Novel Calibration Apparatus with Low Pressure Leak Detection Limit of 10^-10Pa·m³/s

A novel calibration apparatus, with a low pressure-leak detection limit of 10^-10 Pa·m³/s, was developed in cumulative comparison method. The original work included the built-in molecular flow gas-sampler, 1 ml in volume, all-metal ultra-high vacuum (UHV) system and minimization of background interference. First, the ultrapure argon atmospheric pressure at the pressure-leak's downstream was increased to 100 kPa; next, after properly cumulating in a given gas-path, the leaked He trace-gas was released into the expansion chamber and filled through the gas-sampler into the quadrupole mass-spectrometer (QMS) analysis chamber, equipped with non-evaporable getter pump, and the time evolution of the He-ion currents of the test and well-defined reference gas-mixtures was measured with QMS and compared; finally, the leakage-rate of a pressure leak was calibrated. The results show that the newly-developed apparatus is capable of calibrating pressure leak in 10^-8~10^-10 Pa·m³/s range with a combined standard uncertainty below 7. 5%.