[Concept of the mean stopping power and the mean electron energy in electron dosimetry].

In consideration of the variations of the values E,Er,EH and Ew of the energy spectrum of electrons at the measuring point in case of a given energy on the surface Eo and in the depth t of a phantom with a low Z-number, the authors present the practical realisation of a conception allowing to determine by one single conversion curve Sw,1 (Er) the energy-dose of rapid electrons in water Dw, at least within the spectrum of Eo = 5 to 42 MeV and Er = 2.2 to 42 MeV, from the cavity ion dose Jc measured absolutely or by means of a calibrated electron chamber. Sw,1 (Er) is the relative unrestricted mass collision stopping power as a function of the mean rest energy Er at the measuring point. Er can be calculated in a simple manner from Eo and t and coincides almost perfectly with the most probable energy Ew of measured electron spectra. The authors present an algorithm for the calculation of the true mean electron energy E from Eo and t with a good coincidence with the values of measured electron spectra. It is shown that, contrary to the curve with one parameter Sw,1 (Er), a relation of Sw,1 to E leads to a series of curves with two parameters Sw,1 (Eo, t). The method using a relation of Sw,1 to Er which offers the advantage of a simple practical application and good precision is presented as "conception of the mean stopping power in electron dosimetry".