Abstract :
The paper gives a brief review of the radiation and particle detectors used in modern nucleonic instruments and classifies the measuring systems used under four headings: (i) integrating systems; (ii) systems in which the mean current through the detector is measured, e.g. systems using current chambers, multiplying current chambers, etc.; (iii) counting systems; (iv) counting systems using an averaging circuit in the indicating unit, e.g. counting-rate meters. The paper includes a discussion of the long term stability of the radiation and particle detectors used in assay and other instruments and discusses the relative advantages and disadvantages of Geiger-Mÿller counters, proportional counters and scintillation counters from this point of view. Special consideration is given to the problem of industrial instrumentation where high reliabiityis the first consideration. The paper concludes with a description of a typical process control instrument developed at the Atomic Energy Research Establishment for the continuous monitoring of ¿-activities in solution and attention is directed to the precision of measurement possible under routine conditions.
