Problems of determining true equilibrium pressures of hydrogen getters over a wide range of getter temperature and hydrogen sorption

We have assessed a conventionally configured apparatus to measure hydrogen equilibrium pressures of getter alloys over the temperature range of 25 to 400 degrees C and hydrogen concentration range of 0.02 to 1 WA. An in situ approach has been proposed to correlate the measurements of different gauges using one of the precisely calibrated gauges as a standard reference. The pressure range of interest was 10(-7)-10(5) Pa and was covered using a Bayart-Alpert gauge, a spinning rotor gauge, and different capacitance gauges. The approach involves measuring the characteristic response of these instruments prior to determining hydrogen equilibrium pressures over the relevant range of wall and getter bed temperature. To evaluate the accuracy of the measurements, we performed an error propagation analysis. The use of a porous filter to avoid fines contamination and the adsorption/ desorption kinetics of the walls of the system were both addressed. (C) 1999 American Vacuum Society. [S0734-2101(99)04406-1].