First step towards application of high‐temperature superconductors for planar magnetic lenses

The feasibility of high‐temperature superconductors for applications in particle optics is discussed. Although high Tc superconducting coils and wire are not available yet, we conclude that thin films are very promising for ironless magnetic lenses due to their high maximum current density and because they can be very accurately patterned. However, a stack of 10–100 layers will be needed to fulfil the field strength and rotational symmetry requirements. Initial experimental results obtained with a superconducting YBa2Cu3O7-x film patterned with a 50‐turn spiral‐shaped coil are presented. The maximum critical current density obtained in the 50‐turn spiral was 10⁴ A/cm² at 30 K. The best way to stack the films would be a multilayer fabrication process, but this is not yet available. As an intermediate step, we developed a pattern suitable for face‐to‐face stacking and we propose an alignment technique based on capacitive position sensors.