Dr. Scott R. MessengerSFA, Inc.
SPENVIS & GEANT4 workshop Faculty Club
Leuven, Belgium3 - 7 October 2005
Displacement Damage Dose Approach For Determining Solar Cell Degradation In
Space With Spenvis Implementation
• Introduction• Space Solar Cell Degradation Calculations
– NASA JPL Equivalent Fluence Method– NRL Displacement Damage Dose (Dd) Method
• Nonionizing Energy Loss (NIEL)
– Comparisons
• SPENVIS Implementation– MULASSIS is the key
• Notes• Future Work
Outline
S. Messenger, SPENVIS Workshop 2005
• Omnidirectional, isotropic, energy spectrum in space
• Unidirectional, normally incident, monoenergetic irradiation of bare solar cells on the ground
p+
COVERGLASS
SUBSTRATE
ACTIVE CELL
PANEL
p+
e-
e-
e-
e-
e-
p+
p+
p+
p+
p+
p+
COVERGLASS
SUBSTRATE
ACTIVE CELL
PANEL
p+
e-
e-
e-
e-
e-
p+
p+
p+
p+
p+
COVERGLASS
SUBSTRATE
ACTIVE CELL
PANEL
p+
e-
e-
e-
e-
e-
p+
p+
p+
p+
p+
protons
electrons
The Problem
S. Messenger, SPENVIS Workshop 2005
*Planar, slab geometry
Pmax Degradation Curves for GaAs/Ge Solar Cells (JPL, 1991)
108
109
1010
1011
1012
1013
1014
1015
1016
1017
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0N
orm
aliz
ed M
axim
um
Po
wer 1 Sun, AMO
GaAs/Ge
Particle Fluence (cm-2
)
Protons
Electrons0.6 MeV1 MeV2.4 MeV12 MeV
9.5 MeV3 MeV1 MeV0.5 MeV0.3 MeV0.2 MeV0.1 MeV0.05 MeV
25oC
S. Messenger, SPENVIS Workshop 2005
• Equivalent Fluence Method – created by NASA Jet Propulsion Laboratory (JPL)– Can be implemented through available FORTAN programs
– Is included in the SPENVIS web-suite (and others)
– Has widespread application and over 30 years of heritage
• Displacement Damage Dose Method (Dd) – created by the US Naval Research Laboratory (NRL)– Does not have widespread application due to lack of distributed computational
tool
• Solar Array Verification and Analysis Tool (SAVANT) is available but only in beta-version (unfunded at present)
• This paper shows how the SPENVIS web-suite can be used to implement the Dd method
The Solution
S. Messenger, SPENVIS Workshop 2005
JPL and NRL Methods
•NASA Jet Propulsion Laboratory (Pasadena, CA)
–Reduces mission space radiation effects to an equivalent 1 MeV electron fluence
–Read EOL power from measured 1 MeV electron curve
•US Naval Research Laboratory (Washington, DC)
–Calculate displacement damage dose, Dd, for mission
–Read EOL power from measured characteristic curve
S. Messenger, SPENVIS Workshop 2005
JPL Method (Equivalent Fluence Method)
•Summarized in two publications (developed in 1980’s)
–Solar Cell Radiation Handbook, JPL Publication 82-69 (1982)
–GaAs Solar Cell Radiation Handbook, JPL Publication 96-9 (1996)
•Utilizes the concept of relative damage coefficients (RDC’s)
•Reduces all damage to a 1 MeV electron equivalent fluence and uses 1 MeV electron data to get the EOL result
•Several computer programs (FORTRAN) are available:
–EQFLUX (Si), EQGAFLUX (GaAs), and multijunction (MJ) cell
–Other programs (e.g. SPENVIS and Space Radiation) implement JPL method
S. Messenger, SPENVIS Workshop 2005
Measure PV Degradation Curves (~4 electron and
~8 proton energies)
Determine Damage Coefficients for Uncovered Cells
Calculate Damage Coefficients for Isotropic Particles w/ Coverglasses of Varied
Thickness
Read Off EOL Values
Determine Incident Particle Spectrum (e.g. AP8)
JPL Equivalent Fluence Method
1 MeV Electron Degradation Curve
