Hot-cathode ionization gages used to measure high-vacuum pressures are subject to error when ionizing radiation is present. Because this radiation creates additional ions, a second ion gage is mounted near the pressure-measuring gage to detect and measure the radiation induced error

Summers, R. L.

English

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Ion Gage 
Control
 
A 54--- 
.
B 
etector 
May 1969	 Brief 69-10156 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Vacuum Gage System for Radiation Environment 
Gage A
Pressure Measuring 
The problem: 
Hot-cathode ionization gages (or ion gages) used to 
measure high-vacuum pressures are subject to error 
when ionizing radiation is present. These gages use 
electrons emitted from a hot filament to ionize the 
gases present in the vacuum system. The ions are 
collected and the ratio of ion current-to-electron cur-
rent is used as a measure of the system pressure.. 
If another ionizing source (the radiation environ-
ment) is present, additional ions will be created. 
These additional ions will be collected along with the 
regular ion current, and the pressure indication will 
be in error.
The solution: 
A second ion gage is mounted near the pressure-
measuring gage to detect and measure the radiation 
induced error. 
How it's done: 
Two ionization gages are so mounted that they 
sense identical environments of pressure and radiation. 
Gage A (the pressure measuring gage) is wired in the 
conventional manner. The grid and filament of gage B 
(the detector gage) are connected to the grid and 
filament of gage A. Only one filament lead from gage 
B is connected so that the filament is not heated. The 
ion-collector leads are connected to the control unit 
(continued ovrIeaf) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000156 2020-03-16T17:56:58+00:00Z
through a switch so that the ion current from either 	 Notes: 
gage may be measured. 	 I. No further documentation is available. 
Gage A and the control unit continue to function 	 2. Technical questions may be directed to: 
in the normal manner. The collector-lead switch can	 Technology Utilization Officer 
then be used periodically to determine the radiation- 	 Lewis Research Center 
induced error. The output of gage B will also be 	 21000 Brookpark Road 
pressure units, so that the error from gage B can be 	 Cleveland, Ohio 44135 
directly subtracted from the output of gage A. 	 Reference: B69-10156 
Patent status: 
No patent action is contemplated by NASA. 
Source: Robert L. Summers 
(LEW-10797)
. 
Brief 69-10156	 Category 01


Vacuum gage system for radiation environment

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