Dynamic extension - A new principle for a vacuum primary standard for UHV-range (10-10 Pa) calibration of hot cathode ionisation gauges |
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Authors: | L Peksa T GronychM Je?áb P ?epaM Vi?ar Z Krají?ekD Pra?ák F StaněkJ Tesa? |
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Affiliation: | a Charles University in Prague, Faculty of Mathematics and Physics, V Holešovi?kách 2, 180 00 Praha 8, Czech Republic b Czech Institute of Metrology, Okru?ní 31, 638 00 Brno, Czech Republic |
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Abstract: | The main obstacle in the construction of primary vacuum standards for very low pressures - ultra-high vacuum (UHV) - is outgassing from the walls of the apparatus. Thus, principles utilising a higher pumping rate in the calibration chamber, e.g., the pressure ratio technique, seem to be more useful for this range. However, a serious problem is inherent in this method, namely, that the gas in the calibration chamber is not in equilibrium and thus cannot be characterised by a single scalar pressure value, although such a value is then used to evaluate the measurement. This discrepancy can be overcome by using a hot cathode ionisation gauge as a transfer standard calibrated by the dynamic extension method.The dynamic extension method is explained and compared with the pressure ratio technique. The basic conditions for achieving acceptable uncertainty values are considered. |
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Keywords: | Primary vacuum standard Pressure ratio technique UHV calibration |
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