Calculate Equivalent 1 MeV Electron Fluence for Orbit (EQGAFLUX)
S. Messenger, SPENVIS Workshop 2005
Electron Damage Coefficients
Proton Damage Coefficients
Electron and ProtonFluence Data (GaAs/Ge, 1991)
JPL Equivalent Fluence Method
10-1 100 101 102
Electron Energy (MeV)
10-3
10-2
10-1
100
101
102
Rel
ativ
e P
max
Dam
age
Co
effi
cien
t
0 mil1 mil3 mil6 mil12 mil20 mil30 mil60 mil
Coverglass Thickness
*Relative to 1 MeV normalincidence data, w/o coverglass
Normal incidenceno coverglass
10-2 10-1 100 101 102
Proton Energy (MeV)
10-2
10-1
100
101
102
Rel
ativ
e P
max
Dam
age
Co
effi
cien
t0 mil1 mil3 mil6 mil12 mil20 mil30 mil60 mil
Coverglass Thickness
*Relative to 10 MeV proton normalincidence data, w/o coverglass
Normal incidenceno coverglass
108
109
1010
1011
1012
1013
1014
1015
1016
1017
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
No
rmal
ized
Max
imu
m P
ow
er 1 Sun, AMOGaAs/Ge
Particle Fluence (cm-2
)
Protons
Electrons0.6 MeV1 MeV2.4 MeV12 MeV
9.5 MeV3 MeV1 MeV0.5 MeV0.3 MeV0.2 MeV0.1 MeV0.05 MeV
25oC
75% BOL
S. Messenger, SPENVIS Workshop 2005
Equivalent 1 MeV Electron Fluence
2/
0
0 dsin2)0,E(RDC4
1t)RDC(E,
ppp
pppeee
e
eeelectronMeV 1 t)dE,(ERDC
dE
)(EdCt)dE,(ERDC
dE
)(Ed
cos
t)E(RR)t,,E(E 1
0
where the energy loss is determined from
R(E) is the range
(for electrons*)
where the RDCs for a coverglass thickness t is:
*for protons, another term is included to account for end-of-track effects
S. Messenger, SPENVIS Workshop 2005
Initial Omnidirectional Spectrum
Equivalent 1 MeV Electron Fluence
Proton Damage Coefficients
1 MeV Electron Pmax Degradation
10-1 100 101 102 103
Proton Energy (MeV)
5000 km, circular, 600 orbit (1 year duration)
107
108
109
1010
1011
1012
1013
1014
Flu
ence
(cm
2 MeV
)-1
10-2 10-1 100 101 102
Proton Energy (MeV)
10-2
10-1
100
101
Rel
ativ
e P
max
Dam
age
Coe
ffic
ien
t
0 mil1 mil3 mil6 mil12 mil20 mil30 mil60 mil
Coverglass
*Relative to 10 MeV normalincidence data, w/o
Thickness
coverglass, based on Pmax
1014 1015 1016 1017
1 MeV Electron Fluence (e-/cm2)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Nor
mal
ized
Pm
ax D
egra
dat
ion
GaAs/Ge (JPL, 1990)
1 Sun, AM0, 25oC
JPL Equivalent Fluence Method
0 10 20 30 40 50 60 70 80SiO2 Coverglass Thickness (mil)
1014
1015
1016
1 M
eV E
lect
ron
Flu
ence
(e- /c
m2 )
GaAs
5000 km, circular, 60o orbit (1 year duration)
JPL Model Pros/Cons
• Pros:– Heritage (developed in the 1980s)– Widely available and already incorporated into many space
radiation suites (SPENVIS, Space RadiationTM, etc.)
• Cons:– Much ground test data needed ($$)– Requires 1 MeV electron AND 10 MeV proton data– Currently available for Si (1982), GaAs/Ge (1996), MJ (1999)– Program not particularly user friendly (FORTRAN)
– Several flags need to be set– Entire calculation is technology specific (every design change
needs requalification, $$)
S. Messenger, SPENVIS Workshop 2005
NRL Method (Displacement Damage Dose, Dd)
•Summarized in:–Progress in PV: Research and Applications 9, 103-121 (2001)–Appl. Phys. Lett. 71, 832 (1997)–IEEE Trans. Nucl. Sci. 44, 2169 (1997)
•RDCs calculated from the nonionizing energy loss (NIEL)
•Determines degradation curve as a function of Dd and uses this curve to get the EOL result•Particle transport through the coverglass calculated independently from RDC calculation•Computer program (SAVANT) developed by NRL, NASA GRC, and OAI (unfunded at present) – SPENVIS?
