Gauge sensitivity

FIGURE 10.7 Air sparging pilot test showing portable compressor, airflow regulator meter/oil filter, and injection well layout (A), injection well with quick connect air line and pressure gauge (B), and observation well with magnihelic pressure gauge sensitive to 0.01-in. water column (C). 

Gas exposures are reported in units of Langmuir (1 Langmuir = 1 L = 1x10 torr-sec), uncorrected for ion gauge sensitivity and doser enhancement. Coverages, 0, are reported relative to the unreconstructed Au(lll) surface atom density (0 = 1 corresponds to 1.39x10 5 atoms/cm ). 

Gas adsorption is studied at pressures between 5 x 10 and 1 x 10 5 torr and at temperatures between 210 and 530 K. Surface structures are observed both with increasing exposure and after the gas is pumped away. Neither gas exposures nor background pressures are corrected for ion gauge sensitivity. 

The ionisation process does not reproduce, in the output of ions, the relative amount of gas at the source. By the use of reference gases, such as N2, the gauge sensitivity can be established and, by the use of appropriate correction factors, differing extents of ionisation can be accounted for. 

If f is now taken as the gauge sensitivity (= rate of change of manometer reading with respect to water transfer through cup), then... 

Ion gauge sensitivity varies with the exact geometry of the electrodes. The calibration for the two filaments of the same gauge may differ by 10%. On the other hand, the relative sensitivities for different gases appear independent of gauge structure the calibration need therefore be established for one gas only. Standardization is not at all simple (21, 104), The ratio ip/ie can be taken as linear in pressure only up to p 5 x 10-5 mm a high sensitivity McLeod gauge is therefore necessary for successful calibration. 

Table 6,2 Approximate ion gauge (Bayer-Alpert gauge) sensitivities (Sjc) relative to nitrt en, and ionization energies (IE), for some representative gases...

The analysis of dataset consistency is assisted by Lagrange multipliers, which gauge sensitivity of the consistency measure to the dataset uncertainties. The example is presented in Fig. 9. The two largest peaks are the sensitivities of the consistency measure with respect to the lower bound of the experimental uncertainty of dataset unit 57, and the upper bound Msg of the experimental uncertainty of dataset unit 58 (bottom left and right panels of Fig. 9, respectively). These same two dataset units surfaced in the pairwise test. Both facts gave us reason to suspect C/57 and/or f/sg as possible outliers. On reexamination of the original experimental data by the researchers involved (see Ref. [70]), errors in data recording were found and the corrections made were exactly in line with what the consistency analysis had indicated was probable. 

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