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Title: High vacuum measurements and calibrations, molecular flow fluid transient effects

Journal Article · · Vacuum
 [1];  [2]
  1. Savannah River Site (SRS), Aiken, SC (United States). Savannah River Nuclear Solutions.
  2. Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL).
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High vacuum pressure measurements and calibrations below 1 × 10-8 Torr are problematic. Specifically, measurement accuracies change drastically for vacuum gauges when pressures are suddenly lowered in vacuum systems. How can gauges perform like this? A brief system description is first required to answer this question. Calibrations were performed using a vacuum calibration chamber with attached vacuum gauges. To control chamber pressures, vacuum pumps decreased the chamber pressure while nitrogen tanks increased the chamber pressure. By balancing these opposing pressures, equilibrium in the chamber was maintained at selected set point pressures to perform calibrations. When pressures were suddenly decreased during set point adjustments, a sudden rush of gas from the chamber also caused a surge of gas from the gauges to decrease the pressures in those gauges. Gauge pressures did not return to equilibrium as fast as chamber pressures due to the sparse distribution of gas molecules in the system. This disparity in the rate of pressure changes caused the pressures in different gauges to be different than expected. This discovery was experimentally proven to show that different gauge designs return to equilibrium at different rates, and that gauge accuracies vary for different gauge designs due to fluid transients in molecular flow.

Research Organization:
Savannah River Site (SRS), Aiken, SC (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC09-08SR22470
OSTI ID:
1223188
Alternate ID(s):
OSTI ID: 1467497
Report Number(s):
VAC-D-15-00161; PII: S0042207X15001827
Journal Information:
Vacuum, Vol. 119, Issue C; ISSN 0042-207X
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 2 works
Citation information provided by
Web of Science

Figures / Tables (22)

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Table 3(p. 11)table Table 3
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Figure 10(p. 14)figure Figure 10
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Figure 11(p. 15)figure Figure 11
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Figure 13(p. 17)figure Figure 13
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Figure 18(p. 20)figure Figure 18
Table 4(p. 22)table Table 4

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