Measurement of pressure differences between various positions in a vacuum chamber where pressure is generated dynamically

Abstract

The pressure differences between the positions for gauge connection in a chamber for gauge comparison were measured and evaluated in two ways: (a) by the mutual interchange of two ionization gauges at the positions; and (b) by readings of one ionization gauge at various positions and of a spinning rotor gauge at a fixed position. The pressure in the chamber was set up by simultaneous admission and pumping of the gas. Differences of the order of a few percent were observed, probably caused by imperfect adjustment of the gas-introducing jet. Those differences are specific to the given apparatus, they depend on its adjustment, the geometry and some other parameters. The two methods are suitable for checking and adjusting the apparatus.

Accurate measurement of pressure differences and the effect of baffle on pressure distribution in vacuum chamber during dynamic gas flow

“…5 shows the results of average generated pressure versus gas flow in the chamber with baffle (WB) and without baffle (WoB). It is clear from the figure that there is difference, though small, in pressures at location E of the chamber for both the cases, as recorded by CDG 3 E . The small variations in pressure at this position can be attributed to the location of this gauge which lies downward the inlet port and at the center of the chamber.…”

“…According to Jitschin and Reich [2], in common vacuum metrology the Maxwellian distribution can be applied for deriving pressures in the molecular regime with high accuracy. Pressure differences of the order of a few percent between various positions for gauges were also measured experimentally by Repa et al [3] and Peksa et al [4] in the pressure range from 10 À3 to 10 À1 Pa. They used a spinning rotor gauge (SRG) and two ionization gauges for the pressure measurements during their experiments.…”

A Study of Non-uniform Pressure Distribution in Vacuum Chamber during Dynamic Gas Flow

“…Under such circumstances, the pressure in the chamber is determined by the equilibrium between the gas flow in and the gas flow out. As regions of the chamber act as sources and sinks for the gas flow, a nonuniform distribution of pressure occurs over the whole chamber [3]. The term "non-uniformity of gas distribution" refers to the change of the flow, density and pressure values depending on the position in a vacuum system [4].…”

“…In [5], six reasons have been given for non-uniformity of gas distribution, which are: The effects of nonuniform gas distribution, likely to occur in practice, have been the subject of many recent detailed investigations [6]. P. Repa et al [3] have measured pressure differences of a few percent between various positions for gauges on a vacuum chamber in the range of 10 -3 -10 -1 Pa. Similarly, G.…”

Extending the Pressure Limit for Turbomolecular Pump up to 133 Pa by using Conductance-Reducer and Measuring the Pressure Differences in Vacuum Chamber

“…The pressure in the chamber is then determined by the equilibrium between the gas flow in and the gas flow out. As regions of the chamber act as sources and sinks for the gas flow, a non-uniform distribution of pressure occurs over the whole chamber [5]. Non-uniform gas distribution means specifically that if the gas characteristics at a point in a system are measured or established, these characteristics differ at other points in the system and such gas is often non-Maxwellian [6].…”