1. Supercool Group Members: Naomi Kohen Chris Kinney Andy Lin David Schoen Spring 2004 Mission: Utilize unique properties of high temperature superconducting tape to make a superior actuator. Magnetic field (Tesla, cm) 1 amp, room temperature Acknowledgements: Professor Yet-Ming Chiang, Professor John B Vander Sande, Yin-Lin Xie, David Bono, Ken Stone, Ed Moriarty, Leslie Bromberg, 3.082 staff We received BSSCO 2223 high temperature superconducting tape from American Superconductor. BSSCO 2223 is a type 2 ceramic superconducting material. The exact mechanism of superconductivity in these materials is poorly understood. Superconductivity in type 1 superconductors is due to the coordinated movement of electrons linked by lattice phonon interactions. The mechanism in type 2 superconductors is believed to be similar, but involve positive “holes.” BSSCO 2223 lattice structure Tape structure At least in principle superconducting wire could be extremely useful in building an actuator. It can safely carry much more current than traditional conductors. The tape has other limitations though. The amount of current it can carry and stay superconducting, the critical current, depends on the magnetic field parallel and perpendicular to the current direction. In our tape, the current also depends on the diameter through which the tape is bent. We decided to make a solenoid actuator, which could be used for an electrical clamp or punch. Such a device consists of a coil which carries current, producing a magnetic field which acts on an element inside the coil. In our case this was an iron slug. In order to determine the appropriate dimensions for the coil, we experimentally determined the minimum diameter through which we could bend our wire, then did theoretical calculations to determine what length coil would produce the maximum force. We estimated that our coil would be able to run at 30 amps, and produce a 80 N force. Magnetic field in a solenoid Critical current measurement for 5 cm diameter loop After these considerations, we decided to make the coil 5 cm in diameter and 5 cm high. We constructed an apparatus to hold the coil in a liquid nitrogen bath that would also allow the iron core to move freely and wound our coil insulating each layer with Kapton © tape. Initial Apparatus Design Milling Apparatus Once the solenoid was fabricated we attempted to characterize its performance in a number of tests. Critical current of the final solenoid was 55 amps. The maximum magnetic field was 1.8 kOersted The maximum force was 60N. Force vs. displacement for a similar sized commercial copper solenoid Our solenoid fails to perform as well as a similar sized copper solenoid running at room temperature. The severe self field limitations prevented us from taking advantage of the superconducting properties of the tape at liquid N2 temperatures. Until superconducting wire with better self field properties is realized, conventional conductors will be better for this particular application. The performance of the device will improve drastically at sub-liquid nitrogen temperatures and this could be explored. YBCO high temperature superconducting tape is almost ready for commercial production, and this tape could perhaps be successfully utilized for this application. We did not investigate the possibility of using the superconductor to fabricate a persistent actuator due to the difficulty of constructing electrically superconducting junctions. This could be explored though. References: American superconductor website (www.amsuper.com) Montgomery, D. Bruce. Solenoid Magnet Design: The Magnetic and Mechanical Aspects of Resistive and Superconducting Systems. Wiley-Interscience, New York. 1969. Our final assembled solenoid.