Performance Study on Portable Calibration Apparatus of Mass Spectrometers for Partial Pressure

This paper tested part performance of the latest developed portable calibration apparatus of mass spectrometers for partial pressure. The ultimate vacuum of the device was measured using a reference ionization gauge; The diameter and the thickness of the gas-operated element which conductance is about 10⁻² m³/s could be measured accurately and the conductance was calculated using formular under the molecular flow condition. The conductance of the gas-intaked conductance elements with micro-meter apertures was measured using constant volume experiments. The back-streaming ratio is obtained using the same vacuum gauge to measure the gas pressure at both sides of the gas-operated conductance elements. The experimental results proved that the ultimate vacuum of the device is 4.8×10⁻⁷ Pa. The conductance of the gas-exhausted element for N₂ is 1.37×10⁻² m³/s. The conductance of two gas-intaked conductance elements for N₂ are 3.81×10⁻⁶ m³/s and 4.50×10⁻⁸ m³/s respectively. The back-streaming ratio for N₂ is 0.193 .Based on analysis, the calibration range of the device for N₂ is （4×10⁻²～5×10⁻⁶）Pa.