Microscopic radiation quantities

Radiological Research Laboratory, Dept, of Radiology, Columbia University, New York.

Abstract

The physical quantities ordinarily used in relation to ionizing radiation are macroscopic in that they represent averages over large numbers of particles and absorption events. However, many radiation effects and in particular cellular radiobiological effects are often due to the action of very few particles and frequently only due to one particle. Under these conditions the microscopic quantities which specify the energy concentrations actually existing can differ greatly from their macroscopic counterparts.

Among possible microscopic quantities the local energy density and the event size are defined and their inter-relation is discussed.

Brief reference is made to experimental determinations of event size distributions with walled and wall-less proportional counters.

A number of ways are considered in which microdosimetric quantities can be employed in theoretical radiobiology.