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.