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Many areas of scientific research require instruments that operate at temperatures of 77 K (-196 C) and below, usually referred to as cryogenic temperatures. Sometimes temperatures of 0.1 K or even lower are necessary. Current knowledge of the behaviour of materials at cryogenic temperatures is somewhat limited. There are many materials that would be likely to be of great use if the thermal and mechanical properties were better known. Even for supposedly well known materials, our knowledge is often based on a very limited set of measurements. Furthermore, these measurements were often made decades ago, at which time the composition of nominally identical alloys and polymers may have been sufficiently different to cause large differences in behaviour at low temperatures.

The usual solution to the lack of knowledge is to construct cryogenic instruments from a small number of materials with the best known properties. This can result in over-engineered instruments, a solution which can be acceptable for ground-based instruments but is a serious penalty for space-based instruments. Where it is not possible to use known materials, or if the demands are too critical to rely on existing knowledge, further measurements are required. The intial design is carried out with estimated values, with measurements then made in the hope that they will confirm the estimates. Due to tight time-scales, this often results in rushed experiments made in equipment which is not designed for this purpose, and the results can be of doubtful quality. Furthermore, while such an approach can be sensible for a small scale instrument, it is less appropriate for large instruments built over several years at a cost of tens of millions of pounds. Here, the impact in terms of money and delays is high if a material is discovered to be unsuitable, forcing a redesign and probably a new measurement programme on a replacement material. For the same reason, there is limited scope for innovative design. There is therefore a need for instrument development to be decoupled from research into materials and techniques for building such instruments. As instruments become larger and more complex, and resources more constrained, such an approach is becoming increasingly important.

Further information

Cryogenics: Cryogenic instruments in science.

Astronomy: Cryogenic instrumentation in astronomy.

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Page created: Adam Woodcraft
Last edited 2008-4-8     Site map
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