1. Sealed 22 Na source for positron 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

2. 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 Fukushima nuclear plant For inspection system

3. Sealed 22 Na radiation source currently in use Radiation sources on the market is requested to be sealed up safely in law. ⇒ 22 Na radiation sources act on materials like adhesives other than testing objects. This becomes a factor of measurement errors. Sealed 22 Na radiation source of IPL Inc. Part of adhesive ⇒ To achieve the PALS inspection handily in an arbitrary place, we developed and tested sealed 22 Na source not to mix adhesive. Effect of adhesive to lifetime histogram, RADIOISOTOPES, 55(8), 469-472 (2006)

4. Purpose of research Type 1: Kapton/ 22 Na/Kapton sealed sources of 60 kBq and 1 MBq. Type 2: Scintillator/ 22 Na/Kapton sealed sources of 1 MBq. Development of two types of high performance sealed 22 Na radiation sources free from the legal restriction of radiation handling Produced radiation sources sample kapton scintillator 22 Na Arrangement of Kapton film Type 1 Type 2 sample

5. 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 22 Na by Kapton film currently in use New way to seal 22 Na by Kapton film without contact with adhesive. The apparatus producing radiation sources is due to the idea proposed by professor T. Goworek of Maria Curie Skłodowska University (Poland). Type 1

6. POSK-22 made by IPL Inc. (  3 =1.45 ns, I 3 =2.6%) Type 1 radiation source (  3 =1.38 ns, I 3 =0.21%) A long life component of Type 1 has almost absent of POSK! Time/ns intensity/counts Type 1 (Kapton/ 22 Na/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 22 Na radiation source of 60 kBq manufactured for trial purpose Sealed 22 Na radiation source without positron annihilation in the adhesive was manufactured and tested. Sample : Si single crystal Type 1

7. Sample setting by sandwich manner 22 Na 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

8. Anti- coincidence PMT sample scintillator 22 Na 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 scintillator 22 Na Mirror PMT sample scintillator e+e+ e+e+ e+e+ e+e+ e+e+ e+e+ True signal Invalid signal remove not sample e+e+ e+e+ Type 2

9. Type2 (Scintillator/ 22 Na/Kapton) sealed source: A-C method Red ： Without A-C Blue ： With A-C Green ： Sandwich method (traditional) Time/ns Intensity/counts Experimental device of A-C method Configuration of detector （ 22 Na 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 scintillator 22 Na Background decreased to half Long life events were removed Sample : Si single crystal Type 2

10. Red ： Case 1 (I 2 =23.9%) Blue ： Case 2 (I 2 =11.4%) Kapton sealed 22 Na radiation source with scintillator Time/ns intensity/counts 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 kapton scintillator 22 Na Case1 Case2 Arrangement of Kapton film Kapton lifetime component decreases by deleting Kapton film in one side. Type2 Type1 Type 2

11.  detector Dark box DSO PC 22 Na/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 Intensity/counts Time/ns Normal system Development system Sample : Si single crystal Automatic measurement by program control from calibration to lifetime output ※ prototype

12. 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) Intensity/counts Time/ns Normal system Development system Sample : Si single crystal  detector Ti sealed source  + detector Positron detector for portable PALS (Ti sealed source for shading) ※ prototype

13. Summary  22 Na 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.

14. 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.