S. Messenger, SPENVIS Workshop 2005
Choose Nonionizing Energy Loss (NIEL) Data
(Energy Dependence of Damage Coefficients)
Measure Characteristic Degradation Curve vs. Dd
(Dd=NIELxFluence) (2 e- and 1 p+ energy)
Read Off EOL Value
Determine Incident Particle Spectrum (e.g. AP8, AE8)
Calculate Slowed-Down Spectrum (SDS) (Shielding)
Calculate Dd for Mission (Integrate SDS with NIEL)
NRL Displacement Damage Dose Method
S. Messenger, SPENVIS Workshop 2005
NonIonizing Energy Loss
NIEL= Rate at which energy is lost to nonionizing events; (UNITS=MeV/cm or MeVcm2/g)
)T( dmin
E)]d,E)L[T(,T(d
E),(dNIEL(E)
Differential scattering cross section for
displacements
Recoil energy
Lindhard partition factor
S. Messenger, SPENVIS Workshop 2005
• Several calculations exist, all yielding similar results
• Notable NIEL calculations (p+, e-, , no, ions) : NRL group (NSREC, 1986-2003) Van Ginneken, 1989 NASA/JPL group (2000-2005, WINNIEL) CERN group (Huhtinen et al., 2000-2005) Akkerman and Barak, 2001 Inguimbert & Gigante (NEMO, 2005) Fischer and Thiel, U. Koln
• Especially good agreement over practical proton energies for solar cells in space (0.1-10 MeV)
NonIonizing Energy Loss
S. Messenger, SPENVIS Workshop 2005
10-4 10-3 10-2 10-1 100 101 102 103
Particle Energy (MeV)
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Si N
IEL
(M
eVcm
2 /g)
ProtonElectronNeutron
*Td = 21 eV
Si
NIEL for Si (w/Neutron)
S. Messenger, SPENVIS Workshop 2005
Choose Nonionizing Energy Loss (NIEL) Data
(Energy Dependence of Damage Coefficients)
Measure Characteristic Degradation Curve vs. Dd
(Dd = NIEL x Fluence) (1 p+ and 2 e- energies)
Read Off EOL Value
Determine Incident Particle Spectrum (e.g. AP8, AE8)
Calculate Slowed-Down Spectrum (SDS) (Shielding)
Calculate Dd for Mission (Integrate SDS with NIEL)
NRL Displacement Damage Dose Method
S. Messenger, SPENVIS Workshop 2005
Displacement Damage Dose (Dd)Unit is MeV/g is analogous to ionizing dose Rad(Si)
1)(n
refrefd )NIEL(E
NIEL(E)NIEL(E)(E))E(D
Protons: n=1
Electrons: 1<n<2
Or, for a spectrum of particles, as that found in space,
Slowed-down differential spectra
S. Messenger, SPENVIS Workshop 2005
e
1ne
ee
eeppp
p
pd dE
)MeV1(NIEL
)E(NIEL)(ENIEL
dE
)(EdR)dE(ENIEL
dE
)(EdD
•Characteristic curve is independent of particle
•Calculated NIEL gives energy dependence of damage coefficients
•4 empirically determined parameters (C,Dx,Rep,n)
Characteristic Curve
With NIEL
Measured DataNRL Displacement Damage Dose Method
108 109 1010 1011 1012
Displacement Damage Dose (MeV/g)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
