A high vacuum pump comprising an in-line connection on a single drive shaft of an axial turbomolecular compressor and a peripheral compressor where the pump provides better than 10-7 Pascal inlet when exhausting to atmosphere. The peripheral compressor has a two stage optimized Gaede design which encloses the impellers in a shroud reducing the top and bottom volume surrounding the impellers and providing a large separation pressure drop region between stages of said peripheral compressors to reduce axial leakage.
