

16 Proton SEU predictions for Samsung KM684002A 4Mbit SRAM 1.E-15 SEU cross section [cm 2 /bit] 1.E-16 1.E-17 Experiment data from Poivey G4 Classical Cascade model prediction G4 Binary Cascade model di ti 1.E Proton energy [MeV] The energy-deposition spectr from events in SVs integrated over a Weibull fit to LET data from heavy-ion tests Predicted thermal neutron cross-section (from pre-metal BPSG) 9.3x10-17 cm 2 /bit Measured cross-section based on TRIUMF results with and without Cd: 1.6x10-16 cm 2 /bit 16

17 Hitachi HM ALP-7 Data compared with simulation Hitachi A 1E-12 1E-13 1E-14 1E-15 1E-16 Indiana (3 MeV) WNR 2005 >10 MeV Trif MeV TSL 2005 (peak) TSL 2005 (peak+tail) Geant4 simulation TRIUMF 2000 proton NPL Energy (MeV) 17

18 Hitachi HM ALP-7 Data compared with simulation Hitachi A 1E-12 1E-13 1E-14 1E-15 1E-16 Indiana (3 MeV) WNR 2005 >10 MeV Trif MeV TSL 2005 (peak) TSL 2005 (peak+tail) Geant4 simulation TRIUMF 2000 proton NPL Energy (MeV) 18

19 QDOS Aircraft Radiation Monitor Left & lower left: Hand-carried, battery-operated unit comprising detector (A), PDA for user-interface (B) and recharging equipment (D-H) Below: QDOS detector board (X) and MCA (Y) mounted on trolley prior to lowering into TRIUMF neutron beam Y G+H F C B X 19 D E A

20 TRIUMF 2004: Comparison of measured and Geant4- predicted energy deposition spectra in 300µm silicon detector irradiated by TRIUMF neutron spectr Counts [/MeV-neutron] 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 Comparison of QDOS/TRIUMF Data (6 Dec 2004) with MULASSIS Predictions TRIUMF Run 1 TRIUMF Run 2 TRIUMF Run 4 G4 Binary Cascade G4 Classical Cascade 1.E-08 Differential PH spectr [/MeV-neutron] 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 50MeV 100MeV 1.E-09 TSL Experiment 180MeV (x100) G4 Binary Cascade prediction 180MeV (x100) G4 Classical Cascade prediction 180MeV (x100) TSL Experiment 90 MeV (x10) G4 Binary Cascade prediction 90MeV (x10) G4 Classical Cascade prediction 90MeV (x10) TSL Experiment 20 MeV Geant4 Prediction 20 MeV Energy {MeV] 180MeV Theodor Svedberg Laboratory 2004: Comparison of measured and Geant4-predicted energy deposition spectra in 300µm silicon detector irradiated by 20, 90 and 180 MeV neutrons 20 1.E Energy [MeV]

21 Theodor Svedberg Laboratory 2005: Measured and Geant4-predicted energy deposition spectr in QDOS detector under neutron irradiation at TSL by 100 MeV quasi-monoenergetic neutrons (spectr right). The diode detector was located 9cm downstream from the beam monitor. 1.E-03 1.E-04 TSL2005 Run 5: 100 MeV at front Geant4 Binary Cascade Geant4 Classical Cascade Counts [/MeV-neutron] 1.E-05 1.E-06 1.E-07 1.E-08 1.E Energy [MeV] 21

22 1.E-03 Theodor Svedberg Laboratory 2005: At other energies, there s a problem Experimental spectr (per incident neutron) appear to be factor of 3-10 lower than prediction Counts [/MeV-neutron] 1.E-04 1.E-05 1.E-06 1.E-07 TSL2005 Run 6: 50 MeV at 533cm TSL2005 Run6: 50 MeV at 533cm (no scattering) Geant4 Binary Cascade Geant4 Classical Cascade 1.E-08 Counts [/MeV-neutron] 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 1.E Energy [MeV] TSL2005 Run 7: 20 MeV at 533cm TSL2005 Run 7: 20 MeV at 533cm (no scattering) Geant4 Classical Cascade 22 1.E Energy [MeV]

