Using the modulating ion current gauge for total pressure measurements below 10−10 Torr without errors caused by electron-stimulated ion desorption

Total pressure measurements below 10−10 Torr, in an active residual gas, were made using a special hot-cathode ionization gauge, without errors caused by electron-stimulated ion desorption. The gauge can separate the two ion signals, i.e., the signal created from gas phase molecules and that from electron-stimulated ion desorption, by using a new modulation and amplification system. In order to verify this separation effect, experiments were made with oxygen and nitrogen introduction in the 10−10 Torr range.