Extending the Pressure Limit for Turbomolecular Pump up to 133 Pa by using Conductance-Reducer and Measuring the Pressure Differences in Vacuum Chamber

Abstract

A dynamic flow system has been developed which can be used for vacuum gauge calibration by comparison method-a calibration method in which the reading of the gauge under calibration is compared to another calibrated vacuum gauge called the "secondary standard"-and other vacuum-related experiments. The chamber of the calibration system is pumped by a turbomolecular pump (TMP), backed by a scroll pump. As maximum acceptable pressure at the inlet of a TMP is 0.1 Pa, above which the TMP decelerates, the pumping speed decreases and it becomes more difficult to adjust pressure under such circumstances. In the present work, high pressures of up to 133 Pa have been generated in the chamber of the newly developed dynamic flow control system by installing a well-designed conductance-reducer in the bypass line and, at the same time, operating the TMP in safe mode. In addition, the gas flow and pressure distribution within the chamber have been investigated for the entire pressure range (0.1 Pa ∼ 133 Pa) while generating pressure dynamically. Maximum deviations in pressure (1.6 %) were observed at point C on the chamber, which is close to the gas inlet port on the top of the chamber.