No
rmal
ized
Max
imu
m P
ow
er 1 Sun, AM0T=25oC
GaAs/Ge
0.6 MeV1 MeV2.4 MeV12 MeV
Protons Electrons9.5 MeV3 MeV1 MeV0.5 MeV0.3 MeV0.2 MeV
1 MeV equiv.
Neutrons10
810
910
1010
1110
1210
1310
1410
1510
1610
170.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
No
rmal
ized
Max
imu
m P
ow
er
1 Sun, AMOGaAs/Ge
Particle Fluence (cm-2
)
Protons
Electrons0.6 MeV1 MeV2.4 MeV12 MeV
9.5 MeV3 MeV1 MeV0.5 MeV0.3 MeV0.2 MeV0.1 MeV0.05 MeV
25oC
1 MeV equiv.
Neutrons
S. Messenger, SPENVIS Workshop 2005
10-4 10-3 10-2 10-1 100 101 102 103
Particle Energy (MeV)
10-6
10-5
10-4
10-3
10-2
10-1
100
101
GaA
s N
IEL
(M
eVcm
2 /g)
ProtonElectronNeutron
*Td = 10 eV, Ga & As
GaAs
Choose Nonionizing Energy Loss (NIEL) Data
(Energy Dependence of Damage Coefficients)
Measure Characteristic Degradation Curve vs. Dd
(Dd=NIELxFluence) (2 e- and 1 p+ energy)
Read Off EOL Value
Determine Incident Particle Spectrum (e.g. AP8, AE8)
Calculate Slowed-Down Spectrum (SDS) (Shielding)
Calculate Dd for Mission (Integrate SDS with NIEL)
NRL Displacement Damage Dose Method
S. Messenger, SPENVIS Workshop 2005
• Based on the Continuous Slowing Down Approximation (CSDA)• The rate of energy loss equals that due to
the total stopping power (i.e. no energy loss fluctuations, straggling)
• Particle transport governed by range data• CSDA not expected to hold for electrons of
low energy
An Analytical Calculation Implementing the Dd Approach
S. Messenger, SPENVIS Workshop 2005
Analytical Proton Transport Model
10-4 10-3 10-2 10-1 100 101 102 103
Proton Energy (MeV)
107
108
109
1010
1011
1012
1013
1014
1015
1016
Dif
fere
nti
al F
luen
ce (
cm-2
MeV
-1)
30 mil
Uncovered
5000 km, Circular Orbit60 Inclination5 year mission
E'
E1E2
E3E4
E5
12 mil
3 mil
SiO2 coverglass
S. Messenger, SPENVIS Workshop 2005
Choose Nonionizing Energy Loss (NIEL) Data
(Energy Dependence of Damage Coefficients)
Measure Characteristic Degradation Curve vs. Dd
(Dd=NIELxFluence) (2 e- and 1 p+ energy)
Read Off EOL Value
Determine Incident Particle Spectrum (e.g. AP8, AE8)
Calculate Slowed-Down Spectrum (SDS) (Shielding)
Calculate Dd for Mission (Integrate SDS with NIEL)
NRL Displacement Damage Dose Method
S. Messenger, SPENVIS Workshop 2005
0 10 20 30 40 50SiO2 Thickness (mil)
109
1010
1011
1012
Dd (
MeV
/g) (1 Year Mission)
GaAs
5000 km, circular, 60o
108 109 1010 1011 1012
Displacement Damage Dose (MeV/g)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
No
rmal
ized
Max
imu
m P
ow
er
1 Sun, AM0T=25oC
GaAs/Ge
Incident and SDS (Isotropic) NonIonizing Energy Loss
Total Mission Dose
Pmax Degradation
NRL Displacement Damage Dose Method
10-4 10-3 10-2 10-1 100 101 102 103
Proton Energy (MeV)
107
108
109
1010
1011
1012
1013
1014
1015
1016
Dif
fere
nti
al F
luen
ce (
cm-2
MeV
-1)
3 mil
30 mil
12 mil
Uncovered
SiO2 Coverglass Thickness
5000 km, Circular Orbit60 Inclination5 year mission
10-4 10-3 10-2 10-1 100 101 102 103
Proton Energy (MeV)
10-3
10-2
10-1
100
101
GaA
s N
IEL
(M
eVcm
2/g
)
Proton
*Td = 10 eV, Ga & As
GaAs
S. Messenger, SPENVIS Workshop 2005
10-4 10-3 10-2 10-1 100 101 102 103
Slowed-Down Proton Energy (MeV)
0.0
0.2
0.4
0.6
0.8
1.0C
um
ula
tive
Fra
ctio
n o
f D
d
3 mil
30 mil
12 mil
GaAs
5000 km, Circular Orbit60 Inclination5 year mission
Cumulative Fraction of Dd
S. Messenger, SPENVIS Workshop 2005
SAVANT Dd Analysis Code
S. Messenger, SPENVIS Workshop 2005
SAVANT: Solar Array Verification and Analysis Tool (NASA, NRL, OAI)
0 10 20 30 40 50 60SiO2 Coverglass Thickness (mils)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Displacement Damage Dose (NRL) ModelEquivalent Fluence (JPL) Model
5093 km, circular, 60o orbit (1 year duration)
Nor
mal
ized
Max
imum
Pow
er D
egra
dati
onGaAs/Ge
Comparison of Results
S. Messenger, SPENVIS Workshop 2005
NRL Dd Model Pros/Cons• Pros:
– Few ground test measurements needed (3)– Ground test particle energies can be conveniently chosen
– Uniform damage deposition required over active region– Shielding algorithm is independent– Allows for rapid analysis of emerging cell technologies– Allows for easy trade studies– Can combine data from different experiments– Allows for alternate radiation particles (neutrons, alphas, etc.)
