A radiation detector having a sensitive area of Ad = 4 x 10-6 m2 is configured to receive radiation from a target area of diameter D1 = 40 mm when located a distance of L1 = 1 m from the target. For the experimental apparatus shown in the sketch we wish to determine the emitted radiation from a hot sample of diameter Ds = 20 mm. The temperature of the aluminum sample is Ts = 700 K and its emissivity is ?s = 0.1. A ring-shaped cold shield is provided to minimize the effect of radiation from outside the sample area, but within the target area. The sample and the shield are diffuse emitters.

(a) Assuming the shield is black, at what temperature, Tsh, should the shield be maintained so that its emitted radiation is 1 % of the total radiant power received by the detector?

(b) Subject to the parametric constraint that radiation emitted from the cold shield is 0.05, 1, or 1.5% of the total radiation received by the detector, plot the required cold shield temperature, Tsh , as a function of the sample emissivity for 0.05

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Radiation detector, A = 4 x 106 m? 4, -1 m Sample, T, = 700 K. 5 Cold shield, Tah e= 1 D, D,