The big freeze

From frozen fish fingers to stem cell storage, cryogenics is used in more applications than you might think - but whatever you do, don’t ask a cryogenic technologist to freeze a body part!

Cryogenic technology got a pat on the back from the Government recently. In the final of a competition for the new National Cluster Mark – which recognises the merits of competitive industrial concentrations – Ian Lucas (a former minister for Business) commended the Cryogenics Cluster for its achievements to date, and remarked on its growth potential. Centred at the Harwell Science and Innovation Campus, it had already won the South East regional stage of the competition.

Cryogenics is the production and maintenance of low temperatures, and the techniques are found in a surprising number of areas – scientific, medical and energy. In the South East of England there are a large number of organisations and companies engaged in low temperature research, development and manufacture.

The concentration of this activity in South East England is tangible from just the sight of trucks delivering liquid helium to the magnet makers in the area. And around the core of this manufacturing hub lies a unique network of supporting specialist cryogenic activity, from the industrial gas companies, to manufacturers of cryogenic transfer lines, even to warehouses equipped with helium connections. Unlike clusters of aerospace or biotech activity which can be found in other parts of the world too, this is a special concentration of hard-to-find expertise, unmatched anywhere else on earth. Interacting with this core of activity is an array of institutions, including the Science and Technology Facilities Council’s (STFC) Rutherford Appleton Laboratories at Harwell, the universities in Oxford and Southampton, and Research Laboratories in Culham. Much science involves low temperature, so cryogenics features prominently in the labs, be it in bombarding targets with neutrons, developing power from fusion, or putting instruments in space. MRI scanning is another major achievement. Without cryogenics to cool superconducting magnets to 4K, it couldn’t happen.

Liquid helium is the cryogen favoured for much science, for its low boiling point (4K) and high specific heat. The workhorse for much of industry meanwhile is liquid nitrogen (boiling at 77K or -196°C), which is cheap and available literally by the truckload. Less widely reported than the credit crunch, there has nevertheless been something of a helium crunch in recent times, with sharply escalating price, and even interruptions in supply on occasion too. This has caused something of a one-time stampede in low temperature laboratory equipment, away from using wet, liquid cryogens, in favour of dry, ‘cryocooled’ equipment. For the scientist, the attraction of avoiding the need to meet health and safety constraints arising out of using liquid cryogens, and the reduction in technician support required to ‘feed and water’ the machinery, makes a compelling never-go-back case. There can be the added attraction of no longer receiving a monthly bill for cryogens too – someone else often gets the bill for the electricity consumed by the cryocooler!

Cryocoolers are mechanical refrigerators that produce low temperatures. Small cryocoolers have been developed specifically for applications in space where they are used to cool sensitive detectors to low temperatures. The instruments have been used to monitor sea surface temperature, and the climate and pollutants in the upper atmosphere. For astronomy they have been used on the recent Planck spacecraft which is conducting a survey of the remnants of the ‘Big Bang.’ There are many types of cryocooler used to achieve low temperatures and the engineering of these requires a multi-disciplinary approach.

Cryogenics is a ubiquitous, enabling technology found everywhere from freezing fish fingers to storing stem cells. As such, there can be a danger of it being taken for granted. Safety considerations remain important – they include the dangers of asphyxiation in confined spaces from vapourising cryogens, and the need to manage potential pressure increase in the event of trapped volumes of liquid. A rare reference work is the Cryogenic Safety Manual available from the British Cryogenics Council (in hard copy, or now on CD too).

“Much science involves low temperature, so cryogenics features prominently in the labs, be it in bombarding targets with neutrons, developing power from fusion, or putting instruments in space”

Ubiquitous it may be, but in contrast to the oil and gas industry, most cryogenic engineering has not yet been committed to codes and standards. Design of thermal links is the subject of a variety of custom and opinion, while in the field of multi-layer insulation; technical sins are regrettably committed in practice every day. This may be about to change. Technologists at STFC’s sites in Oxfordshire, Cheshire and Edinburgh have embarked on developing new design guidelines, drawing on data from extensive testing, which will be made available to industry. The British Cryogenics Council has also gained permission to re-publish the highly regarded ‘Goodall Chart’ of cryogenic data which is found on many a laboratory wall around the world.

One use of cryogenic technology which is guaranteed to raise the ire (or bemusement) of ‘proper’ cryogenic technologists is the practice of freezing part or whole human bodies – in the hope that ‘something will turn up,’ by way of developments to restore life where it has previously expired. Sadly perhaps, while considerable sums of money change hands for such services, there is no sound, supporting science. The serious cryogenics profession is so keen to be distanced from this activity that it has given this activity a distinct name of its own – cryonics.  Never to be confused again with cryogenics!

“Cryogenics is a ubiquitous, enabling technology found everywhere from freezing fish fingers to storing stem cells”

It was in 1911 that discovery took place of the superconducting phenomenon which ultimately led to MRI scanning. So-called high temperature superconductors (still needing to be cooled to around liquid nitrogen temperature, but not as low as liquid helium) were discovered in 1986. Since these materials are essentially ceramic, the challenge of successfully manufacturing a conductor in the desired lengths at acceptable cost has exercised many a mind over the last 25 years – the solution looks more like tape than wire, using semiconductor manufacturing techniques rather than wire drawing – but the pace of development is such that it will not take a century for the next industry segments to emerge, exploiting the merits of these new superconductors. By way of example, the weight of wind turbine generators on top of their supporting pylons can be cut in half, helping reduce the cost of offshore wind power generation by a quarter. If magnets for laboratories and MRI were the first superconducting industry, perhaps superconducting wind turbines could be the next big market segment. Like MRI however, this can only be the case with soundly engineered cryogenic cooling systems in place to enable the superconductors to deliver their extraordinary performance.

To provide the cryogenic community with a forum to meet, exchange knowledge and display new product, building on the recognition conferred by the recent government competition, a Cryogenic Cluster Day is was inaugurated at STFC’s Rutherford Appleton Laboratory, Oxfordshire on September 22. The mix of seminar, table-top exhibit and science facility tour could become an annual fixture in the cryogenic calendar from 2010 forwards.