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|Author(s):||James A. Fedchak; Dana R. Defibaugh;|
|Title:||Long-term stability of metal-envelope enclosed ionization gauges|
|Published:||December 01, 2012|
|Abstract:||Ionization vacuum gauges are used as secondary standards by calibration laboratories and as transfer standards in intercomparisons among metrology laboratories. A quantitative measurement of gauge stability with respect to the gauge calibration factor is critical for these applications. We report the long-term calibration stability of hot-filament metal-envelope enclosed ionization gauges based upon the analysis of repeat calibrations of nine gauges over a 15 year period. All of the gauges included in the study were of the same type: Bayard-Alpert type ionization gauges of an all-metal construction with an integral metal-envelope surrounding the hot-filament, grid, and collector. All were calibrated repeatedly at the National Institute of Standards and Technology (NIST) using the NIST high-vacuum standard, but are owned by organizations external to NIST. The gauges were removed from the high-vacuum standard after calibration, shipped back to the gauge-owner, and were returned to NIST at a later date (more than 1 year) for re-calibration. Gauge stability was determined using a pooled standard deviation (weighted root-mean-square average of individual gauge standard deviations) based on all calibration factors measured at NIST and was used to define the relative uncertainty component associated with long-term stability uLTS. We determined uLTS = 1.9 % (k = 1) for gauges operated with 4 mA of emission current, and uLTS = 2.8 % for gauges operated with 0.1 mA emission current.|
|Citation:||Journal of Vacuum Science and Technology A|
|Pages:||pp. 2449 - 2451|
|Keywords:||ionization gauge, calibration, stability, vacuum measurement, ion-gauge pumping speed|
|Research Areas:||Pressure & Vacuum, Gas Metrology, Calibrations (Thermodynamic)|
|DOI:||http://dx.doi.org/10.1016/j.measurement.2011.10.04 (Note: May link to a non-U.S. Government webpage)|