PLD TAPE MANUFACTURE FUSION’S FAST TRACK: EXCIMER LASERS


SUPERCHARGE HTS-TAPE PRODUCTION RALPH DELMDAHL, COHERENT LASERSYSTEMS GMBH & CO. KG


Pulsed Laser Deposition grows the delicate REBCO layer by the metre


Nuclear fusion as a clean, virtually limitless power source is on the road to commercialisation. At the heart of this ongoing energy revolution lies REBCO (Rare Earth Barium Copper Oxide) tape, a high-temperature superconductor (HTS) that can carry immense electrical currents with zero resistance at unprecedented mgnetic field strength of 20 tesla and beyond. But producing REBCO thin films on tape substrates at scale and with the crystalline properties needed for magnetic fusion reactors has long been a bottleneck. Enter Pulsed Laser Deposition (PLD), a technique that is quietly transforming the landscape of HTS manufacturing driven by ever increasing excimer laser power levels.


FUSION-PROOF HTS-TAPES WITH PLD


HTS-tapes have a multi-layer structure. Typically, a Hastelloy substrate providing mechanical stability is coated with buffer films followed by the current underpinning the REBCO layer which is then protected by thin Ag and Cu


20 | LASER USER 118 DECEMBER 2025


coatings (Figure 1). The rate and performance determining process is the growth of the REBCO layer usually applied in the chemical composition YBa2


HTS-tape is about 60 µm thick and 12 mm wide (Figure 2) and is produced in batch lengths of many 100 m.


Cu3 O7


As a coating method for multi- element oxides, PLD offers unique advantages in controlling REBCO film quality, grain boundaries, and


. The final


nanostructural defects that act as flux pinning centers. The latter are essential for achieving high critical current even at the very high- magnetic fields present in a fusion reactor. Albeit PLD-made tapes need to be scaled to bring fusion energy to life.


SURGING TAPE DEMAND DRIVEN BY FUSION


Unlike conventional superconductors, REBCO


Figure 1: Sketch of a typical HTS-tape layer sequence


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