11/12/2015nasa-jsc and dias1 study of sensitivity fading of cr-39 detectors during long time...
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04/20/23 NASA-JSC and DIAS 1
Study of Sensitivity Fading of CR-39 Detectors during Long
Time ExposureD. Zhoua, b, D. O’Sullivanc, E. Semonesa,
N. Zappa, E.R. Bentond
aJohnson Space Center - NASA, 2101 Nasa Parkway, Houston, TX 77058, USA
bUniversities Space Research Association, 3600 Bay Area Blvd, Houston, TX 77058, USA
cDublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland
dEril Research Inc., 1110 Innovation Way, Suite 100, Stillwater, OK 74074, USA
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The Role of CR-39 Detectors
in Space Studies
Measurement of
(1) LET (Linear Energy Transfer)
(2) Dose and Dose Equivalent
(3) Charge Spectrum of GCR
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Radiation Field in Low Earth Orbit
GCR (Galactic Cosmic Rays)
Solar Energetic Particles
SAA (South Atlantic Anomaly)
Albedo Neutrons
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Radiobiological Impact on AstronautsDominated by high LET (≥ 5 keV/µm water)
CR-39 detectors are most appropriate
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Some Space Missions
Which Employed CR-39 Detectors
LDEF (5.8 Years)
EUROMIR (6 Months)
Matroshka-1 (616 Days)
Matroshka-2 (367 Days)
ISS Expeditions (> 6 Months)
DOBIES (15-400 days)
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Photo of Matroshka in Space
04/20/23 NASA-JSC and DIAS 7
Fading of CR-39 Sensitivity Was observed for all CR-39 detectors
with long time exposure.
Compared to TEPC data, results measured
with CR-39 are low.
Results must be corrected for fading of
latent tracks irrespective of source. Use
“Fe peak” of exposed detector events
compare with accelerator data.
04/20/23 NASA-JSC and DIAS 8
A correction formula was found:Sc = So/(1-(a+bT))
where So = etch rate ratio before correction
Sc = corrected value of etch rate ratio
Sc1 = So1/(1-(a+bT1))
Sc2 = So2/(1-(a+bT2))
for exposure times T1 and T2
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Table 1: Fading Comparison
for different exposure time
T (a + bT) 1 – (a + bT) Sc/So
(Month)
6 0.0242 0.9758 1.0248
12 0.0388 0.9612 1.0404
24 0.0682 0.9318 1.0731
04/20/23 NASA-JSC and DIAS 10
Major / MinorLET
before Correction
LET
after Correction
(µm) (keV/µm water) (keV/µm water)
Matroshka-1
33.3 / 23.3
39 / 7
115.45
116.04
135.83
136.47
33.8 / 21 116.88 137.38
36.5 / 17
38 / 21
118.05
117.20
138.64
137.72
ISS-Expedition 12
37.5 / 20.7 128.5 136.82
37.7 / 12 129.76 138.12
Table 2: Comparison of LET before and aftercorrection of CR-39 sensitivity
04/20/23 NASA-JSC and DIAS 11
Table 3: Radiation measured without and with fading correction for CR-39 sensitivity (values include background)
Mission
(Time)
Exposure
Position
Absorbed Dose
(≥10keV/µm water)
Dose Equi. (ICRP60)
(≥ 10 keV/µm water)
Q
Factor
(Days) (mGy) (mSv)
Matroshka-1
(616)
P1
Eye
Stomach
R1
R2
29.90^/ 36.94*
14.94 / 21.60
14.96 / 18.89
13.90 / 17.93
13.85 / 17.55
270.97^/ 437.00*
176.59 / 274.82
156.95 / 246.13
148.74 / 217.31
135.29 / 215.04
9.06^/ 11.83*
11.82 / 12.72
10.49 / 13.03
10.70 / 12.12
9.77 / 12.25
Matroshka-2
(367)
P1
Eye
Stomach
R2
10.86 / 12.90
9.13 / 10.99
8.40 / 9.66
11.23 / 12.97
121.10 / 150.66
106.88 / 134.48
96.23 / 118.82
123.85 / 152.16
11.15 / 11.68
11.71 / 12.24
11.46 / 12.30
11.03 / 11.73
Expedition 12
(190)
TEPC
TESS
SMP327
SMP442
5.31 / 6.19
4.92 / 6.22
5.31 / 6.83
7.99 / 10.59
60.06 / 69.03
59.21 / 68.89
68.98 / 78.48
89.05 / 105.61
11.32 / 11.15
12.04 / 11.08
12.98 / 11.49
11.14 / 9.97
Expedition 13
(183)
TEPC
TESS
SMP442
4.90 / 6.23
4.55 / 6.18
7.98 / 9.31
65.33 / 74.20
64.09 / 73.39
94.90 / 109.95
13.33 / 11.91
14.09 / 11.88
11.89 / 11.81
04/20/23 NASA-JSC and DIAS 12
Table 4: A comparison of radiation quantities measured with JSC-TEPC and CR-39
(Fading correction applied to CR-39,ICRP60)
Space Mission
Absorbed
Dose
(TEPC / CR-39)
Dose Equivalent
(TEPC / CR-39)
Q
Factor
(TEPC / CR-39)
(µGy/d) (µSv/d)
Expedition 12 31.70 31.39 346.56 / 348.18 10.93 / 11.09
Expedition 13 31.31 / 30.54 356.58 / 359.97 11.39 / 11.79
Matroshka-2 (R2) ~ 34 / 33.08 ~ 390 / 388.39 11.47 / 11.74
04/20/23 NASA-JSC and DIAS 13
Charge Identification (G-Seff Method)For two points separated by x and with etch rate VT1 and VT2, G and Seff are:
Seff = Veff / Vg
Where Vg is the bulk etch rate and Veff, the effective etch rate is
For a track with 2n equally spaced etched cone, the overall value of G is given by:
And the overall value of Veff is
xVV
VVG
TT
TT
)(
)(2
12
12
21
212
TT
TTeff VV
VVV
n
ii
n
iiiiniiin
w
xVVwVVG
1
11212 /2
n
iiniini
eff
VVVV
nV
11212 2/
04/20/23 NASA-JSC and DIAS 14
Figure: Charge identification with G-Seff method for test events.
04/20/23 NASA-JSC and DIAS 15
We wish to thank all those who assisted us in the ISS, Matroshka and Dobies space missions.
DIAS wishes to thank the ESA PRODEX office for support of this work .