| Popis: |
A new mass spectrometer with modulated molecular beam, designed primarily for combustion studies in systems of research and practical interest, was built. Based on relevant physical models, new expressions for the useful signals generated are derived and tested experimentally. Both effusive and viscous inflow is considered. In order to get a high signal-to-noise ratio and to minimize the background signal and noise a unique 3-chamber layout is introduced. The maximum sensitivity is dependent on the inlet configuration and differs between various species. For 16 0 17 0 at 13.3 kPa, 300 K with a flame inlet and an integration time of 1 s the sensitivity is estimated to 5 ppb. The corresponding sensitivity for water vapor after prolonged sampling of a flame, assuming a water mole fraction of 0.2 in the flame, is 6 ppm. A pulse counting technique allowing arbitrarily long integration times is used when higher sensitivity is needed. |
