Transcript Document

Displacement Damage Dose Approach
For Determining Solar Cell Degradation
In Space With Spenvis Implementation
Dr. Scott R. Messenger
SFA, Inc.
([email protected])
SPENVIS & GEANT4 workshop
Faculty Club
Leuven, Belgium
3 - 7 October 2005
Outline
• 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
S. Messenger, SPENVIS Workshop 2005
The Problem
electrons
protons
p+
p+
e-
p+
e-
COVERGLASS
e-
ACTIVE CELL
SUBSTRATE
e-
• Omnidirectional, isotropic, energy
spectrum in space
p+
• Unidirectional, normally incident,
monoenergetic irradiation of bare
solar cells on the ground
S. Messenger, SPENVIS Workshop 2005
PANEL
p+
p+
*Planar, slab geometry
e-
p+
Normalized Maximum Power
Pmax Degradation Curves for
GaAs/Ge Solar Cells (JPL, 1991)
1.0
GaAs/Ge
0.9
1 Sun, AMO
o
25 C
0.8
0.7
0.6
Protons
0.5
9.5 MeV
3 MeV
1 MeV
0.5 MeV
0.3 MeV
0.2 MeV
0.1 MeV
0.05 MeV
0.4
0.3
0.2
0.1
0.0
8
10
9
10
10
10
Electrons
0.6 MeV
1 MeV
2.4 MeV
12 MeV
10
11
10
12
10
13
10
14
10
-2
Particle Fluence (cm )
S. Messenger, SPENVIS Workshop 2005
15
10
16
10
17
The Solution
• 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
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
JPL Equivalent Fluence Method
Measure PV Degradation
Curves (~4 electron and
~8 proton energies)
Determine Incident Particle
Spectrum (e.g. AP8)
Determine Damage
Coefficients for
Uncovered Cells
1 MeV Electron
Degradation Curve
Calculate Damage Coefficients
for Isotropic Particles w/
Coverglasses of Varied
Thickness
Calculate Equivalent 1 MeV Electron
Fluence for Orbit (EQGAFLUX)
Read Off EOL Values
S. Messenger, SPENVIS Workshop 2005
Electron Damage Coefficients
JPL Equivalent
Fluence Method
102
Electron and Proton
Fluence Data (GaAs/Ge, 1991)
GaAs/Ge
0.9
1 Sun, AMO
o
25 C
75% BOL
0.8
0.6
Normal incidence
no coverglass
100
Coverglass Thickness
0 mil
1 mil
3 mil
6 mil
12 mil
20 mil
30 mil
60 mil
10-1
10-2
10-1
100
101
102
Electron Energy (MeV)
Protons
0.5
Proton Damage Coefficients
9.5 MeV
3 MeV
1 MeV
0.5 MeV
0.3 MeV
0.2 MeV
0.1 MeV
0.05 MeV
0.4
0.3
0.2
0.1
0.0
8
10
101
10-3
0.7
9
10
10
10
102
*Relative to 10 MeV proton normal
incidence data, w/o coverglass
Electrons
0.6 MeV
1 MeV
2.4 MeV
12 MeV
10
11
10
12
10
13
10
14
10
-2
Particle Fluence (cm )
15
10
16
10
17
Relative Pmax Damage Coefficient
Normalized Maximum Power
1.0
Relative Pmax Damage Coefficient
*Relative to 1 MeV normal
incidence data, w/o coverglass
Normal incidence
no coverglass
101
100
Coverglass
Thickness
0 mil
1 mil
3 mil
6 mil
12 mil
20 mil
30 mil
60 mil
10-1
10-2
10-2
10-1
100
Proton Energy (MeV)
S. Messenger, SPENVIS Workshop 2005
101
102
Equivalent 1 MeV Electron Fluence
1MeV electron
dp (Ep )
de (E e )

 RDC(E e , t)dE e  Cpe 
 RDC(Ep , t)dEp
dEe
dEp
where the RDCs for a coverglass thickness t is:
/2
1
RDC(E,t) 
RDC(E0 ,0)2 sin d

