Slopes on semilog paper

Answer. For each element, E,(r) is given by a straight line on semilog paper (Equation 3.42) with intercept (E,)o and a negative slope of A,- (Figure 3.12). Adding the curves arithmetically gives E t) directly ... 

A measurement of the quantity A soo is obtained from a knowledge of the actual flux distribution in the test specimen. The usual experimental procedure is to obtain a measure of the relative flux at various stations along the axis of the parallelepiped by means of metallic foils. The activation of these foils due to neutron captures is directly proportional to the flux level at the foil. Thus a plot of the foil activities as a function of position along the axis will yield a curve having the spatial form of the axial thermal flux. Moreover, if this curve is drawn on semilog paper, it will display a linear behavior in the intermediate range AS, as shown in Fig. 5.266. The slope of this curve yields the quantity fcaoo. But, from (5.243) we have that... 

Using the data obtained by the procedures described in Section IV, make a plot of the spatial variation of the thermal-neutron flux as a function of distance from the front face of the diffusion box. The slope of the plot on semilog paper of the measured flux as a function of distance along the z direction yields the constant 7, from which L may be computed. If applicable, plot the transverse thermal-neutron flux from the appropriate data. Also, it may prove useful to compute and list the absolute flux as determined by a gold-foil irradiation along with the gold-cadmium ratio. 

Thus, by graphing the data on semilog graph paper and drawing a straight line through the data it is possible to read Cp° from the intercept and calculate kel from the natural log slope, as in Eq. (18) ... 

Thus, plotting In C vs. time on linear graph paper or C vs. time on semilog graph paper should produce a straight line, as shown in Figure 12.5. The slope provides a value for (Equation 12.5) and the intercept provides a value for D/V. With D known, V can be calculated by Equation 12.6. 

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