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Geant4 Microdosimetry for Aerospace Radiation Effects

Geant4 Microdosimetry for Aerospace Radiation Effects. Pete Truscott, Fan Lei, Clive Dyer QinetiQ Ltd, Farnborough Bart Quaghebeur Ramon Nartallo BIRA, Brussels Rhea Systems SA, Belgium Geant4 Space Users Workshop, Pasadena, CA 6 th -11 th November 2006

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Geant4 Microdosimetry for Aerospace Radiation Effects

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  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, Belgium Geant4 Space Users Workshop, Pasadena, CA 6th-11th 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

  2. Geant4 Radiation Transport ToolkitThe 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

  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 documentation, it’s a long and steep learning-curve from the point of view of an engineer, the toolkit is at best challenging to learn and at worst appears positively user-hostile!!

  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/ sources to shielding properties of concrete and boronated polythenes to neutrons <20MeV

  5. GEant4 Microdosimetry Analysis Tool - GEMAT A Geant4-based application for microdosimetry analysis of microelectronics • Easy to use geometry builder • Handles volumes 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

  6. Material Definition Commands • There are 4 predefined materials • New material can be added by given its name, element composition and density # Materials definition # /geometry/material/list /geometry/material/deleteName Air # /geometry/material/add SiO2 Si-O2 2.650 /geometry/material/add BPSG Si100-O200-B5-P5 2.650 /geometry/material/list Predefined materials:

  7. Geometry Construction Commands • A layered geometry structure • Arbitrary number of layers of different materials • One layer is designated as the Contact Layer • Contact Volumes (CVs) can be added • One layer is designated as the Depleted Layer • Sensitive Volumes (SVs) can be added # Define layers # /geometry/layer/add 0 SiO2 1 0.5 um /geometry/layer/add 1 BPSG 2 0.3 um /geometry/layer/add 2 Silicon 3 0.2 um /geometry/layer/add 3 SiO2 4 0.025 um /geometry/layer/add 4 Silicon 5 0.25 um /geometry/layer/add 5 Silicon 6 4.0 um /geometry/layer/list

  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. # Contact and depletion Volumes /geometry/CV/add/box 3 0.45 0.50 0.78 0.22 Silicon 6 um /geometry/CV/add/box 3 -0.10 -0.50 0.78 0.22 Aluminium 6 um /geometry/CV/add/box 3 2.10 -0.69 0.20 0.44 Silicon 6 um /geometry/CV/list /geometry/DV/add/box 5 -1.70 0.66 0.20 0.44 0.0 Silicon 7 um /geometry/DV/add/lshape 5 -0.33 0.43 0.50 0.69 0.20 0.44 0.0 Silicon 7 um /geometry/DV/add/box 5 -0.33 -1.13 0.50 0.38 0.0 Silicon 7 um /geometry/DV/list

  9. 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 volumes is low Physics List G4GRASPhysicsList & Messenger Primary ParticleGenerator # Define the incident particle # (use a smaller incident surface than the default one) /gps/pos/halfx 0.010 mm /gps/pos/halfy 0.010 mm /gps/particle neutron /gps/ene/type Pow /gps/ene/min 10 MeV /gps/ene/max 500 MeV /gps/ene/alpha -1 /gps/direction 0 0 -1 Uses G4GeneralParticleSource (GPS)

  10. 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

  11. Quantities tallied: Fluence Pulse height spectrum (PHS) Path-length Applied to selected sensitive volumes (SVs) Coincidence analysis: Between up to 3 DVs Each volume can have its own threshold Built-in histogram capability Wide choice of binning scheme, inc. arbitrary Output in CSV format Analysis Manager # fluence analysis # /analysis/fluence/particle/add proton /analysis/fluence/energy/mode log /analysis/fluence/energy/min 10. MeV /analysis/fluence/energy/max 100. MeV /analysis/fluence/energy/nbin 10 /analysis/fluence/energy/list # # PHS analysis # change the binning scheme # /analysis/phs/energy/mode lin /analysis/phs/energy/min 0. MeV /analysis/phs/energy/max 1. MeV /analysis/phs/energy/nbin 20 /analysis/phs/energy/list # # Coincidence analysis # set the trigger thresholds for DVs # /analysis/coinc/thres/set 1 0.1 keV /analysis/coinc/thres/set 2 0.1 keV /analysis/coinc/thres/set 3 0.1 keV /analysis/coinc/thres/set 4 0.1 keV /analysis/coinc/thres/set 5 0.1 keV /analysis/coinc/thres/set 6 0.1 keV # /analysis/coinc/thres/list

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

  15. Proton SEU predictions for Samsung KM684002A 4Mbit SRAM The energy-deposition spectrum 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 cm2/bit • Measured cross-section based on TRIUMF results with and without Cd: 1.6x10-16 cm2/bit

  16. Hitachi HM628512 ALP-7 Data compared with simulation

  17. Hitachi HM628512 ALP-7 Data compared with simulation

  18. 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 X

  19. TRIUMF 2004: Comparison of measured and Geant4-predicted energy deposition spectra in 300m silicon detector irradiated by TRIUMF neutron spectrum Theodor Svedberg Laboratory 2004: Comparison of measured and Geant4-predicted energy deposition spectra in 300m silicon detector irradiated by 20, 90 and 180 MeV neutrons 180MeV 50MeV 100MeV

  20. Theodor Svedberg Laboratory 2005: Measured and Geant4-predicted energy deposition spectrum in QDOS detector under neutron irradiation at TSL by 100 MeV quasi-monoenergetic neutrons (spectrum right). The diode detector was located 9cm downstream from the beam monitor.

  21. Theodor Svedberg Laboratory 2005: At other energies, there’s a problem… Experimental spectrum (per incident neutron) appear to be factor of 3-10 lower than prediction

  22. 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

  23. Neutron flux emerging from each PCB is slightly higher than that entering Most of the scattering occurs in low-energy continuum, since peak-flux to total-flux ratio increases

  24. Re-normalised experimental neutron spectrum at 533cm is in much better agreement with prediction

  25. Theodor Svedberg Laboratory 2005 - Final composite graph after accounting for neutron scattering

  26. Ion-Electromagnetic Physics 28Si in silicon • 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 ? Need Comparison With Expt. • 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 M2EDUSA G4 + detailed device physics simulation

  27. Summary • 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 supportmicro-/nanodosimetry and device physics simulation efforts

  28. Backup Slides

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