GAS PERMEABILITY EVALUATION DEVICE

PROBLEM TO BE SOLVED: To provide a gas permeability evaluation device capable of measuring gas permeability while performing air exhaustion from a mass spectrometric analysis chamber when the mass spectrometric analysis chamber is maintained at high vacuum even during sample replacing.SOLUTION: A gas permeability evaluation device 10 includes: a gas introduction chamber 1 for introducing gas; a front chamber 2 at the rear stage of the gas introduction chamber 1; and a mass spectrometric analysis chamber 3 at the rear stage of the front chamber 2. A substrate 5 is connected to a partition wall 4 for partitioning the gas introduction chamber 1 and the front chamber, a sample 20 is placed on an upper surface on the gas introduction chamber 1 side of the substrate 5, an orifice 7 becoming a diaphragm is provided in a partition wall 6 for partitioning the front chamber 2 and the mass spectrometric analysis chamber 3, a mass spectrometer 8 is connected to the mass spectrometric analysis chamber 3, and a vacuum pump for exhausting air from the mass spectrometric analysis chamber 3. From a gas permeation area A of the sample 20 and a conductance C of the orifice 7, a pressure measurement value pin the gas introduction chamber 1 and a pressure measurement value pin the front chamber 2, and a pressure measurement value pin the mass spectrometric analysis chamber 3 measured by the mass spectrometer 8, a gas permeability Jis evaluated from an expression: J=C(p-p)/A(p-p).