Model for determining energetic particle interactions with ESP
S. Wieman, L. Didkovsky, D. Judge
USC Space Sciences Center
EVE SpaceWx and
Operations Workshop
Oct. 6-8, 2010
LASP – Univ. of Colorado
Proton effects analysis needed for
•Shielding vs. mass optimization/PDR request for action
•Comparing proton noise in “dark” channel to other channels
SDO 5-year Proton Fluences
(from Rad. Analysis for SDO)
1.0E+13
Proton fluence with energy >E (#/cm^2)
Surface Incident
1.0E+12
Through shielding
(12mm Al+Ni)
1.0E+11
1.0E+10
1.0E+09
1.0E+08
1.0E+07
1.0E+05
1.0E+06
1.0E+07
Proton Energy, E (eV)
1.0E+08
1.0E+09
2
Geometry issues
3 particles with the same
initial energy follow different
paths to a target point on the
detector. Each traverse a
different amount of material
in traversing the shielding and
thus reach the detector with
different reduced energies.
3
SolidWorks based analysis
4
Energy (MeV)
Stopping Power (MeV cm2/g)
Stopping Power (MeV cm2/g)
Energy deposition
Energy (MeV)
From N.I.S.T. PSTAR (http://physics.nist.gov)
For each incident energy, Ei, mean per particle displacement damage, ionizing dose or signal contamination
may be calculated from:
t1
Er = Ei − ∫ σ T ( E , Z )dx
0
t2
ED = ∫ σ n ( E )dx ≈ σ n ( Er ) ⋅ t 2 *
0
t2
EI = ∫ σ e ( E )dx ≈ σ e ( Er ) ⋅ t 2 *
0
EI , D ( Ei ) ≈
N
∑σ
j =1
e, n
( Er j ) ⋅ t 2 j
N
where:
Er = Proton reduced energy (after slowing in shielding)
Ei = proton incident energy
EI = Energy deposited in electronic interactions
ED = Energy deposited in displacement interactions
σT, σn, σe = Total, nuclear, electronic stopping power, respectively
t1, t2 = thickness of shielding layers, target, respectively
* - approximation holds for small t2
5
. . . or expressed as expected detector count rates:
EI
Cp =
⋅ φ p ( Ei ) ⋅ Ge
eV
3.63 −
e
Where:
Cp = DN counts per 0.25 sec
3.63 eV/e- = average energy per electron-hole pair, Si
ϕp(Ei) = input proton spectrum (adjusted for input solid angle)
Ge = electrometer gain (0.25 sec count = 40 fA)
Verifying dark channel correction
Average number of electron hole pairs
generated per incident proton
25000
20000
15000
Ch3
Ch1
10000
Ch9
Oct. 29, 2003 and Nov. 2, 2003 1 AU proton
fluxes are from GOES EPEAD from the Space
Weather Prediction Center, Boulder, CO,
National Oceanic and Atmospheric
Administration (NOAA), US Dept. of
Commerce
5000
0
0
20
40
60
80
100
120
140
160
180
200
Proton incident energy (MeV)
Ch1-Ch3
Ch9-Ch3
Difference in proton related counts
(.25 sec counts)
Moderate fluxes
High fluxes
(11/2/2003)
(10/29/2003)
2.1
24.3
1.9
31.6
7
Non-isotropic Example
Verifying dark channel correction
7000
Average number of electron hole pairs
generated per incident proton
6000
5000
4000
Ch3
3000
Ch1
Ch9
2000
Oct. 29, 2003 and Nov. 2, 2003 1 AU proton
fluxes are from GOES EPEAD from the Space
Weather Prediction Center, Boulder, CO,
National Oceanic and Atmospheric
Administration (NOAA), US Dept. of
Commerce
1000
0
0
20
40
-1000
60
80
100
120
140
160
180
200
Proton incident energy (MeV)
Ch1-Ch3
Ch9-Ch3
Difference in proton related counts
(.25 sec counts)
Moderate fluxes
High fluxes
(11/2/2003)
(10/29/2003)
0.0
5.4
2.0
38.5
9
Model Verification
Model is “spot checked” for discrete Incident Energies, shielding and target
thicknesses using Stopping and Ranges of Ions in Matter (SRIM) transport code
(www.srim.org)
Si Ionizing Energy deposition
(eV/proton)
130000
Comparison SRIM to SW proton simulation - 12mm Al over
6um Silicon
110000
SW
radiationmodel
model
SolidWorks
90000
SRIM results
70000
50000
30000
10000
40
60
80
100
Surface Incident Proton Energy (MeV)
120
10
Planned Improvements
Use compiled monte carlo simulation data rather than CSDA tables to represent
energy transfer and particle scattering more accurately (e.g. database assembled of
SRIM data)
J. F. Ziegler, J. P. Biersack and M. D. Ziegler, "The Stopping and Range of Ions in
Solids", by available from www.SRIM.org (2008)