What is the main advantage of the thoriated tungsten used in vacuum tubes?

• A. Increased thermal conductivity
• B. Reduced secondary emission
• C. Higher melting point and efficiency
• D. None of the above

Answer: (C)

Thoriated tungsten is primarily utilized in vacuum tubes due to its higher melting point and efficiency. Tungsten itself has a very high melting point, which makes it ideal for high-temperature applications found in vacuum tubes. The addition of thorium to tungsten increases the electron emission capability of the cathodes, enhancing the efficiency of the tube. This means that thoriated tungsten can emit electrons more readily at lower temperatures compared to pure tungsten, allowing for better performance under operating conditions.

The enhanced thermal stability that comes with thoriated tungsten also extends the life of the tube, reducing the likelihood of damage due to overheating. This characteristic is particularly valuable in applications requiring significant power and consistent operation, as it ensures the reliability and longevity of the vacuum tubes in use.