4 0
(for electrons*)
where the energy loss is determined from
t 

E0 (E, , t )  R R(E) 
cos  

1
R(E) is the range
*for protons, another term is included to account for end-of-track effects
S. Messenger, SPENVIS Workshop 2005
JPL Equivalent Fluence Method
Initial Omnidirectional Spectrum
Proton Damage Coefficients
*
R
e
l
a
t
i
v
e
t
o
1
0
M
e
V
n
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r
m
a
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a
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w
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b
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P
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a
x
1
1
0
10 13
10 12
10 10
10 9
10 8
C
o
v
e
r
g
l
a
s
s
T
h
i
c
k
n
e
s
s
0
1
0
10 11
1
1
0
5000 km, circular, 600 orbit
(1 year duration)
10 7 -1
10
10 0
10 1
10 2
10 3
2
1
0
2
1
0
Proton Energy (MeV)
0
1
0
1
1
0
2
1
0
1 MeV Electron Pmax Degradation
1
.
0
G
a
A
s
G
a
A
s
/
G
e
(
J
P
L
,
1
9
9
0
)
o
1
S
u
n
,
A
M
0
,
2
5
C
0
.
9
0
.
8
o
5
0
0
0
k
m
,
c
i
r
c
u
l
a
r
,
6
0
o
r
b
i
t
(
1
y
e
a
r
d
u
r
a
t
i
o
n
)
0
.
7
NormalizedP max Degradtion
-/cm 2)
1
1
0
P
r
o
t
o
n
E
n
e
r
g
y
(
M
e
V
)
Equivalent 1 MeV Electron Fluence
1
6
1
0
0
m
i
l
1
m
i
l
3
m
i
l
6
m
i
l
1
2
m
i
l
2
0
m
i
l
3
0
m
i
l
6
0
m
i
l
RelativP max DamgeCoficnt
Fluence (cm2MeV)-1
10 14
0
.
6
0
.
5
1
5
1
0
0
.
4
0
.
3
0
.
2
1MeVElctronFue(
0
.
1
1
4
1
0
0
1
0
2
0
3
0
4
0
5
0
6
0
7
0
8
0
S
i
O
C
o
v
e
r
g
l
a
s
s
T
h
i
c
k
n
e
s
s
(
m
i
l
)
2
0
.
0
1
4
1
0
1
5
1
0
1
6
1
7
1
0
1
0
-2
1
M
e
V
E
l
e
c
t
r
o
n
F
l
u
e
n
c
e
(
e
/
c
m
)
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
NRL Displacement Damage Dose Method
Choose Nonionizing Energy
Loss (NIEL) Data
(Energy Dependence of Damage
Coefficients)
Determine Incident Particle
Spectrum (e.g. AP8, AE8)
Calculate Slowed-Down
Spectrum (SDS) (Shielding)
Measure Characteristic
Degradation Curve vs. Dd
(Dd=NIELxFluence)
(2 e- and 1 p+ energy)
Calculate Dd for Mission
(Integrate SDS with NIEL)
Read Off EOL Value
S. Messenger, SPENVIS Workshop 2005
NonIonizing Energy Loss
NIEL= Rate at which energy is lost to nonionizing events;
(UNITS=MeV/cm or MeVcm2/g)

NIEL(E) 

min( Td )
 d(,E) 

T( ,E)L[T( ,E)]d
 d 
Differential scattering
cross section for
displacements
Lindhard partition
factor
Recoil energy
S. Messenger, SPENVIS Workshop 2005
NonIonizing Energy Loss
• Several calculations exist, all yielding similar
results
• Notable NIEL calculations (p+, e-, a, 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)
S. Messenger, SPENVIS Workshop 2005
NIEL for Si (w/Neutron)
101
Si
Si NIEL (MeVcm 2/g)
100
*Td = 21 eV
10-1
Proton
Electron
Neutron
10-2
10-3
10-4
10-5
10-6
10-4
10-3
10-2
10-1
100
101
Particle Energy (MeV)
S. Messenger, SPENVIS Workshop 2005
102
103
NRL Displacement Damage Dose Method
Choose Nonionizing Energy
Loss (NIEL) Data
(Energy Dependence of Damage
Coefficients)
Determine Incident Particle
Spectrum (e.g. AP8, AE8)
Calculate Slowed-Down
Spectrum (SDS) (Shielding)
Measure Characteristic
Degradation Curve vs. Dd
(Dd = NIEL x Fluence)
(1 p+ and 2 e- energies)
Calculate Dd for Mission
(Integrate SDS with NIEL)
Read Off EOL Value
S. Messenger, SPENVIS Workshop 2005
Displacement Damage Dose (Dd)
Unit is MeV/g is analogous to ionizing dose Rad(Si)
(n1)
Protons: n=1

