| 摘要 |
An improved vacuum system for a system for accurately tracing on an electron sensitive film with an electron beam which passes through three (3) adjacent vacuum stages and where each stage has a predetermined vacuum level is disclosed herein. The vacuum system is a high performance, fully automatic, three (3) stage, differentially pumped system. Two (2) stages of the system each use a diffusion pump as a first pump means. The diffusion pump of the second stage is backed by a single direct drive mechanical pump and also acts as the backing pump for the diffusion pump of the first stage. The third stage uses a single direct drive mechanical pump for vacuum pumping its chamber.
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