A model L40 American Time Products standard ambient temperature light chopper has been adapted to operate at liquid helium cooled temperatures. The application was in a 2−13 μ three−channel rocketborne infrared radiometer. The chopper tines were copper plated and indium gasket material was inserted between the adjoining tine mount surfaces. These two mechanical modifications, combined with the development of a high−efficiency, chopper−drive circuit, made the adaptation to operation at liquid helium temperatures complete. Locating the chopper in a focal plane away from the detector−preamplifier assembly made it possible to effectively eliminate chopper related capacitive, magnetic, and microphonic coherent noise.

Topics
Superfluids, Tuning forks, Amplifiers, Mechanical instruments, Geometrical optics, Optical instruments, Transition metals, Chemical elements
1.
W. L. Wolfe, Handbook of Military Infrared Technology (U.S.G.P.O., Washington, D.C., 1965), p. 759.
2.
C. L.
Wyatt
 and
R. H.
Haycock
,
Rev. Sci. Instrum.
45
,
434
(
1974
).
Google Scholar
Crossref
Search ADS
 
3.
M.
Harwit
,
J. R.
Houck
, and
K.
Ruhrmann
,
Appl. Opt.
8
,
475
(
1959
).
Google Scholar
 
4.
See Ref. 2.
5.
F. J.
Low
,
Proc. IEEE
54
,
482
(
1966
).
Google Scholar
Crossref
Search ADS
 
6.
Frank Dostal, Opt. Spectra 2, 29 (March/April 1968).
7.
M.
Harwit
,
J. R.
Houck
, and
K.
Ruhrmann
,
Appl. Optics
8
,
475
(
1959
).
Google Scholar
 
This content is only available via PDF.
© 1975 American Institute of Physics.
1975
American Institute of Physics
You do not currently have access to this content.