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Geant4 Microdosimetry for Aerospace Radiation EffectsPete Truscott, Fan Lei, Clive DyerQinetiQ Ltd, Farnborough

Bart Quaghebeur Ramon NartalloBIRA, Brussels Rhea Systems SA, Belgium

Geant4 Space Users Workshop, Pasadena, CA 6th-11th November 2006QinetiQ 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

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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

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• 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

Geant4 Radiation Transport Toolkit - The Vices

from the point of view of an engineer, the toolkit is at best challenging to learn

and at worst appears positively user-hostile!!

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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

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GEant4 Microdosimetry Analysis Tool - GEMATA 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

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Material Definition Commands

Predefined materials:

• 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

# 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

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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

Depleted regions non-depleted active orinactive regions

x

y

z

Contacts

# 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

# 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

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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 Rectangular Parallelepiped

'L' shape

'U' shape

# 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

# 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

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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 volumes is low

Primary ParticleGenerator

Uses G4GeneralParticleSource (GPS)

G4GRASPhysicsList & Messenger

# 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

# 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

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Emission Neutron Spectrum

1.00E-06

1.00E-05

1.00E-04

1.00E-03

0.00E+00 2.00E+05 4.00E+05 6.00E+05 8.00E+05 1.00E+06 1.20E+06

Energy (keV)

neu

tro

ns/

ch/e

ven

t

Biased x 10

Unbiased

PHS

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

0.00E+00 5.00E+04 1.00E+05 1.50E+05 2.00E+05 2.50E+05

Energy (keV)

Co

un

ts/c

h/e

ven

t

Biased x 10

Unbiased

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

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Analysis Manager• 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

# 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

# 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

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• 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

GEMAT Implementation in SPENVIS

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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

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GEMAT geometry for four-transistor cell, forming part of a 4Mbit SRAM

Pink-outlined regions indicate sensitive volumes (determined through device reverse engineering)

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1.E-18

1.E-17

1.E-16

1.E-15

0 10 20 30 40 50 60 70

Proton energy [MeV]

SE

U c

ross

sec

tio

n [

cm2 /b

it]

Experiment data from Poivey

G4 Classical Cascade modelpredictionG4 Binary Cascade modelprediction

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

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Hitachi HM628512 ALP-7 Data compared with simulation

Hitachi A

1E-16

1E-15

1E-14

1E-13

1E-12

0 50 100 150 200 250 300 350 400 450 500

Energy (MeV)

Indiana (3 MeV)

WNR 2005 >10 MeV

Triumf 2005 10-400 MeV

TSL 2005 (peak)

TSL 2005 (peak+tail)

Geant4 simulation

TRIUMF 2000 proton

NPL 2002

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Hitachi HM628512 ALP-7 Data compared with simulation

Hitachi A

1E-16

1E-15

1E-14

1E-13

1E-12

0 5 10 15 20 25 30 35 40 45 50

Energy (MeV)

Indiana (3 MeV)

WNR 2005 >10 MeV

Triumf 2005 10-400 MeV

TSL 2005 (peak)

TSL 2005 (peak+tail)

Geant4 simulation

TRIUMF 2000 proton

NPL 2002

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QDOS Aircraft Radiation Monitor

A

BC

D E

G+H F

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

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1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

0 10 20 30 40 50 60 70 80

Energy [MeV]

Dif

fere

nti

al P

H s

pec

tru

m [

/MeV

-neu

tro

n]

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 MeVGeant4 Prediction 20 MeV

Comparison of QDOS/TRIUMF Data (6 Dec 2004) with MULASSIS Predictions

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

0 10 20 30 40 50 60 70 80

Energy {MeV]

Co

un

ts [

/MeV

-neu

tro

n]

TRIUMF Run #1TRIUMF Run #2TRIUMF Run #4G4 Binary CascadeG4 Classical Cascade

180MeV

100MeV50MeV

TRIUMF 2004:Comparison of measured and Geant4-predicted energy deposition spectra in 300m silicon detector irradiated by TRIUMF neutron spectrum

Theodor Svedberg Laboratory 2004: Comparison of measured and Geant4-predicted energy deposition spectra in 300m silicon detector irradiated by 20, 90 and 180 MeV neutrons

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1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

0 10 20 30 40 50 60

Energy [MeV]

Co

un

ts [

/MeV

-neu

tro

n]

TSL2005 Run #5: 100 MeV at frontGeant4 Binary CascadeGeant4 Classical Cascade

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.

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1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

0 10 20 30 40 50 60

Energy [MeV]

Co

un

ts [

/MeV

-neu

tro

n]

TSL2005 Run #6: 50 MeV at 533cmTSL2005 Run#6: 50 MeV at 533cm (no scattering)Geant4 Binary CascadeGeant4 Classical Cascade

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

0 10 20 30 40 50 60

Energy [MeV]

Co

un

ts [

/MeV

-neu

tro

n]

TSL2005 Run #7: 20 MeV at 533cm

TSL2005 Run #7: 20 MeV at 533cm (no scattering)

Geant4 Classical Cascade

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

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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)

96cm 38cm 37cm 95cm 4cm 50cm

Ortec diodedetector

neutrondirection

88cm 30cm

Al box (3.2mm totalthickness) containingPCB + Cd

PCB

Al

4cm18cm 73cm

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0

0.2

0.4

0.6

0.8

1

0 100 200 300 400 500 600

Distance from neutron beam monitor [cm]

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 continuum, since peak-flux to total-flux ratio increases

Neutron flux emerging from each PCB is slightly higher than that entering

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1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

0 10 20 30 40 50 60

Energy [MeV]

Co

un

ts [

/MeV

-neu

tro

n]

TSL2005 Run #6: 50 MeV at 533cmTSL2005 Run#6: 50 MeV at 533cm (no scattering)Geant4 Binary CascadeGeant4 Classical Cascade

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

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1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 10 20 30 40 50 60 70 80

Energy [MeV]

Co

un

ts [

/MeV

-neu

tro

n]

TSL2004 180MeV [x1000]G4Binary Cascade 180MeV [x1000]G4 Classical Cascade 180MeV [x1000]TSL2005 100 MeV [x100]G4 Binary Cascade 100MeV [x100]G4 Classical Cascade 100MeV [x100]TSL2005 50 MeV [x10]G4 Binary Cascade 50MeV [x10]G4 Classical Cascade 50MeV [x10]TSL2005 20 MeVG4 Classical Cascade 20MeV

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

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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

0

2

4

6

8

10

12

14

16

0.01 0.1 1 10 100

Energy [MeV/amu]

Ele

ctro

nic

sto

pp

ing

po

wer

[M

eV-c

m2 /m

g]

SRIM 2003PASS (ICRU-73)G4 - Ziegler 1985 implementationG4 - SRIM 2000 implementationG4 - ICRU_49 implementationG4 (Std EM)

28Si in silicon

?

• 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

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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

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