 NIEL(E)
Dd (Eref )  (E)  NIEL(E)  

 NIEL(E ref ) 
Electrons: 1<n<2
Or, for a spectrum of particles, as that found in space,
Dd 

d(Ep )
dEp
 NIEL (Ep )dE p  Rep

 NIEL (Ee ) 
d(Ee )
 NIEL (Ee )

dEe
NIEL
(
1
MeV
)


Slowed-down
differential spectra
S. Messenger, SPENVIS Workshop 2005
n1
dEe
NRL Displacement Damage Dose Method
1.0
GaAs/Ge
0.9
1 Sun, AMO
o
25 C
0.8
Characteristic Curve
1.0
0.7
0.6
Protons
9.5 MeV
3 MeV
1 MeV
0.5 MeV
0.3 MeV
0.2 MeV
0.1 MeV
0.05 MeV
0.5
0.4
0.3
0.2
0.1
0.0
8
10
10
9
10
10
Electrons
Neutrons
0.6 MeV
1 MeV
2.4 MeV
12 MeV
1 MeV equiv.
10
11
10
12
13
10
14
10
10
15
16
10
10
17
-2
Particle Fluence (cm )
With NIEL
101
GaAs
GaAs NIEL (MeVcm 2/g)
100
*Td = 10 eV, Ga & As
Normalized Maximum Power
Normalized Maximum Power
Measured Data
GaAs/Ge
0.9
1 Sun, AM0
T=25oC
0.8
0.7
0.6
0.5
0.4
0.3
0.2
Protons
9.5 MeV
3 MeV
1 MeV
0.5 MeV
0.3 MeV
0.2 MeV
Electrons
0.6 MeV
1 MeV
2.4 MeV
12 MeV
Neutrons
1 MeV equiv.
0.1
0.0
108
109
1010
1011
1012
-1
10
-2
10
Displacement Damage Dose (MeV/g)
Proton
Electron
Neutron
•Characteristic curve is independent of particle
10-3
•Calculated NIEL gives energy dependence of
damage coefficients
10-4
10-5
10-6
10-4
10-3
10-2
10-1
100
101
102
103
•4 empirically determined parameters (C,Dx,Rep,n)
Particle Energy (MeV)
S. Messenger, SPENVIS Workshop 2005
NRL Displacement Damage Dose Method
Choose Nonionizing Energy
Loss (NIEL) Data
(Energy Dependence of Damage
Coefficients)
Determine Incident Particle
Spectrum (e.g. AP8, AE8)
Calculate Slowed-Down
Spectrum (SDS) (Shielding)
Measure Characteristic
Degradation Curve vs. Dd
(Dd=NIELxFluence)
(2 e- and 1 p+ energy)
Calculate Dd for Mission
(Integrate SDS with NIEL)
Read Off EOL Value
S. Messenger, SPENVIS Workshop 2005
An Analytical Calculation
Implementing the Dd Approach
• 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
S. Messenger, SPENVIS Workshop 2005
Differential Fluence (cm -2MeV-1)
Analytical Proton Transport Model
1016
E1
Uncovered
1015
E3
1014
1013
E5
3 mil
12 mil
1011
30 mil
1010
108
107
10-4
E4
SiO2 coverglass
1012
109
E2
E'
5000 km, Circular Orbit
60 Inclination
5 year mission
10-3
10-2
10-1
100
101
Proton Energy (MeV)
S. Messenger, SPENVIS Workshop 2005
102
103
NRL Displacement Damage Dose Method
Choose Nonionizing Energy
Loss (NIEL) Data
(Energy Dependence of Damage
Coefficients)
Determine Incident Particle
Spectrum (e.g. AP8, AE8)
Calculate Slowed-Down
Spectrum (SDS) (Shielding)
Measure Characteristic
Degradation Curve vs. Dd
(Dd=NIELxFluence)
(2 e- and 1 p+ energy)
Calculate Dd for Mission
(Integrate SDS with NIEL)
Read Off EOL Value
S. Messenger, SPENVIS Workshop 2005
NRL Displacement Damage Dose Method
NonIonizing Energy Loss
10
101
1014
SiO2 Coverglass Thickness
1013
10
3 mil
12
12 mil
1011
10
GaAs
Uncovered
15
GaAs NIEL (MeVcm 2/g)
Differential Fluence (cm -2MeV-1)
Incident and SDS (Isotropic)
1016
30 mil
10
109
108
107
10-4
5000 km, Circular Orbit
60 Inclination
5 year mission
10-3
10-2
10-1
100
101
102