• Cons:– Lack of heritage (developed in the mid-1990s)– More suited for sufficiently thin devices (~few m)– Program currently not available to general public
S. Messenger, SPENVIS Workshop 2005
Why does the Dd Method work so well?
S. Messenger, SPENVIS Workshop 2005
The energy dependence of the NIEL closely follows the RDCs over practical energies considered for space applications
10-2 10-1 100 101 102
Energy (MeV)
10-1
100
101
102
103
Rel
ativ
e P
max
Dam
age
Co
effi
cien
t SJ GaAs/Ge2J InGaP/GaAs/Ge3J InGaP/GaAs/GeCIGSNIEL GaAsJPL MJ RDCs SRIM MJ RDCs
Protons
*Parameters normalized to value at 10 MeV
Proton NIEL Comparison vs. RDCs
S. Messenger, SPENVIS Workshop 2005
10-1 100 101 102
Energy (MeV)
10-3
10-2
10-1
100
101
102
Re
lati
ve
Pm
ax D
amag
e C
oe
ffic
ien
t Electrons
*Parameters normalized to value at 1 MeV
SJ GaAs/Ge2J InGaP/GaAs/Ge3J InGaP/GaAs/GeCIGS1 MeV Equiv. NIEL GaAs (n=1.7)1 MeV Equiv. NIEL CIGS (n=2)
Electron NIEL Comparison vs. RDCs
S. Messenger, SPENVIS Workshop 2005
Effect of Low Energy Protons on Multijunction (MJ) Solar Cells
S. Messenger, SPENVIS Workshop 2005
Monoenergetic, Unidirectional Irradiations
108 109 1010 1011 10120.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
30 keV50 keV70 keV100 keV150 keV250 keV380 keV1 MeV2 MeV3 MeV5 MeV
Proton Energy
Displacement Damage Dose (MeV/g)
Rem
ain
ing
Fac
tor
of
Pm
ax
*T. Sumita, M. Imaizumi, S. Matsuda, T. Ohshima, A. Ohi, and T. Kamiya, Proc. 19th EPVSEC, Paris, 2004.
