TNAG-1508-FCO40-2066-Guangdong-nuclear-power-station-project-at-Daya-Bay-safety-c-1987 — Page 50

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Back-scattering analysis and channel technology: When an

ion-beam bombards the nucleus of a sample, back-angle elastic

particles will result. Nuclei of different elements lead to

different amounts of energy carried by the particles being

reflected, thus the kinds of elements in the sample can be

distinguished. Moreover, bombarding ions would lose some

energy in the course of piercing into and reflecting out of the

sample. Therefore, difference appears in the particles reflected

from the identical element located at different depths.

means of this, the depth distribution of a certain element can

be detected. This method is suitable for the analysis of heavy

impurity elements in light host materials. If the bombarded

sample is a crystal and the ion-beam shoots in the direction

of the crystallographic axis, as if entering the "channel" in

the atomic arrangement, it will not come back. If the ion-beam

shoots in a direction deviating from the said crystallographic axis,

the ions would be catapulted back (i.e. back scattering). The

back-scattered particles change in line with the entering

direction. This phenomenon is called the channel back-scattering

technology. It is the most ideal method for detecting the radio-

active destruction of a sample and precise location of ion-atom.

This method finds its chief applications in solid physics,

material science, ion injection, thin-film growth, and surface

and depth analysis.

Accelerator mass-spectrographic analysis: the accelerator

is used as the mass-spectrometer, i.e. the sample to be tested

is put into the ionization source to be transformed into ions,

which undergo acceleration and electro-deflection, recorded

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