103
Proton Energy (MeV)
*Td = 10 eV, Ga & As
100
Proton
10-1
10-2
10-3
10-4
10-3
10-2
10-1
100
101
102
103
Proton Energy (MeV)
1012
1.0
GaAs
Normalized Maximum Power
Total Mission Dose
5000 km, circular, 60o
(1 Year Mission)
Dd (MeV/g)
1011
1010
10
9
0
10
20
30
40
SiO2 Thickness (mil)
50
GaAs/Ge
0.9
1 Sun, AM0
T=25oC
0.8
0.7
0.6
0.5
0.4
0.3
Pmax Degradation
0.2
0.1
0.0
108
109
1010
1011
Displacement Damage Dose (MeV/g)
S. Messenger, SPENVIS Workshop 2005
1012
Cumulative Fraction of Dd
Cumulative Fraction of D d
1.0
GaAs
0.8
3 mil
0.6
12 mil
30 mil
0.4
5000 km, Circular Orbit
60 Inclination
5 year mission
0.2
0.0
10-4
10-3
10-2
10-1
100
101
102
Slowed-Down Proton Energy (MeV)
S. Messenger, SPENVIS Workshop 2005
103
SAVANT Dd Analysis Code
SAVANT: Solar Array Verification and Analysis Tool (NASA, NRL, OAI)
S. Messenger, SPENVIS Workshop 2005
Comparison of Results
1
.
0
G
a
A
s
/
G
e
0
.
9
0
.
8
0
.
7
0
.
6
o
5
0
9
3
k
m
,
c
i
r
c
u
l
a
r
,
6
0
o
r
b
i
t
(
1
y
e
a
r
d
u
r
a
t
i
o
n
)
0
.
5
0
.
4
0
.
3
NormalizedMxmuPowerDgadtion
0
.
2
D
i
s
p
l
a
c
e
m
e
n
t
D
a
m
a
g
e
D
o
s
e
(
N
R
L
)
M
o
d
e
l
E
q
u
i
v
a
l
e
n
t
F
l
u
e
n
c
e
(
J
P
L
)
M
o
d
e
l
0
.
1
0
.
0
01
02
03
04
05
06
0
S
i
O
C
o
v
e
r
g
l
a
s
s
T
h
i
c
k
n
e
s
s
(
m
i
l
s
)
2
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 mm)
– Program currently not available to general public
S. Messenger, SPENVIS Workshop 2005
Why does the Dd Method
work so well?
The energy dependence of the NIEL
closely follows the RDCs over practical
energies considered for space
applications
S. Messenger, SPENVIS Workshop 2005
Proton NIEL Comparison vs. RDCs
Relative Pmax Damage Coefficient
103
SJ GaAs/Ge
2J InGaP/GaAs/Ge
3J InGaP/GaAs/Ge
CIGS
NIEL GaAs
JPL MJ RDCs
SRIM MJ RDCs
Protons
102
101
100
*Parameters normalized to value at 10 MeV
10-1
10-2
10-1
100
Energy (MeV)
S. Messenger, SPENVIS Workshop 2005
101
102
Electron NIEL Comparison vs. RDCs
Relative Pmax Damage Coefficient
102
Electrons
101
100
SJ GaAs/Ge
2J InGaP/GaAs/Ge
3J InGaP/GaAs/Ge
CIGS
1 MeV Equiv. NIEL GaAs (n=1.7)
1 MeV Equiv. NIEL CIGS (n=2)
10-1
10-2
*Parameters normalized to value at 1 MeV
10-3
10-1
100
101
Energy (MeV)
S. Messenger, SPENVIS Workshop 2005
102
Effect of Low Energy Protons on
Multijunction (MJ) Solar Cells
S. Messenger, SPENVIS Workshop 2005
Monoenergetic, Unidirectional Irradiations
3J InGaP2/GaAs/Ge
Remaining Factor of P max
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
108
Proton Energy
30 keV
50 keV
70 keV
100 keV
150 keV
250 keV
380 keV
1 MeV
2 MeV
3 MeV
5 MeV
109
1010
1011
Displacement Damage Dose (MeV/g)
*T. Sumita, M. Imaizumi, S. Matsuda, T. Ohshima, A.
Ohi, and T. Kamiya, Proc. 19th EPVSEC, Paris, 2004.
S. Messenger, SPENVIS Workshop 2005
1012
Proton-Induced QE Degradation in MJ Cells
1.0
1.0
InGaP/GaAs/Ge
InGaP/GaAs/Ge
0.8
Quantum Efficiency
Quantum Efficiency
0.8
0.6
50 keV
protons
50
keV Protons
0.4
Solid lines: Unirradiated
Dashed lines: 1x1012 p+/cm2
0.2
0.0
300
500
700
900
1100
