Vaporized tungsten on the glass envelope can cause loss of anode rotation and heat transfer problems to a cold anode. This is best described as:

• A. Bremsstrahlung overload
• B. Glass envelope contamination
• C. Focal spot misalignment
• D. Vaporized tungsten deposition

Answer: (D)

Vaporized tungsten on the glass envelope forms a film that directly disrupts how the tube handles heat and electrical flow. When tungsten from the focal track condenses on the envelope, it can create arcing paths and a heat-transfer barrier. That combination can cause the anode to lose rotation (arcing/stator issues can stall the rotor) and it impairs efficient heat transfer to the anode, especially to a cold anode, leading to overheating problems. The description points to a specific mechanism—tungsten deposition on the envelope—rather than a general envelope contamination, focal-spot geometry issues, or excessive radiation output.