Microdosimetry at Middle Age: Some Old Experimental Problems and New Aspirations

The increasingly wider use of microdosimetry in fields other than pure radiobiological research, especially in "practical" domains such as radiation protection and medical physics, has created a number of new practitioners who are not fully acquainted with many of the experimental pitfalls which beset the aspiring microdosimetrist. This paper attempts to review some of the lesser known experimental obstacles. It also presents first results of measurements of single-event spectra at nanometer site sizes, based on the use of a small (0.5 x 0.5 mm) counter. Some observations and a critique of the operation of this counter are also presented. It is shown that the counter produces spectra at 5 nm which can be compared with theoretical predictions grounded on fundamental avalanche theory for a cylindrical counter.