Answer:
Along the anode-cathode axis
Step-by-step explanation:
The Anode Heel Effect, in an X-ray tube states that the direction of emission of X-rays by the anode along the cathode-anode axis causes a variation in the intensity of X-rays.
The geometry of the anode causes the X-ray emitted perpendicular to the cathode-anode axis less intense than the X-rays emitted towards the cathode along the axis.