High Yield and High Throughput Reactive IBAD MgO Process for Long-length, HTS Wire Production at SuperPower
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1150-RR05-04
High Yield and High Throughput Reactive IBAD MgO Process for Long-length, HTS Wire Production at SuperPower Xuming Xiong, Karol Zdun, Sungjin Kim, Andrei Rar, Senthil Sambandam, Robert Schmidt, Yimin Chen, Kenneth Lenseth and Venkat Selvamanickam SuperPower, Inc., 450 Duane Ave, Schenectady, NY 12304 USA ABSTRACT SuperPower’s IBAD (ion beam assisted deposition) MgO process has been changed to reactive ion beam sputtering of Mg metal target instead of MgO ceramic target, which gives ~ 60 % increase in deposition rate. The process speed was increased from 195 m/h* to 360 m/h. Texture of IBAD MgO tapes by this reactive process was found to degrade faster during a long length run. This uniformity issue was resolved with feedback control during long runs and from run to run. The bottleneck of the alumina layer process due to slow ion beam sputtering deposition was removed by new high rate reactive magnetron sputtering at transition mode. The new alumina process speed can be as high as 3,000 m/h in our Pilot Buffer system. The yttria layer process was also changed to high rate reactive magnetron sputtering at transition mode with achievable speed as high as 10,000 m/h in our Pilot Buffer system. The routine production speed of alumina and yttria is 750 m/h due to a limitation of the tape driving system. The high rate magnetron-sputtered alumina/yttria yields the same texture of IBAD MgO as ion beam sputtered alumina/yttria. Now we are routinely producing IBAD MgO template tapes of ~ 1.4 km with a uniform in-plane texture ~ 6-7 degrees. A record high critical current of 813 A/cm over a one meter length and a world record critical current times length value of > 233,810A-m was obtained with our routinely-produced high throughput IBAD MgO buffers. The requirements for a better IBAD texturing layer than IBAD MgO are also suggested. 1. INTRODUCTION SuperPower Inc is developing and manufacturing HTS (high temperature superconductor) coated conductors for commercial use. Challenges for HTS coated conductors to become commercially viable are long length, high quality, and low cost. High throughput processing is a must for cost reduction and production capacity to meet market needs. SuperPower uses an IBAD MgO approach [1-4] to make HTS coated conductor tape. An IBAD MgO or IBAD MgO-like process is the most promising high throughput, high quality process to meet the market requirements. The in-plane texture of our routinely-manufactured HTS wire is between 2-3 degrees. Such an excellent texture opens the way for extremely high Ic (critical current) which is a very effective way to reduce cost and increase wire performance. Another advantage of the IBAD MgO process is the flexibility to choose different substrates to meet different requirements of cost, processes and applications. For example, by choosing a thin and flexible substrate, this type of HTS wire can greatly enhance the engineering current density for high-field coil applications. The separation of the barrier layer and the texturing layer in the IBAD MgO-l
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