FIG 17 is a schematic cross sectional diagram of a vacuum pump unit attached to the LPCVD apparatus of {HEAD ~ a ninth embodiment} of {TAIL ~ the present embodiment}, and FIG 18 is a graph illustrating output characteristics of a vacuum pump unit 
of
FIG 17 is a schematic cross sectional diagram of a vacuum pump unit attached to the LPCVD apparatus of { HEAD ~ a ninth embodiment } of { TAIL ~ the present embodiment } , and FIG 18 is a graph illustrating output characteristics of a vacuum pump unit
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