Positron annihilation technology:
Positron is the anti-
particle of electron. When shot into the material, the
positron combines with the electron therein and thus is
annihilated and emits two Y-photons. By measuring the energy and
exit-angles of these two Y-photons and the life-span of the
positron, what can be indicated include the electronic density in
the medium, electron-momentum longitudinal-component change, as
well as the information about the inner state and structure.
This method is a new-type probe of the microscopic structure
of material, capable of detecting the atomic fault, even one
or several atomic holes, which are imperceivable under electronic
microscopes. Its capacity includes: detecting the minute fault
on the broken section or surface of a work piece, such as the
wing of air-plane and the rotating axle; determining the
cavity in the material destruction; studying the ion compounds,
the impurity inclusion effect of semi-conductor; the phase-
change and crystallization in high polymer and non-crystalline
alloys; chemical reaction dynamics. In bio-medical science,
this technology can be used to quantitatively study the physio-
logical process, blood circulation, and the blood volume in
heart and brain. In the laminal scanning for diagnosing tumors,
this technology demonstrates a high sensitivity and precision
and no harm to human body. Therefore, this is a technology
with a great future in the field of medical science.
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