The name of international unit of irradiation dose is coulomb
per kilogram, indicated by C/Kg. The unit of absorption dose is
gray (Gy) which is equivalent to the radiation energy of
1 joule absorbed by 1 kilogram substance that is
1Gy == 1J/Kg.
Since 1930, the free-air ionization chamber has always
been used as the standard of irradiation dose. Its suitable
range of energy is 5-300 keV, suitable to be the irradiation
datum of quantity for 10-300 keV X-ray.
137
As regards the Y-rays of Cs and
60co, usually the
graphite-cavity ionization chamber is to serve as the datum of
quantity of irradiation dose.
Absorption dose is a physical measure of more practical
value. It is a physical measure suitable for any ray and substance,
unlike the irradiation dose suitable only to be used in X-ray,
Y-ray and the air.
At present, the competent methods for absolute measuring of
absorption dose are calorimetry, chemical method, and ionization
method.
The main absolute measuring methods used in absorption dose
for radiation processing are: calorimetry,
cerious sulphate-
P. 3
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