Double-wall vacuum chamber can be separated from the remainder of the system and pumped by ultra-clean techniques. Ultrahigh vacuum is maintained by the cryogenic effect of a cold wall and titanium chemisorption

Stephens, J. B.

Yager, S. P.

English

NASA Technical Reports Server

June 1970	 Brief 70-10130 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage corn rncrcLll 
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. 
Ultra-High Molecular Sink Vacuum Chamber 
Molsink Chamber 
The problem: 
To maintain an ultra-high vacuum, 10-12 torr, in 
a 10-ft vacuum chamber. 
The solution: 
A vacuum chamber has been designed with a guard 
vacuum surrounding the ultra-high vacuum chamber. 
Although the technique of incorporating the double-
wall chamber design in high vacuum operation is well 
known, this chamber has a novel feature in that the 
vacuum test chamber can be separated from the re-
mainder of the system and pumped by ultra-clean 
techniques. 
How it's done: 
The theory upon which the chamber is constructed 
and by which the ultra-high vacuum is maintained in 
the test chamber is best explained by an example. 
If a leak in the outer chamber allows one million 
molecules of a gas to leak into the guard vacuum and 
if there is a leak in the inner chamber which would 
allow molecules of gas to leak into the inner chamber 
and then 999,999 of those molecules would be evac-
uated from the guard vacuum by the pumps which 
are not shown, the other one molecule would leak 
into the test chamber and be evacuated there by the 
moltrap wall or by the titanium sublimator. Because 
it is relatively easy to evacuate one molecule of gas 
rather than one million molecules of gas, the ultra-
high vacuum may be maintained more easily in the 
test area by this procedure and by this construction. 
A pictorial representation of the chamber, with its 
salient features, is shown in the figure. The chambers 
are separated by a space, the guard vacuum, normally 
maintained at about 10 torr. The outer chamber is 
fabricated in two halves; the upper half contains a 
view port for observation during test operations. 
The inner chamber is fabricated in the form of a 
cylinder which has a bulkhead plate bolted to the 
top. The wall of the inner chamber is jacketed so that 
liquid nitrogen may be circulated through it. The 
vacuum inside the test volume is maintained at 10-13 
torr by the moltrap wall which is cooled to l0°K and 
coated	 it h titail iu iii by the sublimation pump. The 
continued overleaf) 
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ter 
amber 
all 
ard Vacuum 
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.
https://ntrs.nasa.gov/search.jsp?R=19700000126 2020-03-17T00:24:58+00:00Z
combined pumping action - the cryogenic effect of the 
cold wall and the titanium chemisorption - produce 
an ultra-high and ultra-clean vacuum. 
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: B70-10130
Patent status: 
No patent action is contemplated by NASA. 
Source: J. B. Stephens and S. P. Yager of 
Caltech /JPL 
under contract to 
NASA Pasadena Office 
(N P0-10799) 
Brief 70-10130	 Category 03


Ultra-high molecular sink vacuum chamber

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