Which feature is NOT a function of the anode in an x-ray tube?

The function of the anode in an x-ray tube primarily involves supporting the rotating mechanism, acting as a thermal conductor to dissipate heat generated during x-ray production, and serving as an electrical conductor to facilitate the flow of electrons.

Mechanical support is essential because the anode needs to be robust enough to withstand the rotational forces during operation and provide stability to the x-ray tube. Thermal conduction is crucial since the process of x-ray production generates significant heat, and the anode helps transfer that heat away from the source to maintain optimal performance and prevent damage to the components.

Electrical conduction is also a key aspect of the anode's design, as it must effectively carry electrons from the cathode to facilitate the x-ray production process when high-voltage is applied.

The function of being an electrical insulator, however, does not align with the role of the anode. Insulation is necessary for parts of the x-ray tube that need to prevent the flow of electricity where it is not wanted, such as around the tube housing or areas that require separation of conductive components. Thus, the correct choice relates to a feature that is fundamentally outside the intended functions of the anode in its role in an x-ray tube.