Cold cathode ionization source generates smaller amounts of spurious gases and has a higher sensitivity than commonly used hot-filament ion sources. Photon and X-ray background noise are reduced below detectable levels

Roehrig, J.

Torney, F.

English

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April 1970	 Brie  70-1002 
NASA TECH BRIEF
_"W"	 4011111111111111 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
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be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Improved Magnetron Cold-Cathode Ion Source 
Auxiliary Cathodes 
The problem: 
The measurement of residual gases in an ultrahigh 
vacuum (. 10 9 torr) has become a problem of in-
creasing importance in vacuum instrumentation for 
basic research. While some improvements have been 
made recently in partial-pressure measuring instru-
ments ( mass spectrometers), t' o Fundamental prob-
lems still have not been adequately solved to satisfy 
present and future requirements. First, these mass 
spectrometers employ inherently low-sensitivity ioni-
zation sources of the hot-filament type. Sensitivity 
improvements are only possible at the output of the 
analyzer. Second, these sources produce undesired 
spectra of gases which are difficult to differentiate 
(continued overicuil 
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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from- the spectra of the gases in the system under 
study. This undesirable characteristic further reduces 
the effective sensitivity of the measurement. 
The solution: 
A cold-cathode ionization source was developed 
which generates smaller amounts of spurious gases 
and has 'a higher sensitivity than commonly used hot-
filament ion sources. 
How it's done: 
The ion source shown in the figure was designed to 
be fitted on a quadrupole analyzer. Based on the 
magnetron discharge, this ion source provides high 
sensitivity due to the long electron path inherent in 
the geometry of the source. Elimination of the hot 
filament normally used in the ion source reduces the 
amount of spurious gases generated within the spec-
trometer by removing the source of chemical and 
thermal activity. Photon and X-ray background noise 
are reduced below detectable levels by using an open 
ended cathode stub so that the amount of "cathode 
glow" detected by the electron multiplier is at a 
minimum.
Note: 
The following documentation may be obtained 
from:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: NA SA-C R-66793 (N69-30820), 
Program to Produce a Flight Prototype 
Cold Cathode Quadrupole Mass Spec-
trometer 
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 the Norton Research 
Corporation, 70 Memorial Drive, Cambridge, Mas-
sachusetts 02142. 
Source: Jonathan Roehrig and Franklin Torney of 
Norton Research Corp.
under contract to
Langley Research Center 
(LAR-10387)
. 
. 
. 
Brief 70-10023	 Category 02


Improved magnetron cold-cathode ion source

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