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Paper VST-MoM4
Applicability of Spinning Rotor Gauges to Pressure Measurements in Sealed System

Monday, October 29, 2001, 10:40 am, Room 125

Session: Sealed and Insulating Vacuum Systems
Presenter: J. Setina, Institute of Metals and Technology, Slovenia
Authors: J. Setina, Institute of Metals and Technology, Slovenia
B. Erjavec, Institute of Metals and Technology, Slovenia
L. Belic, Institute of Metals and Technology, Slovenia
V. Nemanic, ITPO, Slovenia
Correspondent: Click to Email
Spinning rotor gauge (SRG) is truly inert vacuum gauge and has remarkable resolution and long term stability. Measuring element is a small steel ball, which is kept inside a measuring thimble, while all other necessary elements for the gauge operation are kept outside vacuum. The measuring head easily decouples from the ball/thimble assembly and the volume of the thimble is only few ml. All this makes the gauge especially usable for pressure measurement in sealed systems. However the accuracy of pressure measurements in a sealed systems is affected by the gauge residual drag. The residual drag changes whenever the suspension head is removed but remains stable during the continuos suspension if the ball. This makes gauge more suitable for studying pressure changes in a sealed system than for absolute pressure measurements. Pressure changes in a sealed-off device can be caused by leaks and permeation, outgassing or gas pumping effects. Through the years we successfully used SRGs for studies of gas pressure in different sealed-of devices. We will describe our experience of using SRGs for measurements in image intensifiers, miniature cathode ray tubes and recently in channel electron photomultipliers, flat vacuum insulation panels, ultrasensitive leak detection and studies of hydrogen outgassing from stainless steel. We will discuss how the unknown gas composition in the sealed system and the ball-thimble geometry influences accuracy of the gauge in the transition from molecular to viscous regime.