Step 1: Understand the geometry of the parabola.
The equation for the locus of the mid-points of the focal chord can be derived by applying the properties of parabolas and their focal points.
Step 2: Conclusion.
Thus, the correct equation is \( y^2 = 2a(x - a) \).
Final Answer:
\[
\boxed{y^2 = 2a(x - a)}
\]