Cold cathode gauges for ultrahigh vacuum measurements

Nine cold cathode gauges have been evaluated on ion-pumped ultrahigh vacuum systems operating at pressures down to the 10(-11) Torr range. The test gauges included magnetrons, inverted magnetrons, and double inverted magnetrons from four different manufacturers as well as experimental variable-geometry gauges built especially for this project. Spinning-rotor and extractor gauges were used for calibration. The investigation covered repeated calibration over the 10(-10) to 10(-4) Torr range, stability over periods of up to 35 000 h of low pressure operation, tests for discontinuities in the current-pressure characteristics, stray magnetic field measurements, susceptibility to external magnetic fields, outgassing effects, and starting behavior at very low pressures. Our conclusion is that modern cold-cathode gauges are capable of giving far more accurate results than were possible with earlier Penning-type designs. Because of their extremely low outgassing rates, and their relative freedom from x-ray and electron stimulated desorption errors, they may in practice give results at low pressures which are more accurate than those obtained with typical hot-cathode gauges. (C) 1997 American Vacuum Society.