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24 In-Beam Neutron Scattering In several cases QDOS was located relatively far downstream of the neutron source Whilst beam divergence from the Li-foil (3m upstream of the monitor) had been accounted for, loss of neutrons through scattering within the experiments hadn t Adapted the MULASSIS code for long-thin geometries instead of short-fat geometries to simulate neutron interactions in PCBs, ICs, Cd foil, Al enclosures Beam-line exit Neutron beam monitor PCBs (red) Cd plate (blue) PCBs (red) Al box (3.2mm total thickness) containing PCB + Cd Al Ortec diode detector PCB neutron direction 96cm 38cm 37cm 95cm 4cm 18cm 73cm 88cm 30cm 50cm 4cm 24

25 1 0.8 Neutron flux emerging from each PCB is slightly higher than that entering Fraction of neutron flux >0.1MeV (100MeV) Fraction of neutron flux >0.1MeV (24MeV) Peak flux / total flux (100MeV) Peak flux / total flux (24MeV) Most of the scattering occurs in low-energy continu, since peak-flux to total-flux ratio increases Distance from neutron beam monitor [cm] 25

26 Re-normalised experimental neutron spectr at 533cm is in much better agreement with prediction 1.E-03 Counts [/MeV-neutron] 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 TSL2005 Run 6: 50 MeV at 533cm TSL2005 Run6: 50 MeV at 533cm (no scattering) Geant4 Binary Cascade Geant4 Classical Cascade 1.E Energy [MeV] 26

27 Theodor Svedberg Laboratory Final composite graph after accounting for neutron scattering Counts [/MeV-neutron] 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 TSL MeV [x1000] G4Binary Cascade 180MeV [x1000] G4 Classical Cascade 180MeV [x1000] TSL MeV [x100] G4 Binary Cascade 100MeV [x100] G4 Classical Cascade 100MeV [x100] TSL MeV [x10] G4 Binary Cascade 50MeV [x10] G4 Classical Cascade 50MeV [x10] TSL MeV G4 Classical Cascade 20MeV 1.E-07 1.E Energy [MeV] 27

28 Ion-Electromagnetic Physics Stopping power models G4 Std EM G4 Low-E models (Ziegler 1985 & ICRU-49) Work of Sigmund et al, including ICRU-73 (2006) Ziegler 2003 Electronic stopping power [MeV-cm 2 /mg] ? SRIM 2003 PASS (ICRU-73) G4 - Ziegler 1985 implementation G4 - SRIM 2000 implementation G4 - ICRU_49 implementation G4 (Std EM) 28 Si in silicon Energy [MeV/amu] Physics of REACT code for charge collection being implemented into GEMAT under ESA REAT-MS project Expected to make use of a range of detailed ion-track physics models for spatial distribution of charge developed under UK MOD contract e.g. Kobetich & Katz (1968, 1969), Zhang, Dunn & Katz (1985), Cucinotta, Katz et al (1995), Waligórski, Hamm & Katz (1986) Previously used in conjunction with M 2 EDUSA G4 + detailed device physics simulation 28

29 Smary Geant4 is playing an important role in QinetiQ s work on understanding radiation effects on semiconductor devices and detectors ESA-sponsored work has led to development of an easier-to-use engineering tool GEMAT, currently being implemented at SPENVIS It is vitally important that we pay attention to the detailed physical models (kinematics of highly-ionising secondaries): ion-em physics energetic proton/neutron-nuclear interactions and nuclear-nuclear low-energy neutrons - down to thermal energies for B-neutron interactions Hopeful of new 4½-year contract with MOD - will support micro-/nanodosimetry and device physics simulation efforts 29

30 30 Backup Slides