2003 Fiscal Year Final Research Report Summary
Construction of a non-destructive evaluation system of materials in use by using positrons
| Project/Area Number |
14350370
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Structural/Functional materials
|
|---|
| Research Institution | Osaka University |
|---|
Principal Investigator |
SHIRAI Yasuharu Osaka University, Graduate School of Engineering, Professor (20154354)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
ARAKI Hideki Osaka University, Graduate School of Engineering, Associate Professor (20202749)
MIZUNO Masataka Osaka University, Graduate School of Engineering, Assistant Professor (50324801)
|
|---|
| Project Period (FY) |
2002 – 2003
|
| Keywords | Positron Annihilation / Nondestructive Inspection / Lattice Defect / Fatigue / Materials Evaluation / Structural Materials / Metal / 格子欠陥 |
|---|
| Research Abstract |
Conventional positron spectroscopy methods suffered from certain limitations. For example, in-situ positron lifetime measurement is almost impossible at high temperature except for very limited cases. Another shortcoming is the practical difficulty to use positron annihilation as a nondestructive testing technique for the evaluation of materials.
The most essential method to resolve the limitations mentioned above is to separate the positron source from the specimen in order to keep the source in a mild environment at all times while the sample can be exposed, to any extreme conditions with no risk of radioactive contamination. On the other hand, the 1.28MeV photon which is emitted from _<22>Na positron source just after a positron emission, can no longer be used as the start signal for the lifetime measurement as it is hard to assure that a 0.511MeV photon detected by the stop detector originated from the same positron that emitted the 1.28MeV photon detected by the start detector. The
… More
β^+>-γ coincidence technique, in which the start signal is given by a positron that has passed through the start detector, is well-suited to separate source/sample geometry.
A new β^<+>-γ coincidence positron-lifetime spectrometer has been developed in order to expand the field of applications of positron annihilation. The adoption of a silicon avalanche diode as the start detector instead of a conventional photomultiplier tube equipped with a fast scintillator has been attempted as a step closer to the realization of a portable positron-lifetime spectrometer enabling on-site nondestructive evaluations of materials. On the other hand, the incorporation of an electromagnetic lens for positron-energy selection now allows for in-situ measurement at high temperatures with a desk-top positron lifetime spectrometer.
Improved designs of positron annihilation spectrometers extend the applicability of positron annihilation to in-situ high temperature measurement and to on-site nondestructive evaluation of materials. Defects and their properties will be clarified in many important or potential materials at high temperatures. Such information will be quite useful to develop materials and their processing. On the other hand, portable nondestructive tester of materials with a small positron sensor will soon appear. Less
|
Research Products
(11 results)
