Glass technology has developed quicker and less costly techniques in sealing and vacuum processing which result in improved lamps and bulbs, thus producing a less costly and more reliable instrument package

Bergen, G.

English

NASA Technical Reports Server

1972	 B72-10132 
NASA TECH BRIEF 
Goddard Space Flight Center 
NASA Tech Briefs announce now 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 National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Glass Technology Involved in the Manufacture
of Magnetometer Components 
F- ]
The problem: 
The present glass technology for magnetometer source 
lamp and absorption cell fabrication requires involved 
vacuum processing and has problems in sealing pro-
cedures. 
The solution: 
New glass technology has developed quicker and less 
costly techniques in sealing and vacuum processing which 
result in improved lamps and bulbs. These, in turn, pro-
duce a less costly and more reliable instrument package. 
How it's done: 
The 1 cm diameter light source bulbs are made from 
Corning 7740 Pyrex glass. Bulbs of smaller diameter were 
found to have measurably shorter operating life times; 
due, probably, to diffusion of the inert gas into the glass. 
The bulbs are fabricated by splicing a 7 mm o.d. tube to 
a 3 mm o.d. tube. The tubes are cleaned thoroughly, 
soaked in a dichromate solution for 12 hours, and rinsed 
with distilled water. The tube is then set in a precision 
glassblowing lathe and heated at the 3 mm end to close 
the tube. A 1 cm bulb is then blown in the sealed end. 
The bulb is then flame annealed in an oven without 
forced air, cooled, and rinsed with pure ethyl alcohol. 
Fabrication of absorption cells presents the problem 
of sealing the lens on one end of the cell without dis-
tortion. The construction of the cell body and sealing 
the flat window are standard procedures. In sealing the 
lens, certain preparations and techniques are required. 
The lens is standard, but the lens edge is stepped 3 mm 
in from the inner edge. The mating end of the cell is 
beveled approximately 450 on the inside diameter to a 
feather edge to accommodate the lens. The lens and cell 
are aligned in the lathe and the sealing area preheated to 
a temperature to allow a very sharp flame to fuse the 
ass only where the lens and tube join. The configu-
ration results in the molten glass flowing only at the
feather edge allowing a permanent bond without en-
dangering the lens surface. The cell is then placed in an 
annealing oven preheated to 560°C (1040 0F). The end 
plate is normally sealed, and the cell is again oven 
annealed. 
Sealing of the bulbs or cells to the vacuum system is 
accomplished using a flow of thy nitrogen gas for clean-
liness and to prevent moisture from entering the system. 
A cesium ampule is sealed below the bake-out area and 
submerged in water to eliminate any metal migration 
during preliminary processing. The system is then rough 
pumped and checked for leaks. Next the diffusion pump 
is activated for the desired vacuum (2X10 7 mm Hg). 
The unit is then baked at 325°C for 24 hours. After 
cooling, the unit is surrounded by liquid nitrogen. The 
cesium ampule is broken, and the metal is distilled into 
the cells or bulb. When the desired amount of metal is 
collected in the unit, the diffusion pump is closed, and 
the unit is back filled with the buffer gas. When the re-
quired pressures are obtained, the units are tipped off 
and are ready for testing. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Goddard Space Flight Center 
Code 207.1 
Greenbelt, Maryland 20771 
Reference: TSP72- 10132 
Patent Status: 
This is the invention of a NASA employee and a patent 
application has been filed. Inquiries concerning license 
rights may be made directly to the inventor, Mr. George 
Bergen of Goddard Space Flight Center, Greenbelt, 
Maryland 20771.
Source: G. Bergen
Goddard Space Flight Center
(GSC-1 1283) 
Category 03 
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.
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Glass technology involved in the manufacture of magnetometer components

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