A cold shield is a device to protect an object from unwanted heating by
thermal radiation
Thermal radiation is electromagnetic radiation generated by the thermal motion of particles in matter. Thermal radiation is generated when heat from the movement of charges in the material (electrons and protons in common forms of matter) i ...
or light. Usually it is a cooled object with low absorption and high
reflectivity
The reflectance of the surface of a material is its effectiveness in Reflection (physics), reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the respon ...
.
It can be found in
molecular beam epitaxy
Molecular-beam epitaxy (MBE) is an epitaxy method for thin-film deposition of single crystals. MBE is widely used in the manufacture of semiconductor devices, including transistors, and it is considered one of the fundamental tools for the devel ...
chambers to protect the growth areas from thermal radiation from hot sources. In
cryostat
A cryostat (from ''cryo'' meaning cold and ''stat'' meaning stable) is a device used to maintain low cryogenic temperatures of samples or devices mounted within the cryostat. Low temperatures may be maintained within a cryostat by using various r ...
s, a radiation shield protects a sample from
infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
radiation. An
infrared detector
An infrared detector is a detector that reacts to infrared (IR) radiation. The two main types of detectors are thermal and photonic (photodetectors).
The thermal effects of the incident IR radiation can be followed through many temperature depen ...
is protected from thermal background radiation outside its optical
field of view
The field of view (FoV) is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation.
Human ...
. These devices are usually cooled to the same temperature as the detector.
Cold shields are typically used in IR optical devices for military, scientific and industrial applications to protect IR sensors from
stray IR radiation (lowering noise figures). Most cold shield applications require near instantaneous cooling, making low mass of the structure very important. Therefore,
electroforming
Electroforming is a metal forming process in which parts are fabricated through electrodeposition on a model, known in the industry as a mandrel. Conductive (metallic) mandrels are treated to create a mechanical parting layer, or are chemically p ...
is the preferred method of fabricating cold shields.
See also
*
Space sunshade
A space sunshade or sunshield is a parasol that diverts or otherwise reduces some of the Sun's radiation, preventing it from hitting a spacecraft or planet and thereby reducing its insolation, which results in reduced heating. Light can be di ...
References
* Cold radiation shields for IR detector arrays, N. Sclar, Infrared Physics, vol. 28, p. 173-176 (1988). ()
* , ''Methods of making infrared detector array cold shield''.
* {{US patent, 6091069, Ashley et al., July 18 2000, ''Infrared optical system''.
Infrared imaging
Thermal protection