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Oral presentation

Development of gamma-ray induced positron age-momentum correlation measurements at UVSOR-III

Yamamoto, Ryohei*; Sugita, Kento*; Taira, Yoshitaka*; Hirade, Tetsuya

no journal, , 

Age-Momentum Correlation (AMOC) can observe the Doppler broadening of time-resolved annihilation gamma rays. The annihilation rate depends on the positron state, and it is possible to know if positrons are trapped in structural defects in a sample. Moreover, the Doppler broadening gives the information of impurities around the defects. Positrons from radioactive isotopes cannot penetrate a deep region of bulk material. The application of radioisotopes is difficult for the measurements under severe conditions such as in high pressure or a high temperature. Therefore, we have developed a GiAMOC (Gamma-ray induced AMOC) system, which is a measurement method for generating positrons in a sample using inverse Thomson scattered gamma rays in UVSOR-III. In addition, the developed measurement system was used to measure the reference material for positron lifetime measurement.

Oral presentation

Development of gamma-ray induced positron annihilation spectroscopy

Taira, Yoshitaka*; Sugita, Kento*; Okano, Yasuaki*; Fujimoto, Masaki*; Hirade, Tetsuya

no journal, , 

Positron annihilation spectroscopy is a powerful analytical method that can observe single-atom vacant defects in crystals and micro voids in insulating materials. UVSOR-III installed at the Institute of Molecular Science is promoting the development and user use of Gamma-ray induced positron annihilation spectroscopy (GiPAS) by ultrashort pulse gamma rays. Since the ultrashort pulse gamma rays generate positrons inside the material by pair production, positron annihilation experiments of bulk materials with a thickness of several cm can be performed non-destructively. We have succeeded in the generation of ultrashort pulse gamma rays and positron annihilation experiments such as the lifetime measurement and the positron age-momentum correlation measurement.

Oral presentation

Development of gamma ray-induced positron annihilation spectroscopy at UVSOR-III

Taira, Yoshitaka*; Sugita, Kento*; Yamamoto, Ryohei*; Okano, Yasuaki*; Hirade, Tetsuya

no journal, , 

We are developing gamma-ray-induced positron annihilation spectroscopy at UVSOR-III. This method enables defect analysis of the entire bulk sample with a thickness of several cm, which was difficult to measure with the conventional method using a positron radiation source. Currently, the user use of the positron lifetime measurement method is being developed, and in parallel with this, the coincidence Doppler broadening method, the age-momentum correlation measurement method, and the spin-polarized positron spectroscopy are being developed. Here, we will describe the development status of them.

Oral presentation

Development of polarimeter for circular polarization measurement of gamma-rays emitted from neutron capture reactions

Endo, Shunsuke; Abe, Ryota*; Ishizaki, Kohei*; Ito, Yuki*; Oku, Takayuki; Okudaira, Takuya*; Omer, M.; Kameda, Kento*; Kitaguchi, Masaaki*; Kimura, Atsushi; et al.

no journal, , 

no abstracts in English

Oral presentation

Development of gamma-ray induced positron annihilation spectroscopy

Taira, Yoshitaka*; Sugita, Kento*; Yamamoto, Ryohei*; Okano, Yasuaki*; Hirade, Tetsuya

no journal, , 

Positron annihilation spectroscopy is a powerful analytical method to observe single-atom vacant defects in crystals and microvoids in insulating materials. UVSOR-III installed at the Institute of Molecular Science promotes the development and user use of Gamma-ray induced positron annihilation spectroscopy (GiPAS) by ultrashort pulse gamma rays. Since the ultrashort pulse gamma rays generate positrons inside the material by pair production, positron annihilation experiments of bulk materials with a thickness of several cm can be performed non-destructively. In addition, since the sample is irradiated with gamma rays from the outside, measurement can be performed in an environment such as high temperature, high pressure, and immersion. We report on the generation of ultrashort pulse gamma rays and the development status of the positron lifetime measurement, and the positron age-momentum correlation measurement.

Oral presentation

Development of gamma-ray-induced positron age-momentum correlation measurement method in UVSOR-III

Yamamoto, Ryohei*; Taira, Yoshitaka*; Sugita, Kento*; Hirade, Tetsuya; Takashima, Yoshifumi*; Kato, Masahiro*

no journal, , 

Positron annihilation spectroscopy is a powerful analytical method that can observe single-atom vacant defects in crystals and microvoids in insulating materials. UVSOR-III installed at the Institute of Molecular Science is promoting the development and user use of Gamma-ray induced positron annihilation spectroscopy (GiPAS) by ultrashort pulse gamma rays. We have succeeded in positron lifetime measurement and lifetime momentum correlation measurement. This time, we succeeded in detecting the process of defect capture in the positron age-momentum correlation measurement of strained steel materials.

Oral presentation

Development of gamma ray induced positron annihilation spectroscopy

Taira, Yoshitaka*; Sugita, Kento*; Okano, Yasuaki*; Hirade, Tetsuya

no journal, , 

We applied the ultra-short pulsed gamma rays to positron annihilation spectroscopy (PAS). PAS using high energy gamma-rays, called gamma induced PAS (GiPAS), has several advantages compared with PAS using radioisotopes. (i) It enables defect analysis of thick material in a few centimetres because positrons are created throughout a bulk material via pair production by irradiation with gamma-rays having high penetration into the material. (ii) There is no contribution of positrons annihilated in the covering material of the shield sources, making the data analysis easy and accurate.

Oral presentation

Development of gamma ray-induced positron annihilation spectroscopy at UVSOR-III

Taira, Yoshitaka*; Sugita, Kento*; Okano, Yasuaki*; Hirade, Tetsuya

no journal, , 

Positron annihilation spectroscopy is a powerful analytical method that can measure vacant defects in crystals and microvoids in insulating materials. UVSOR-III is developing gamma-ray-induced positron annihilation spectroscopy using ultrashort pulse gamma rays. Specifically, we have succeeded in positron annihilation lifetime (PAL) measurement and positron age-momentum correlation (AMOC) measurement. PAL has succeeded in directly measuring the spectrum of only the sample. In addition, AMOC also succeeded in observing the positron annihilation only in the samples, which shows the different momentum distribution for the different defect states. At present, coincidence Doppler broadening (COB) measurement is also available, and a CDB spectrum with only positron annihilation from the sample will be obtained by the newly developed analysis program.

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