# Solid Angle of Cylindrical Detector and Intrinsic Peak Efficiency

Find the solid angle subtended by the circular end surface of a cylindrical detector

(diameter of 10 cm) for a point source located 20 cm from the surface along the

cylindrical axis.

Also, assume that this detector has an intrinsic peak efficiency at 1 MeV of 12%. The

point source emits a 1 MeV gamma ray in 80% of its decays and has an activity of 20

kBq. Neglecting attenuation between the source and detector, calculate the number of

counts that will appear under the 1 MeV full-energy peak in the pulse height spectrum

from the detector over a 100 s count.

https://brainmass.com/physics/photons/solid-angle-cylindrical-detector-intrinsic-peak-efficiency-113336

#### Solution Summary

This solution contains an annotated diagram and also step-by-step calculations to determine the solid angle of the cylindrical detector using the appropriate cone formula. It also calculates the number of counts that will appear under 1 MeV full-energy peak with more than 100s a count. Brief explanations are included for further topic understanding.