The present invention provides a vacuum apparatus that includes a plurality of
vacuum containers each having a gas inlet and an exhaust outlet, a gas supply system
for introducing a desired gas into each of the vacuum containers through the gas
inlet, and an exhaust system for keeping each of the vacuum containers at a low
pressure. In this vacuum apparatus, the exhaust system includes a plurality of
multistage vacuum pumps connected in series. The exhaust outlet pressure of the
last-stage vacuum pump is substantially at atmospheric pressure. The last-stage
vacuum pump is designed to exhaust gas from a plurality of vacuum pumps at previous stages.
