*James A. Greer¹, Larry Scipioni¹, Alexey Mankevich^2,3, Anton Markelov^2,3, Alexander Molodyk^2,3
1PVD Products, Wilimington, MA; ²SuperOx, Moscow, Russia; ³S-Innovations, Moscow, Russia
The rapidly growing field of compact nuclear fusion technology is driving the need for HTS-equipped electromagnets. The amount of tape needed just to build a single demonstrator reactor outstrips – by an order of magnitude – the present worldwide capacity to produce tape. Thus, higher speed tape manufacturing is a critical need. One of the bottlenecks in the production of buffered tape is the epitaxial MgO layer deposited on amorphous oxide. In the Stanford process, ion beam assisted deposition (IBAD) produces the biaxially textured template for subsequent addition of epitaxial MgO (EPI) by electron beam evaporation on heated substrates. The IBAD growth rate is limited by the available ion beam flux, which must match the arriving flux of MgO molecules at the tape substrate. PVD Products has developed and commercialized a dual-chamber system for high speed production of IBAD/EPI layers. The system can process 1 kilometer of 100 µm thick tape at a speed of 200 meters/hour. Longer lengths of thinner tape are possible due the high capacity electron beam sources. The system features extended length deposition zones with multiple tape passes and, most importantly, a unique IBAD geometry pairing one evaporator with two large rectangular RF ion sources. The EPI layer chamber is likewise equipped with dual evaporation sources to support growth of thick EPI MgO at high processing speed. Multi-pass deposition handles 12 mm wide tape, and the tool is also designed to handle a single lane of 10 cm wide tape, albeit at a lower tape speed of ~50 m/hour. Two dedicated, differentially pumped RHEED chambers provide real-time feedback on film quality of both the IBAD and EPI processes without exposing the RHEED system to evaporant or high gas pressure. The tool has demonstrated processing 1 km of tape in a continuous 5-hour run. Due to the robust design, initial testing has also been extended to web speed up to 350 m/hr while still producing good RHEED patterns from both chambers. We will give an overview of the technology and present results from initial characterization the films deposited on metal tapes, including post-processing of LMO and ReBCO to complete the HTS stack.