Cold cathode ionization gage in a stainless steel housing accurately measures high pressures. The penning effect is used with a high voltage discharge in the presence of a magnetic field for an ion current proportional to the gas pressure in the gage

Herzog, R.

Kreisman, W. S.

English

NASA Technical Reports Server

February 1966
	
Brief 66-10041 
NASA TECH BRIEF H 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Cold Cathode Ionization Gauge Has Rigid Metal Housing 
Cover
Cathode 
C 
""	
Support Insulator 
Anode 
Support Insulator 
Cathode 
Anode 
Cathode Washer 
Weld Lug 
Anode 
Conductor
_ 
Cathode Conductor
Cable End Seal
LA
Glass Extension 
Tubulatuon 
Envelope 
The problem: To design an ionization pressure gauge 
to accurately measure pressures to 10- 14 torr. Hot 
filament gauges suffer from contamination by chemi-
cally active gases that change cathode emissive prop-
erties and hence gauge sensitivity. Cold cathode gauges 
of the glass envelope type suffer helium permeation of 
the envelope walls that reduces gauge sensitivity and 
requires frequent bakeout, thus losing its usefulness 
for long-period monitoring. 
The solution: A cold cathode ionization gauge con-
tained in a stainless-steel housing. The Penning effect 
is used, employing a high-voltage discharge in the
presence of a magnetic field to produce an ion current 
proportional to gas pressure in the gauge. 
How it's done: The gauge is contained in a stainless-
steel housing consisting of an envelope, a cover, and a 
tube for attachment to the measured enclosure. Ceramic-
to-metal cable end seals provide vacuumtight connec-
tions to anode and cathode. The anode is compres-
sively held in the envelope by four support insulators 
that ride in the channel machined in the envelope side 
wall. A weld lug provides the electrical connection 
between anode and anode conductor. The cathode is 
held in place by two support insulators under com-
pression between the bottom of the envelope and the 
go (continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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cover, which has four projecting tugs on its underside 
to mechanically lock it to the envelope. A cathode 
washer press-fitted into the bottom of the cathode 
provides an electrical connection between cathode and 
cathode conductor. A glass extension of the tubulation 
is provided for convenience in connecting the gauge to a 
glass test system. A permanent cast magnet (not shown) 
attached pole pieces of low carbon steel surrounds the 
gauge tube and provides an axial magnetic field of about 
1,100 oersted along the tube. 
In operation, the gauge envelope is grounded, and a 
high voltage of the order of 3 to 6 kv is impressed on 
the anode. The cathode conductor is connected to a 
milliameter that responds to current changes on the 
surface of the cathode. These current changes are di-
rectly proportional to the density (particle population) 
of the gas being measured and, therefore, the pressure 
of the gas.
Notes: 
1. The use of a stainless-steel, rather than glass, en-
velope avoids the problem of electrically charged 
surfaces that distort the electric field within the gauge 
and produce inaccurate readings. 
2. This type gauge should be useful in industrial appli-
cations in the fields of metals, chemicals, food proc-
essing, cryogenics, thin-film devices, and in the oper-
ation of high-energy particle accelerators. 
Patent status: Title to this invention has been waived 
under the provisions of the National Aeronautics and 
Space Act (42 U.S.C. 2457 (f)), to GCA Technology, 
Inc., Bedford, Massachusetts. 
Source: W. S. Kreisman and R. Herzog of

GCA Technology, Inc., under contract

to Goddard Space Flight Center

(GSFC-445) 
Brief 66-10041	 Category 01


Cold cathode ionization gage has rigid metal housing

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