1300
1500
0.6
100 keV
protons
100
keV Protons
0.4
Solid lines: Unirradiated
Dashed lines: 1x1012 p+/cm2
0.2
1700
0.0
300
1900
500
700
900
1100
Wavelength (nm)
InGaP/GaAs/Ge
1700
1900
InGaP/GaAs/Ge
0.8
Quantum Efficiency
0.8
Quantum Efficiency
1500
1.0
1.0
0.6
400 keV
protons
400
keV Protons
0.4
Solid lines: Unirradiated
Dashed lines: 1x1012 p+/cm2
0.2
0.0
300
1300
Wavelength (nm)
500
700
900
1100
1300
1500
0.6
1 MeV
protons
1
MeV Protons
0.4
Solid lines: Unirradiated
Dashed lines: 1x1012 p+/cm2
0.2
1700
1900
0.0
300
500
700
Wavelength (nm)
S. Messenger, SPENVIS Workshop 2005
900
1100
1300
Wavelength (nm)
1500
1700
1900
Monoenergetic, Unidirectional Irradiations
Top cell degradation
InGaP
GaAs
Ge
1.0
63.1 keV Mono, Norm
251 keV Mono, Norm
1 MeV Mono, Norm
101
100
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
10-1
10-2
10-1
100
101
102
Depth (mm)
103
0.0
108
Proton Energy
30 keV
50 keV
70 keV
100 keV
150 keV
250 keV
380 keV
1 MeV
2 MeV
3 MeV
5 MeV
109
Middle cell degradation
1010
1011
1012
Displacement Damage Dose (MeV/g)
*Results from SRIM 2003 v.26
(www.srim.org)
•
•
•
•
Remaining Factor of P max
Vacancy Production Rate (#/mm/ion)
102
*T. Sumita, M. Imaizumi, S. Matsuda, T. Ohshima, A.
Ohi, and T. Kamiya, Proc. 19th EPVSEC, Paris, 2004.
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
S. Messenger, SPENVIS Workshop 2005
Spectrum, Omnidirectional Irradiation
InGaP
Vacancy Production Rate (#/mm/ion)
102
GaAs
Ge
L2 Spectrum, 3 mils SiO2
*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)
101
100
10-1
10-2
10-2
10-1
100
101
102
103
Depth (mm)
•
•
Representative of exposure in the space radiation environment
The vacancy distribution profile is nearly uniform over active region
No special effects due to low energy protons apparent!
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 sloweddown spectrum and the NIEL over energy
– Validation exists for several MJ technologies
– Enables quick and inexpensive qualification of new technologies
– SPENVIS Implementation Soon!!!
SPENVIS Implementation
There are four basic components involved in
this calculation:
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)
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
S. Messenger, SPENVIS Workshop 2005
Run
• Fluence – gives slowed down spectra
• NIEL option – performs integration with NIEL
to give mission Dd (not fully operational)
x
x
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
5093 km, circular, 57 degree, 1 year, 12 mils SiO2/Si
1.E+17
Differential Spectra (e/cm 2/MeV)
Differential Spectra (p/cm 2/MeV)
1.E+16
1.E+15
1.E+14
1.E+13
protons
1.E+12
1.E+11
1.E+10
1.E+09
Incident Spectrum
Slowed-Down Spectra (In-House Calc)
Slowed-Down Spectrum (MULASSIS)
1.E+08
1.E+07
1.E+06
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
electrons
1.E+16
1.E+15
1.E+14
1.E+13
1.E+12
1.E+11
1.E+10
Incident Spectrum
Slowed-Down Spectrum (In-House Calc)
Slowed-Down Spectrum (MULASSIS)
1.E+09
1.E+08
1.E-03
1.E-02
Dd 

