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Low Temperature Constructional Materials
Conference reports In the last session, new and developing applications were covered in six presentations. The first of these was on the design details and experimental evaluation of superconducting dipole magnet cryostats for the proposed Superconducting Super Collider high energy physics research facility, which will require one of the major cryogenic system undertakings of the next decade. The remaining presentations included the neutron-moderator system designed and successfully operated at Los Alamos, techniques for forming liquid and solid fuel layers in direct-drive laser fusion capsules, an evaluation of cryogenic propellant depot options for orbital transfer vehicles, a
consideration of closed-cycle helium refrigerators for recondensation of helium and nitrogen in mobile resonance imaging superconducting magnets, and the design, fabrication and testing of a complex beryllium cryostat for the temperature range 10--30 K.
M.J. Hiza Delta-MH, Inc., Boulder< Colorado, USA W.M. Haynes NBS, Boulder, Colorado, USA
Low Temperature Constructional Materials London, UK, 3 February 1987 A one day meeting entitled Low Temperature Constructional Materials was held at the Institute of Physics headquarters in Belgrave Square, London, on 3 February 1987. The meeting was sponsored by the Low Temperature Group of the Institute and co-sponsored by the Materials and Testing Group, The British Cryogenics Council and The Institute of Metals. There were 37 participants of whom approximately half were from industry. There were just eight presentations and this allowed the speakers adequate time to go into sufficient depth to be of interest without having to hurry unduly. Brian Hands (Oxford) set the scene by reminding the meeting which metallic materials are best suited to low temperature constructional work, and described their characteristics. He also reviewed low temperature joint techniques. David Evans (Rutherford and Appleton Laboratory) reviewed the use of resins at cryogenic temperatures and the factors governing the choice of resins for applications such as laminating and the impregnation of superconducting windings. One of the main messages to emerge was the need for improved measurements and standards in this area. A serious note was struck by Jim Currie (BOC) who outlined safety problems which arose through the wrong choice of materials in cryogenic engineering, including the loss of life in a series of accidents resulting from this. The most astonishing incident reported was a fatality caused by the ingestion of a small quantity of finely divided powder insulation which had been spilled. A very useful review of the low temperature thermal conductivity of polymers was presented by Dennis Greig (Leeds) who demonstrated that three distinct temperature
274 Cryogenics 1987 Vol 27 May
regions (T > 25K, 1K < T < 25K, T < 1K) are characteristic of this particular property of polymers. Bob Adams (Bristol) presented some interesting results on the dynamic properties of materials at low temperatures. These were concerned mainly with the damping and dynamic moduli of materials for use in cryoalternators. David Dew-Hughes (Oxford) provided food for thought by generating some question marks over the conventional view that austenitic steels make the best low temperature constructional materials when used in high magnetic fields. They can become highly magnetic for a variety of reasons. The message of this report was that more data is needed. An illuminating and detailed account of the construction of space-bound optical components, which are required to work at liquid helium temperatures for the ISO project, was given by T. Patrick (Mullard Space Science Laboratory). Finally Mike Priddey (Bunting Titanium Ltd) exploded a few myths about titanium. He demonstrated that it isn't as prohibitively expensive and difficult to use as is commonly thought and that its unique properties render it ideal for many cryogenic applications. He had an amusing theory that the reluctance of some people to use titanium may be because they associated its name with the Titanic! This was an excellent meeting with just the right number of participants and well presented papers to allow everybody to get the maximum out of the day. We could do with more like it.
H. Jones Clarendon Laboratory, University of Oxford, UK
consideration of closed-cycle helium refrigerators for recondensation of helium and nitrogen in mobile resonance imaging superconducting magnets, and the design, fabrication and testing of a complex beryllium cryostat for the temperature range 10--30 K.
M.J. Hiza Delta-MH, Inc., Boulder< Colorado, USA W.M. Haynes NBS, Boulder, Colorado, USA
Low Temperature Constructional Materials London, UK, 3 February 1987 A one day meeting entitled Low Temperature Constructional Materials was held at the Institute of Physics headquarters in Belgrave Square, London, on 3 February 1987. The meeting was sponsored by the Low Temperature Group of the Institute and co-sponsored by the Materials and Testing Group, The British Cryogenics Council and The Institute of Metals. There were 37 participants of whom approximately half were from industry. There were just eight presentations and this allowed the speakers adequate time to go into sufficient depth to be of interest without having to hurry unduly. Brian Hands (Oxford) set the scene by reminding the meeting which metallic materials are best suited to low temperature constructional work, and described their characteristics. He also reviewed low temperature joint techniques. David Evans (Rutherford and Appleton Laboratory) reviewed the use of resins at cryogenic temperatures and the factors governing the choice of resins for applications such as laminating and the impregnation of superconducting windings. One of the main messages to emerge was the need for improved measurements and standards in this area. A serious note was struck by Jim Currie (BOC) who outlined safety problems which arose through the wrong choice of materials in cryogenic engineering, including the loss of life in a series of accidents resulting from this. The most astonishing incident reported was a fatality caused by the ingestion of a small quantity of finely divided powder insulation which had been spilled. A very useful review of the low temperature thermal conductivity of polymers was presented by Dennis Greig (Leeds) who demonstrated that three distinct temperature
274 Cryogenics 1987 Vol 27 May
regions (T > 25K, 1K < T < 25K, T < 1K) are characteristic of this particular property of polymers. Bob Adams (Bristol) presented some interesting results on the dynamic properties of materials at low temperatures. These were concerned mainly with the damping and dynamic moduli of materials for use in cryoalternators. David Dew-Hughes (Oxford) provided food for thought by generating some question marks over the conventional view that austenitic steels make the best low temperature constructional materials when used in high magnetic fields. They can become highly magnetic for a variety of reasons. The message of this report was that more data is needed. An illuminating and detailed account of the construction of space-bound optical components, which are required to work at liquid helium temperatures for the ISO project, was given by T. Patrick (Mullard Space Science Laboratory). Finally Mike Priddey (Bunting Titanium Ltd) exploded a few myths about titanium. He demonstrated that it isn't as prohibitively expensive and difficult to use as is commonly thought and that its unique properties render it ideal for many cryogenic applications. He had an amusing theory that the reluctance of some people to use titanium may be because they associated its name with the Titanic! This was an excellent meeting with just the right number of participants and well presented papers to allow everybody to get the maximum out of the day. We could do with more like it.
H. Jones Clarendon Laboratory, University of Oxford, UK