General problems on accurate determination of the absorbed dose

Various problems concerning the accurate determination of absorbed dose are described. Generally speaking, there are two kinds of the methods of practical measurements, the one is the absolute measurement and the other is the relative method. Three kinds of the method of absolute dose measurement can be considered. Those are the ionometric, calorimetric and chemical methods. Uncertainties of the measurement are affected by the condition of interest such as dose, dose rate and so on. The factors, which are important to make the uncertainties small, are presented and discussed in this paper. The correction factors for ion combination, humidity of air, impurity in gas and stem effect are important for the ionometry. In case of calorimetry, the important thing is that all of the absorbed energy do not usually appear as thermal energy and the so-called heat defect should be carefully inspected for the material and radiation under consideration. The G value in the chemical method is considerably affected by the LET value, and must be determined after the calibration in relation to other methods. In the practical methods of the absorbed dose measurements, it is necessary to make some pertinent calibration for detection devices. (Kato, T.)