| 摘要 |
<p>A method of measuring a permeation efficiency of a barrier comprises:Â Â Â Â Â placing a test sample 23 in a first chamber 22; and providing a reference gas 46 to a second chamber 44 separated from the first by a barrier 66, which reference gas has a plurality of stable isotopes. An equilibrium quantity of particles of the at least one stable isotope is maintained. Mass spectrometer readings in relation to the at least one stable isotope and the permeate are obtained, and correlated with the maintained quantity of at least one stable isotope particles, to obtain an absolute value for a quantity of the permeate, to establish a quantity of permeate passing through the barrier per unit time. The method may overcome problems associated with drift. A method of achieving a selected pressure in a chamber comprises providing the chamber with a first gas at a first pressure through an orifice plate with a first conductance C1, the diameter being selected to achieve molecular flow. The speed and conductance C2 of a pump 47 are adjusted to achieve molecular flow, and the first pressure and first and second conductance are adjusted to establish and maintain the selected pressure.</p> |
