Which safety feature is critical to preventing radiation leaks in a camera's source assembly?

The safety stop ball is essential in preventing radiation leaks in a camera's source assembly. This feature acts as a mechanical barrier that ensures the radioactive source remains securely contained and cannot inadvertently be exposed. When the source is not in use, the safety stop ball effectively blocks the path, reducing the risk of accidental ionizing radiation emission.

In radiation safety practices, maintaining the integrity of source assemblies is crucial for protecting both the operator and the environment from radiation exposure. The safety stop ball provides a reliable means of ensuring that the source is fully contained when not actively in use, thereby mitigating potential hazards.

The other options, while important for specific functions in a camera system, do not directly address the containment of the radioactive source. For instance, aperture control influences the amount of light that can pass through the lens but does not relate to radiation containment. Similarly, an exposure timer manages how long the source is active but doesn't physically prevent leaks. Lastly, a power supply cutoff can halt the operation of the device but does not immediately secure the radioactive material, emphasizing the critical role of the safety stop ball in maintaining safety protocols.