"初级抽气泵" can be translated as "primary vacuum pump" or "elementary vacuum pump" in English, depending on the specific context and level of formality required.
"Primary vacuum pump" is a more common and technical term, often used in engineering and scientific contexts to refer to the first stage or main pump in a vacuum system.
"Elementary vacuum pump" is less commonly used but can convey the idea of a basic or entry-level pump, which might be more appropriate in certain educational or introductory contexts.
In most technical and professional settings, "primary vacuum pump" would be the preferred choice.