Setting the axis of the conical cavity at an angle to the axis of observation removes the imperfection at the apex of the cone from the direct observation area of the radiometer. Fillet no longer behaves as a nonuniformity in the blackbody

Schmidt, R. M.

English

NASA Technical Reports Server

December 1970	 Brief 70-10711 
S	 NASA TECH BRIEF 
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 National Technical Information Service, Springfield, 
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nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
An Improvement in Blackbody Cavity Design 
The problem: 
In the construction of conventional conical black-
body cavities, machining and coating the interior 
result in an unavoidable imperfection - a fillet at 
the apex of the cone. This fillet acts both as a 
nonuniformity in the radiance source and as a re-
flector of energy from the radiometer, causing per-
formance degradation, particularly when the cavity 
is used with a warm radiometer. 
The solution: 
.
	
	 Move the apex of the cone from direct view of 
the radiometer. 
How it's done: 
By setting the axis of the conical cavity at an angle 
to the axis of observation, the imperfection at the 
apex of the cone is removed from the direct observa-
tion area of the radiometer and no longer behaves 
as a nonuniformity in the blackbody.
Note: 
The following documentation may be obtained 
from:
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: 
NASA-CR-1583, Emittance Measurement 
Study 
Patent status: 
No patent action is contemplated by NASA 
Source: R. M. Schmidt of 
Honeywell, Inc. 
under contract to 
Langley Research Center 
(LAR-10292) 
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 ownedrights.
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An improvement in blackbody cavity design

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