Vacuum diffusion pump oil is mainly used in vacuum equipment and vacuum systems in laboratories, including scientific research, industrial production, medical equipment and other fields. The following are examples of some common countries where vacuum diffusion pump oil may be used:

United States: As an important country in the field of scientific research and industrial manufacturing, the United States uses vacuum technology in various applications, including semiconductor manufacturing, optical equipment, aerospace, etc. Therefore, vacuum diffusion pump oil is very common in the United States.

Germany: As an important country in the field of industrial technology, Germany widely uses vacuum technology in automobile manufacturing, chemical engineering, optics and other fields. Vacuum diffusion pump oil plays an important role in industrial production and R&D in Germany.

Japan: As a leading country in technological innovation, Japan widely uses vacuum technology in high-tech fields such as electronics, semiconductors, and optics. Vacuum diffusion pump oil is widely used in the electronics industry and research laboratories in Japan.

China: As one of the largest manufacturing countries in the world, China uses vacuum technology in many fields, such as semiconductor, photovoltaic, material science, etc. Vacuum diffusion pump oil plays an important role in China's industrial manufacturing and scientific research.

In addition, other developed countries and technologically advanced regions, such as South Korea, France, the United Kingdom, Switzerland, etc., will also use vacuum diffusion pump oil. The use of vacuum diffusion pump oil needs to be determined according to the specific needs and application fields of different countries and regions.