3J InGaP2/GaAs/Ge
S. Messenger, SPENVIS Workshop 2005
300 500 700 900 1100 1300 1500 1700 19000.0
0.2
0.4
0.6
0.8
1.0
Wavelength (nm)
Qu
antu
m E
ffic
ien
cy
Solid lines: Unirradiated
Dashed lines: 1x1012 p+/cm2
50 keV Protons
InGaP/GaAs/Ge
300 500 700 900 1100 1300 1500 1700 19000.0
0.2
0.4
0.6
0.8
1.0
Wavelength (nm)
Qu
antu
m E
ffic
ien
cy
Solid lines: Unirradiated
Dashed lines: 1x1012 p+/cm2
100 keV Protons
InGaP/GaAs/Ge
300 500 700 900 1100 1300 1500 1700 19000.0
0.2
0.4
0.6
0.8
1.0
Wavelength (nm)
Qu
antu
m E
ffic
ien
cy
Solid lines: Unirradiated
Dashed lines: 1x1012 p+/cm2
400 keV Protons
InGaP/GaAs/Ge
300 500 700 900 1100 1300 1500 1700 19000.0
0.2
0.4
0.6
0.8
1.0
Wavelength (nm)
Qu
antu
m E
ffic
ien
cy
Solid lines: Unirradiated
Dashed lines: 1x1012 p+/cm2
1 MeV Protons
InGaP/GaAs/Ge
Proton-Induced QE Degradation in MJ Cells
50 keV protons
100 keV protons
400 keV protons
1 MeV protons
S. Messenger, SPENVIS Workshop 2005
108 109 1010 1011 10120.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
30 keV50 keV70 keV100 keV150 keV250 keV380 keV1 MeV2 MeV3 MeV5 MeV
Proton Energy
Displacement Damage Dose (MeV/g)
Rem
ain
ing
Fac
tor
of
Pm
ax
Monoenergetic, Unidirectional Irradiations
• Typical ground test conditions (not space conditions)• Nonuniform vacancy distribution – Bragg Peak at end of track• Different energies can preferentially degrade one sub-junction• This effect is not seen in 1 MeV Electron irradiation
Top cell degradation
Middle cell degradation
*T. Sumita, M. Imaizumi, S. Matsuda, T. Ohshima, A. Ohi, and T. Kamiya, Proc. 19th EPVSEC, Paris, 2004.
*Results from SRIM 2003 v.26 (www.srim.org)
10-2 10-1 100 101 102 103
Depth (m)
10-1
100
101
102
Va
ca
nc
y P
rod
uc
tio
n R
ate
(#
/m
/ion
) 63.1 keV Mono, Norm251 keV Mono, Norm1 MeV Mono, Norm
GaAs GeInGaP
S. Messenger, SPENVIS Workshop 2005
Spectrum, Omnidirectional Irradiation
• Representative of exposure in the space radiation environment
• The vacancy distribution profile is nearly uniform over active region
*Results from SRIM 2003 v.26 using special input file (TRIM.DAT) which specifies random incident angle and energy to simulate L2 spectrum (3 mil SiO2)
No special effects due to low energy protons apparent!
10-2 10-1 100 101 102 103
Depth (m)
10-2
10-1
100
101
102
Va
ca
nc
y P
rod
uc
tio
n R
ate
(#
/m
/ion
)
L2 Spectrum, 3 mils SiO2
GaAs GeInGaP
S. Messenger, SPENVIS Workshop 2005
MJ Radiation Response Analysis Methodology
• Space radiation environment produces virtually uniform vacancy distribution throughout cell– To reproduce this with a monoenergetic, unidirectionally incident
particle, we need a fully penetrating proton (>1 MeV)
– NO LOW ENERGY PROTON IRRADIATION NECESSARY
• Total damage induced in cell (i.e. total number of vacancies) in space can be quantified in terms of Displacement Damage Dose (Dd)
– Value of Dd is calculated by integrating the product of the slowed-down spectrum and the NIEL over energy
– Validation exists for several MJ technologies
– Enables quick and inexpensive qualification of new technologies
– SPENVIS Implementation Soon!!!
1) Incident differential radiation spectra (SPENVIS)
2) Calculation of the “slowed-down” spectra after having passed through shielding (analytical, MULASSIS)
3) Calculation of the total Dd for the mission (MULASSIS)
4) Determination of the expected cell degradation (to be added, need characteristic curve info, i.e. C, Dx, n, Rep)
SPENVIS ImplementationThere are four basic components involved in this calculation:
MULASSIS is the enabling tool!
