Sec. 1-1] 



MECHANICAL INPUT TRANSDUCERS 



21 



coefficient for different energy levels of the incident radiation and for 

 different absorbers is shown in Fig. (1-1)18. 



For a short summary and references on X-ray intensity and dose attenuation 

 for inhomogeneous X-ray radiation, see F. Kohlrausch, "Praktische Physik," 

 H. Ebert and E. Justi (eds.), vol. 2, no. 7.5112, Teubner Verlagsgesellschaft 

 m.b.H., Stuttgart, 1956. Also see M. D. Kamen, "Radioactive Tracers in 

 Biology," 2d ed., chap. 2, p. 61, Academic Press, Inc., New York, 1951. 



beta gauges. Isotopes commonly used in beta gauges together 

 with indications of their normal gauging ranges and of the maximum 



Table 3. Isotopes Used for Beta Gauges 



full-scale sensitivities obtained in commercial gauges 1 are tabulated 

 in Table 3 . The absorption of beta rays approximates an exponential 

 function over most of its range as ex- 

 pressed in Eq. (1). A representative 

 absorption characteristic is shown in 

 Fig. (1-1)19. The character of the curve 

 can change to some extent, depending 

 upon the geometry of the setup, the 

 energy and energy distribution of the 

 radiation, the kind of absorber, and 

 the detector used, i.e., ionization 

 chamber or electron counter. 2 



The mass absorption coefficient ///p 

 of any absorber for /3 rays is nearly 

 independent of the atomic weight of 

 the absorber and rises only slightly 



Thickness 



Fig. (1-1)19. Attenuation of beta 

 rays as a function of thickness of 

 the absorber. 



1 Values from Information Bulletin, Tracerlab, Inc., Waltham, Mass. 



2 For details on the attenuation of beta rays, see R. D. Evans, "The Atomic 

 Nucleus," chap. 21, McGraw-Hill Book Company, Inc., New York, 1955. 