d(Ep )
dEp
MULASSIS
In-House Calc
 NIEL (Ep )dE p  Rep
1.E-01
1.E+00
1.E+01
Electron Energy (MeV)
Proton Energy (MeV)

 NIEL (Ee ) 
d(E e )
 NIEL (E e )

dEe
 NIEL (1MeV ) 
Proton Dd (MeV/g)
3.8E+10
3.3E+10
S. Messenger, SPENVIS Workshop 2005
n1
dEe
Electron Dd (MeV/g)
5.4E+08
6.0E+08
Thick Shielding Example
*5093 km, circular, 57 degree, 1 year, 1000 mils Al/Si
Differential Spectra (p/cm 2/MeV)
1.E+16
1.E+15
1.E+14
1.E+13
1.E+12
1.E+11
1.E+10
1.E+09
Incident Spectra
Slowed-Down Spectra (Mathcad)
MULASSIS (10,000,000 particles)
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
1.E+01
1.E+02
1.E+03
Proton Energy (MeV)
MATHCAD RESULT
MULASSIS RESULT
Dd=
Dd=
%
1.85E+07
1.50E+07
1.91E+01
S. Messenger, SPENVIS Workshop 2005
MeV/g
MeV/g
Calculations Made External to SPENVIS –
Solar Cell End-of-Life Power Output
1.1
Emcore 3J Cells
0.9
Norm Pmp
 Dd 
Pmax (Dd )
 1  C  log1 

P0
D
x

Energy (MeV)
proton
0.7
electron
0.3
1
2.5
10
1
2
12
0.5
0 108
C = 0.199
Dx = 1.2x109 MeV/g
Independent Variables
n = 1.8
Rep = 0.17
109
1010
1011
(c, Dx, n, Rep)
Displacement Damage Dose (MeV/g)
1.1
1.1
Tecstar 3J Cells
Spectrolab EOL 3J Cells
n/p cells
0.7
electron
Norm Pmp
Norm Pmp
proton
0.3
1
2.5
10
0.6
1
12
Energy (MeV)
0.9
Energy (MeV)
0.9
C = 0.3
Dx = 3x109 MeV/g
n = 1.6
Rep = 0.3
0.2
0.4
1
5
10
0.6
1
1.6
proton
0.7
electron
Data from Marvin 2000
0.5
8
0 10
109
1010
Displacement Damage Dose (MeV/g)
1011
0.5
8
0 10
C = 0.25
Dx = 1x109 MeV/g
n = 1.09
Rep = 0.17
109
1010
Displacement Damage Dose (MeV/g)
S. Messenger, SPENVIS Workshop 2005
1011
Notes
•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.)
S. Messenger, SPENVIS Workshop 2005
Future Work
•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
S. Messenger, SPENVIS Workshop 2005