Sealed 22Na source forpositron annihilation lifetime spectroscopy
AIST
M. Yamawaki, Y. Kobayashi, K. Ito
JRIA
M. Matsumoto, H. Ishizu, A. Umino
TOYO SEIKO Co., LTD.
K. Hattori, Y. Watanabe
The 10th International Workshop on Positron and Positronium Chemistry
Background of research
Nondestructive testing in site
http://www.toyoseiko.co.jp/product/product07.html
Shot peening device
http://www.toyoseiko.co.jp/product/product04.html
To improve the safety of the large-scale systems of the social infrastructure, material inspection techniques to assess the state of fatigue and to evaluate the shot peening performance of materials used for large-scale structures such as nuclear reactors and aircrafts have attracted considerable attention.
Usefulness of PALS (Positron Annihilation Lifetime Spectroscopy), which is basically one of nondestructive testing methods.
⇒
For Fukushim
a nuclear plant
For inspectio
n system
Sealed 22Na radiation source currently in use
Radiation sources on the market is requested to be sealed up safely in law. ⇒ 22Na radiation sources act on materials like adhesives other than testing objects. This becomes a factor of measurement errors.
Sealed 22Na radiation source of IPL Inc.
Part of adhesive
⇒ To achieve the PALS inspection handily in an arbitrary place, we developed and tested sealed 22Na source not to mix adhesive.
Effect of adhesive to lifetime histogram,RADIOISOTOPES, 55(8), 469-472 (2006)
Purpose of research
Type 1: Kapton/22Na/Kapton sealed sources of 60 kBq and 1 MBq.Type 2: Scintillator/22Na/Kapton sealed sources of 1 MBq.
Development of two types of high performance sealed 22Na radiation sources free from the legal restriction of radiation handling
Produced radiation sources
sample sample
kapton
kaptonkapton
scintillator
22Na
22Na
Arrangement of Kapton film
Type 1
Type 2sample
Production of Type 1 radiation source
It is supposed that in a traditional radiation source the adhesive reaches the radiation source during bonding of Kapton flims
The surrounding of the outside of Kapton films is bonded with the adhesive while suppressing around the radiation source with a cylindrical weight.
Traditional way to seal 22Na by Kapton film currently in use
New way to seal 22Na by Kapton film without contact with adhesive.
The apparatus producing radiation sources is due to the idea proposedby professor T. Goworek of Maria Curie Skłodowska University (Poland).
Type 1
POSK-22 made by IPL Inc.(3=1.45 ns, I3=2.6%)Type 1 radiation source(3=1.38 ns, I3=0.21%)
A long life component of Type 1 has almost absent of POSK!
Time/ns
inte
nsi
ty/c
oun
ts
Type 1 (Kapton/22Na/Kapton) sealed source
A long life component was mostly decreased by preventing the radiation source from being contaminated with the adhesive.
Production device to prevent the source from mixing with the adhesive
Sealed 22Na radiation source of 60 kBq manufactured for trial purpose
Sealed 22Na radiation source without positron annihilation in the adhesive was manufactured and tested.
Sample : Si single crystal
Type 1
Sample setting by sandwich manner
22Na source( sealed by Kapton film )
Sample (two boards)
Each sample is sandwiched by aluminum foil
Positrons emitted from the radiation source must be annihilated in the sample
Traditional PALS measurement needs the sample cut out from the object to be inspected.
Sample setting in usual PALS measurement
We propose the Anti-coincidence method, which does not need the cutting out sample.
Type 2
Anti-coincidence
PMT
PMT
PMT
sample
scintillator22Na
Mirror
PMT
Positron life time detector(conventional)
+ detector
(Additional circuit)
Anti-coincidence (A-C) method
※patent pending
PALS measurement method in which cutting out samples is not unnecessary
The event of the simultaneous detection is excluded from counting.
M. Yamawaki, Y. Kobayashi, K. Hattori, Y. Watanabe, JJAP, 50 (2011) 086301
The event of annihilation caused outside the sample area is removed
scintillator22Na
Mirror
PMT
sample
scintillator
e+e+e+
True signalTrue signal
Invalid signalInvalid signalremoveremove
not sample
e+
Type 2
Type2 (Scintillator/22Na/Kapton) sealed source: A-C method
Red : Without A-CBlue : With A-CGreen : Sandwich method (traditional)
Time/ns
Inte
nsi
ty/c
oun
ts
Experimental device of A-C method
Configuration of detector( 22Na is sandwiched by sample material and scintillator)
Invalid signals are deleted by A-C method !
With the A-C method, annihilation events in the scintillator, long life components not related with the sample (red dotted line), were removed invalid lifetime data.
Positron detector
PMT
sample
kapton
Al foil
scintillator22Na
Background decreased to halfLong life events were removed
Sample : Si single crystal
Type 2
Red : Case 1 (I2=23.9%)Blue : Case 2 (I2=11.4%)
Kapton sealed 22Na radiation source with scintillator
Time/ns
inte
nsi
ty/c
oun
ts
Kapton lifetime component was greatly decreased by putting the radiation source directly on the scintillator surface
Kapton sealed radiation source with scintillator
Production of radiation source
Decreased Kapton component
Sample : Si single crystal
sample sample
kapton
kaptonkapton
scintillator scintillator
22Na
22Na
Case1 Case2
Arrangement of Kapton film
Kapton lifetime component decreases by deleting Kapton film in one side.
Type2Type1
Type 2
detector
Dark box
DSO
PC
22Na/sample
+ detector
Development of PALS Inspection System
The commercialization of PALS inspection system aims to be achieved in two years.
Feature of system : No need of cutting out inspected materials : possible only to put sample on inspection stage
Inte
nsi
ty/c
oun
ts
Time/ns
Normal systemDevelopment system
Sample : Si single crystal
Automatic measurement by program control from
calibration to lifetime output
※prototype
Development of portable type System
The commercialization of PALS inspection system aims to be achieved in two years too.
Feature of system : Portable for large-scale structures inspection : Ti sealed source for shading (no need dark box)
Inte
nsi
ty/c
oun
ts
Time/ns
Normal systemDevelopment system
Sample : Si single crystal
detector
Ti sealed source
+ detector
Positron detector for portable PALS(Ti sealed source for shading)
※prototype
Summary
22Na sealed radiation source without the handling restriction was made for trial purpose and tested.
It was confirmed that the lifetime component due to the adhesive disappeared in the trial product.
It was confirmed that the sealed radiation source made for trial purposes was appropriate as the radiation source used for the anti-coincident method.
At the end of lecture
Thank you for listening
The present study is done under the consignment business of the supporting industry planned by Chubu Bureau of Economy,Trade and Industry in 2010 fiscal year. Moreover, the apparatus producing radiation sources is due to the idea proposed by professor T. Goworek of Maria Curie Skłodowska University (Poland). We wish to express our gratitude for his cooperation. And thank you for many advices from professor Mohamed F. Hamdy.