Dosimetry and yield

The dose is usually given in roentgens or in rad. The roentgen is a unit of exposure dose. It is the quantity of X- or 7-radiation such that the associated corpuscular emission per 0.001293 g of air produces, in air, ions carrying one e.s.u. of electricity of either sign. (0.001293 g of air is 1 cm3 of air at 760 torr pressure.) 

The value recommended by the International Commission on Radiological Units (1956) for the energy of ion pair formation in air is 34 eV. The energy dissipation per roentgen in 1 g of air is thus 88 ergs. The energy absorbed under the same conditions by a medium other than air can be calculated using the data in section 1.2. As an example, an exposure of 1 R corresponds to 97 erg g 1 absorbed in water, 95 in methylmethacrylate and 86 in carbon tetrachloride. 

The absorbed dose is usually given in rad, 1 rad corresponding to the absorption of 100 erg g-1. 

The conversion for the various energy units may be obtained from Table 3. 

The yield of a reaction induced by ionizing radiation is usually expressed in terms of a G value. The G value is the number of events produced per 100 eV absorbed in the system. The type of dosimeter used to measure the absorbed dose must be cited. 

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