A glossary of Oxford Cryosystems terms
Cryogenics is the branch of science and engineering that deals with very low temperatures (below -150°C ), how to produce them and how materials behave in such conditions.
Crystallography is the science of the arrangement of atoms in solids. Many substances, from metals to proteins, can form crystalline structures – that is, with atoms arranged in regular patterns. And those structures can account for all kinds of unusual electronic, elastic or chemical properties. For example, protein crystallography is very important for developing new drugs and particularly relies on low temperatures, as protein crystals tend to decay rapidly when exposed to X-ray beams.
Gifford McMahon (GM) coolers
Like many other cooling devices, the original Oxford Cryosystems Cryostream relies on a supply of liquid nitrogen as the source of “cold”. As a result, it is not suitable for use in all working environments. A clever alternative technique, known as Gifford McMahon cooling, uses the expansion of pressurised helium gas to create a very cold surface (- 263°C). In our Cobra system, nitrogen gas extracted from the air (which is 79% nitrogen) can then be passed over this surface and rapidly cooled to an almost-liquid temperature.
In 2008, Oxford Cryosystems acquired the manufacturing rights for a range of Gifford McMahon coolers. Now, as well as incorporating these into our coolers for X-ray diffraction, the company manufactures GM systems in Oxfordshire for multiple uses worldwide. This growing part of the business looks as if it will be the next chapter in an exciting future for Oxford Cryosystems.
The temperature ranges of Oxford Cryosystems products are given in Kelvin (K for short), rather than degrees Celsius (centigrade) or Fahrenheit. This is because the Kelvin – named after the distinguished Victorian scientist, Lord Kelvin – is the unit that most scientists use to measure temperature. In fact, one Kelvin has exactly the same magnitude as one everyday degree Celsius. It’s just that the Kelvin scale starts in a different place, namely “absolute zero”, which is the coldest possible temperature: -273.16 ˚C or -459.67 ˚F. In other words: 0 K = – 273.16 ˚C. Most domestic freezers are set at around 255 K, but an Oxford Cryosystems PheniX can cool tiny samples right down to 12 K.
X-ray diffraction is a technique that has been fundamental in the development of several scientific fields. For example, it has revealed the structure and function of many biological molecules, including vitamins, drugs and – perhaps most famously – DNA. The technique is based on the Nobel-prize-winning discovery some 100 years ago that crystalline materials can cause a beam of X-rays to diffract in multiple directions. By measuring the angles and intensities of the diffracted beams, scientists can produce a 3D picture of the crystal’s structure. However, in order to get accurate results, the crystals have to be very cold indeed. Hence the need for Oxford Cryosystems devices.
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