S. Messenger, SPENVIS Workshop 2005
Walk Through SPENVIS –Orbit Generation
S. Messenger, SPENVIS Workshop 2005
Walk Through SPENVIS –Incident Particle Spectra
S. Messenger, SPENVIS Workshop 2005
Walk Through SPENVIS –Shielding (Slowed Down Spectra) and Equiv. Dd
x
x
x
x
Run
• Fluence – gives slowed down spectra
• NIEL option – performs integration with NIEL to give mission Dd (not fully operational)
S. Messenger, SPENVIS Workshop 2005
5093 km, circular, 57 degree, 1 year, 12 mils SiO2/Si
1.E+08
1.E+09
1.E+10
1.E+11
1.E+12
1.E+13
1.E+14
1.E+15
1.E+16
1.E+17
1.E-03 1.E-02 1.E-01 1.E+00 1.E+01
Electron Energy (MeV)
Dif
fere
nti
al S
pe
ctr
a (
e/c
m2 /M
eV
)
Incident Spectrum
Slowed-Down Spectrum (In-House Calc)
Slowed-Down Spectrum (MULASSIS)
1.E+06
1.E+07
1.E+08
1.E+09
1.E+10
1.E+11
1.E+12
1.E+13
1.E+14
1.E+15
1.E+16
1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03
Proton Energy (MeV)
Dif
fere
nti
al S
pe
ctr
a (
p/c
m2 /M
eV
)
Incident Spectrum
Slowed-Down Spectra (In-House Calc)
Slowed-Down Spectrum (MULASSIS)
Calculations Made External to SPENVIS –Equivalent Value of Dd
• Slowed-down spectra exported as TXT file from MULASSIS• Read into MS Excel and integrated with NIEL to give Dd• Also calculated by in-house NRL program for comparison
Proton Dd (MeV/g) Electron Dd (MeV/g)MULASSIS 3.8E+10 5.4E+08In-House Calc 3.3E+10 6.0E+08
protonselectrons
e
ne
ee
eeppp
p
pd dE
)MeV(NIEL
)E(NIEL)(ENIEL
dE
)(EdR)dE(ENIEL
dE
)(EdD
1
1
S. Messenger, SPENVIS Workshop 2005
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
1.E+10
1.E+11
1.E+12
1.E+13
1.E+14
1.E+15
1.E+16
1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03
Proton Energy (MeV)
Dif
fere
nti
al S
pe
ctr
a (
p/c
m2 /M
eV
)
Incident Spectra
Slowed-Down Spectra (Mathcad)
MULASSIS (10,000,000 particles)
MATHCAD RESULT Dd= 1.85E+07 MeV/gMULASSIS RESULT Dd= 1.50E+07 MeV/g
% 1.91E+01
*5093 km, circular, 57 degree, 1 year, 1000 mils Al/Si
Thick Shielding Example
S. Messenger, SPENVIS Workshop 2005
Calculations Made External to SPENVIS –Solar Cell End-of-Life Power Output
x
ddmax
D
DlogC
P
)D(P11
0
108108 109 1010 1011
Displacement Damage Dose (MeV/g)
0.5
0.7
0.9
1.1
Nor
m P
mp
0
0.312.5101212
Emcore 3J Cells
Energy (MeV)
electron
proton C = 0.199
Dx = 1.2x109 MeV/g
n = 1.8Rep = 0.17
(c, Dx, n, Rep)
108108 109 1010 1011
Displacement Damage Dose (MeV/g)
0.5
0.7
0.9
1.1
Nor
m P
mp
0
0.312.5100.6112
Spectrolab EOL 3J Cells n/p cells
Energy (MeV)
electron
Data from Marvin 2000
proton
C = 0.3
Dx = 3x109 MeV/g
n = 1.6Rep = 0.3
108108 109 1010 1011
Displacement Damage Dose (MeV/g)
0.5
0.7
0.9
1.1
Nor
m P
mp
0
0.20.415100.611.6
Tecstar 3J Cells
Energy (MeV)
electron
proton C = 0.25
Dx = 1x109 MeV/g
n = 1.09Rep = 0.17
Independent Variables
S. Messenger, SPENVIS Workshop 2005
•Mulassis agrees very well with the analytical slab geometry model for protons
•Mulassis allows for multiple interfaces and layers
•Effect of electrons usually minimal (However, MULASSIS is probably better since analytical model assumes CSDA)
•Could be extended for use with heavy ions and neutrons (NIEL is available for most cases)
•Could be used for other devices where displacement damage is an important damage mechanism (e.g. LED light output, CCD degradation, transistor gain, etc.)
Notes
S. Messenger, SPENVIS Workshop 2005
•Continue to work with ESTEC, BIRA, and QINETIQ to further implement the method and perform benchmark tests
•Develop characteristic radiation degradation curves for current state-of-the-art solar cell technologies
•Develop capabilities for other devices and irradiation particles
Future Work
S. Messenger, SPENVIS Workshop 2005