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X-ray and Positron Measurement GroupグループのHP

logoAtomic and nanoscale defects exert a large influence on the properties of advanced materials. Measurement of such defects is therefore of vital importance. Positrons can be used a sensitive probe of material defect characteristics. In our group, we use an electron accelerator to produce an intense, pulsed, variable energy, slow positron beam. Using this beam we are developing new techniques for characterization of advanced, functional materials. In addition, we are also developing next generation, intense positron beam production using a superconducting accelerator. Our expertise in accelerator technology has also led to the development of a transportable, high-energy X-ray imaging device. We are also involved with ion-beam technology and with the development of radiation detectors

Group's Research Theme

Fig.1:Positron probe microanalyze (PPMA)

Development of techniques for slow positron beam production and manipulation

In our group we have developed techniques for beam focussing and pulsing of an electron accelerator based intense slow positron beam. We have successfully measured 3-dimensional distributions of atomic defects in materials using a pulsed positron microbeam (the positron probe microanalyzer, PPMA). Using the PPMA we have also measured positron lifetimes under controlled atmospheric conditions by extracting the beam out of the vacuum through a thin window. In an effort to increase the slow positron beam intensity, we are also developing a superconducting accelerator for posiitron production.


Fig.2: 3-D distributions of atmic defects in ion irradiated sillica glass

as measured by a pulsed positron microbeam.

Measurement of atomic and nano-scale defects using positron beams.

Using a pulsed, slow positron beam we are characterizing atomic and nano-scale defects in metals, semi-conductors and polymers. In particular, by changing the energy of the beam the positorn pentration depth can be controlled from the near surface to a depth of around 1 micron. By performing variable energy positron annihilation lifetime spectroscopy (PALS) it is possible to characterize atomic defects in the surface region of thin films and layered materials etc.


Fig.3: X-ray tranmission image taken using a AA alkaline

battery operated X-ray source.

Development of compact, high-energy X-ray sources

Using a nano-structured carbon field emission electron gun, we are developing compact high-energy X-ray sources. The sources are battery operated (using standard AA batteries) and can generate short (ms) pulses of X-rays for X-ray transmission imaging. Using this technology, we are developing new instruments for on-site, non-destructive testing.

Staff Members

position & name field of expertise email address
Group Leader
Nagayasu OSHIMA
  email addressnagayasu-oshima[at]
Senior Researcher
Toshiyuki OHDAIRA
  email addresstoshiyuki-ohdaira[at]
Senior Researcher
O'Rourke Eugene Brian
  email addressbrian-orourke[at]
Senior Researcher
Koichi KINO
  email addresskoichi.kino[at]
Senior Researcher
Hidetoshii KATO
  email addresskatou-h[at]
  email addresskoji.michishio[at]

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