Generalization of the variance-covariance method for microdosimetric measurements. II. Formulae for varying dose-rate ratio in the detectors and synopsis of results.

The variance method of microdosimetric measurements has been used to obtain the dose average event size, y(d), of a radiation from a series of repeated measurements at equal doses. Since it is not always possible to repeat the same dose in multiple measurements, a generalization, the variance-covariance method, has supplanted the earlier technique. It utilizes a pair of synchronized detectors and permits the derivation of y(d) from a series of measurements with doses that are allowed to fluctuate. In the preceding article, the two methods were extended to permit also the derivation of the second and third moments, y2 and y3, of the event sizes. The present communication carries the extension further by deriving formulae that remain valid when the ratio of the doses in the two detectors is subject to slow changes; this extends the applicability of the twin detector method to situations in which the detector system moves in a nonuniform field, or in which there is movement of shielding or scattering material near the detectors.