Melt cast processed BSCCO 2212
Bulk parts of Bi 2212 are manufactured at Nexans Superconductors using the patented Melt Cast Processed (MCP) method. This technique permits the production of a wide variety of shapes e.g. rods, tubes, plates, rings etc. Parts of up to 800 mm in diameter or 400 mm in length can be rapidly cast and annealed to optimise properties.
Bulk rods and tubes are used in current leads. In addition, tubes are employed in inductive fault current limitation and field trapping or further machined in to single and double spirals for magnetic field generation and resistive fault current limitation.
General Material Properties
- Tc (R=0)=90-92K
- Jc (77K, B=0)=600-4000A/cm² (limited by self field in larger parts)
- Jc (4K, B=0)>10 000A/cm²
- heat conductance (77K):<1W/m*K []
- specific heat (77K):~120Ws/Kg*K [] (depending on admixture)
- thermal expansion (77K):3.5*10-6 /K [2]
- contact resistances:~2.0 µohm*cm² at 77K, <0.05 µohm*cm² at 4K
- density: 5.7-6.0g/cm³ (depending on admixture)
4-point bending test: failure point 72 N for rods ø5mm, 257 N for rods ø8mm
Current leads
HTS current leads offer major advantages over conventional all metal current leads. The enabling technology in cryogen free magnet systems they also offer substantial benefits to conventional helium systems where a reduction of the heat load to the 4 K level by more than a factor of 10 offers substantial savings in coolant costs. Additional benefits come from a more compact design of the complete device and an over all reduction in system costs.
Current Leads based on our melt cast processed material have been used successfully in a number of well known projects. We have supplied 6 kA leads for the Eddison Current Controller, for Oxford Instruments cryogen free magnets, for wiggles, SMES systems and for 13 kA and 600 Leads built to the specifications of the LHC at CERN. We are presently developing material to be used in trials for the ITER fusion project.
Thermal conductivity
BSCCO 2212 has the lowest thermal conductivity of all the HTS materials and can be manufactured to carry currents of over 14 kA. This makes it the idea choice for d.c. current leads. It can also be manufactured to make it suitable for a.c. applications
Contacts
Bulk parts can be made with integral low resistance silver contacts as well as fully integrated shunt protection for more stringent conditions.
Custom Solutions
Simple tubes and rods are available for customers who wish to perform custom integration in to their own systems. Alternatively, Nexans SuperConductors collaborates successfully with ACCEL Instruments GmbH to offer full leads systems for both low and high current applications. Please contact us to discuss your exact system requirements and we can propose a lead design suitable for easy attachment to your system.
Selecting a lead for your system.
Tubes and rods with integral silver contacts are manufactured in a variety of lengths and diameters. Because critical current is a function of both magnetic field and temperature it is important to select a rod which will operate safely under the most stringent conditions which is may face in you applications. The behavior of our rods has been well characterized from 4K to 77K and in fields up to 6T. You can use the information here to select the rod which in most suitable for you or simply call and tell us your system conditions and we will be glad to advise you on selection and calculate the corresponding heat leak for you.
|
