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Positron annihilation lifetime of irradiated polyimide Japan Atomic Energy Agency １ Graduate School of Ibaraki University ２ HIRADE, Tetsuya １、２ ; OKA, Toshitaka １ ; MORISHITA, Norio １ ; IDESAKI, Akira １ ; SHIMADA, Akihiko １ Trial of observation of free volume change of polyimide polymers with no Ps formation.
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Positron annihilation lifetime of irradiated polyimide
Japan Atomic Energy Agency １
Graduate School of Ibaraki University ２
HIRADE, Tetsuya １、２ ; OKA, Toshitaka １ ; MORISHITA, Norio １ ; IDESAKI, Akira １ ; SHIMADA,
Akihiko １
Trial of observation of free volume change of polyimide polymers with no Ps formation.
from Dupont web page
lifetime spectrum of kaptonco
unts
channel
1
10
100
1000
10000
100000
200 300 400 500 600 700 800 900
no Ps formation
No Ps Formation
Spur Reaction Model (by Mogensen)
M → M+ + e- Ionization
-R + e- → -R- electron scavenging
-S + e+ → [-S, e+] positron scavenging
####################### F I N A L R E S U L T S #######################
CONVERGENCE OBTAINED AFTER 10 ITERATIONSVARIANCE OF THE FIT = 1.085 WITH STANDARD DEVIATION 0.051CHI-SQUARE = 818.97 WITH 755 DEGREES OF FREEDOMSIGNIFICANCE OF IMPERFECT MODEL = 94.73 %------------------------------------------------------------------------RESOLUTION FUNCTION: G W S 1 0 1 FWHM (NS) : 0.1635 STD DEVIATIONS : 0.0005
INTENSITIES (%) : 100.0000
SHIFTS (NS) : 0.0000 STD DEVIATIONS : FIXED------------------------------------------------------------------------LIFETIME COMPONENTS: L T I 1 0 0 LIFETIMES (NS) : 0.3842 STD DEVIATIONS : 0.0004
INTENSITIES (%) : 100.0000 STD DEVIATIONS : 0.0000------------------------------------------------------------------------BACKGROUND: B 1 COUNTS/CHANNEL : 1.0340 STD DEVIATION : MEAN------------------------------------------------------------------------
λfree positron = λM + λF
λM:with the electrons on the chain positron trapped λF:with the electrons on the surrounding chains
Fig.1 Temperature dependence of positron annihilation lifetime in Kapton.
Positron annihilation lifetime of irradiated polyimide
Japan Atomic Energy Agency １
Graduate School of Ibaraki University ２
HIRADE, Tetsuya １、２ ; OKA, Toshitaka １ ; MORISHITA, Norio １ ; IDESAKI, Akira １ ; SHIMADA,
Akihiko １
Trial of observation of free volume change of polyimide polymers with no Ps formation.
1
10
100
1000
10000
100000
200 300 400 500 600 700 800 900
0200MGy
lifetime spectra of electron- irradiated kapton (8kGy/s)
coun
ts
channel
0
20
40
60
80
100
120
0 50 100 150 200 250
Elo
ngat
ion
(%)
0.377
0.378
0.379
0.380
0.381
0.382
0.383
0.384
0.385
0.386
0 50 100 150 200 250absorbed dose (MGy)
life
time
(
ns)
Observation of positron localizationDelayed Ps formation with trapped electrons
Polyethylene at 20kopen circle: in darknessfilled circle: under light
positron localization time : 70-80ps
N. Suzuki, T. Hirade, F. Saito, T. Hyodo, Radiation Physics and Chemistry, 68 (2003) 647-649T. Hirade, N. Suzuki, F. Saito, T. Hyodo, phys. stat. sol. (c) 4, No.10 (2007) 3714-3717
The intensity of ortho-Ps component in the lifetime spectra versus CCl4 concentration in n-hexane.
T. Hirade and O. E. Mogensen / Chemical Physics 170 (1993) 249-256
2
CCl4 concentration (M)
Conclusion
• Free positron annihilation lifetime might be able to give information of change of free volume of polymers, such as Kapton.
But "free positron" is not free!! We should understand positron chemistry !!
• Kapton lifetime for source correction for the lifetime analysis should not be obtained with no irradiated Kapton and might be about 378ps at room temperature.
Ďakujem !!
0.377
0.378
0.379
0.380
0.381
0.382
0.383
0.384
0.385
0.386
0 50 100 150 200 250absorbed dose (MGy)
life
time
(
ns) γirradiation
EB
