Factors of Merit for Radiation Detectors*

Abstract

In Part I, the need for a suitably defined factor of merit for comparing the sensitivity of different radiation detectors is explained (Section 1). Both the advantages and the very important limitations of such a factor of merit are discussed.In Section 2, separate factors of merit for Type I and Type II detectors are defined. The factor of merit for Type I detectors is defined as the ratio of the noise equivalent power given by the fundamental limit defined in Paper I to the noise equivalent power actually measured in the reference condition. The factor of merit for Type II detectors is similarly defined in terms of the actual noise equivalent power in the reference condition and the empirically determined minimum value for the noise equivalent power proposed by R. J. Havens. Section 3 contains a brief discussion of the significance of the factor of merit for the special case of the bolometer.In Part II, the noise equivalent power in the reference condition, and the factor of merit is determined for about fifty thermocouples and bolometers. The results are presented in Tables I and II, and in Figs. 1 and 2. A description of each detector is given in Section 5, along with a statement of any special calculations which were necessary.All of the results presented are based on measurements made by other persons; no measurements were performed by the writer. The sources of information are described in Section 3.An Appendix is provided whose purpose is to call attention to the wide variety of possibilities in the specification of the relevant properties of radiation detectors, and thereby to encourage precision in the statement of these properties in the future periodical literature.