Bayard-Alpert gauge

The discovery of the x-ray effect spurred the development of a new generation of hot-cathode gauges designed to minimise this effect. One of the earhest, and commercially the most successful, the Bayard-Alpert gauge shown in Eigure 14b, was developed in 1950 (13). A fine wire, the ion collector, is... 

In practice, it is often necessary to take readings from hot-filament ionization gauges or other devices. Figure 5 gives pump-down curves for six different types of pumping equipment on the same vacuum chamber (23). The shape of curve 1 indicates that a real leak could be responsible for the zero slope demonstrated by the Bayard-Alpert gauge (BAG). The shape of the other curves could result from a combination of real and virtual leaks. 

Fig. 5. Plots of pump-down performance for pumps operating on 0.1-m-dia x 0.43-m-long stainless-steel tubing. Curves 1—4 are sputter-ion pumps of different makes curve 5 is Orbitron type and curve 6, LN-trapped oil DP. Pressure is measured using Bayard-Alpert gauge (BAG) (26). To convert Pa to...

Fig. 6. Bayard-Alpert gauge response vs time upon cutting off power to Orbitron pump (27). To convert Pa to torr, divide by 133.3.

Fig. 13. The introduction of a modulator electrode in a Bayard-Alpert gauge permits the pressure range to be lowered by a factor of 10 to 133 pPa...

Figure 2. Schematic view of the spectrometer. The components illustrated include M, crystal manipulator Q.M.S., quadrupole mass spectrometer I.G., primary ion source E.S., energy spectrometer G, Bayard-Alpert gauge T, crystal target and G.I., gas inlet. Auxiliary components are omitted for graphical clarity. The SIMS experimental geometry and coordinate systems are defined in the inset. Reproduced with permission from Ref. 4. Copyright 1981, American Institute of Physics.

In the gauge developed by Bayard and Alpert, Ix was decreased by reducing the surface area of the ion collector. In Bayard-Alpert gauges (BAGs), the collector is a thin wire surrounded by a cylindrical, coaxial open anode. With BAGs, pressures down to 10 9 mbar can be measured. 

A Bayard-Alpert gauge has a gauge constant for N2 of 17mbar 1. The emission current can be altered from 0.06 to 0.6 mA. 

Tungsten filaments can create large quantities of CO and C02 during operation, which may, or may not, affect your work. It is possible to obtain Bayard-Alpert gauges that can be preheated, or baked out, prior to use to limit this problem. 

The Bayard-Alpert gauge measures pressures down to 10 10 mm as shown in Fig. 2, the evolution of less than 1012 molecules occurring over... 

The potentials required for the operation of these gauges (Bayard-Alpert gauge anode +170 volts, cathode +25 volts, collector 0.5 volts Schulz-Phelps gauge anode +120 volts, cathode +60 volts,... 

Bayard-Alpert gauge (vacuum technology) A hot cathode ionization gauge using a fine-wire ion collector to minimize X-ray effects in the gauge. 

Bayard-Alpert gauge Bias active reactive evaporation Broad band antireflection Body-centered cubic (crystallography)... 

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