I am currently studying nuclear cross sections and this question considers the classic Rutherford scattering experiment. Here is a diagram of the experiment:
The detector is at right-angles to the source and since to keep things simple the solid angle coverage of the detector is 1 steradian.
My task is to calculate the number of $\alpha$-particles that are detected in an hour. I have calculated the differential cross section and was planning to multiply this by the exposure (which I'll change to per hour), the target density and the efficiency of the detector.
My lecturer tells me that I need to also multiply by the flux. My question is: how do I go about calculating the flux in this situation?
Any advice would be much appreciated, Sean.
N.B. Sorry for the wordiness of this post.