Shaping magnetic fields with superconductor-metamaterial hybrids

• Autores: Jordi Prat Camps
• Directores de la Tesis: Carles Navau Ros (dir. tes.), Alvaro Sanchez Moreno (dir. tes.)
• Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2015
• Idioma: inglés
• Tribunal Calificador de la Tesis: Xavier Obradors Berenguer (presid.), Luis Martín Moreno (secret.), Martin Wegener (voc.)
• Materias:
  • Física
    • Electromagnetismo
      • Magnetismo
• Enlaces
  • Tesis en acceso abierto en:  TDX  DDD 
• Resumen

  • Magnetism is very important in various areas of science and technology, covering a wide range of scales and topics. In this thesis we present the theoretical development and the experimental realization of various novel devices to control magnetic fields. Their design is based on different strategies; transformation optics theory is combined with solutions directly obtained from Maxwell equations, and ideal designs are turned into real devices combining superconducting and ferromagnetic materials forming different magnetic metamaterials.

    We first study the cloaking of magnetic fields. Analogous to the concept of an "invisibility" cloak for light, a cloak for static magnetic fields prevents fields to penetrate in its interior and makes the cloak itself and its content magnetically undetectable from the exterior. Different designs of magnetic cloak are developed and a bilayer superconductor-ferromagnetic cylindrical cloak is experimentally built and tested.

    The concentration of magnetic fields is also addressed. A cylindrical magnetic concentrating shell is designed, demonstrating that it concentrates external fields in its interior hole and it also expels the field of internal sources towards the exterior. Different concentrating shells are experimentally built using superconducting and ferromagnetic materials and their properties are validated. We also demonstrate that concentrating shells increase the magnetic coupling between circuits. We apply this property to experimentally demonstrate they enhance the wireless transfer of power.

    The transfer of static magnetic fields is also studied. Different from electromagnetic waves that easily propagate in waveguides or optical fibers, magnetic fields rapidly decay as one moves far from the source. To overcome this limitation we develop the magnetic hose, a design that allows to transfer static magnetic fields to arbitrary distances and can be realized with an adequate combination of superconducting and ferromagnetic shells. The design is validated using numerical calculations and analytical developments. Some hoses are experimentally built and their properties are demonstrated.

    Finally we develop a magnetic wormhole. Inspired by cosmological wormholes, that connect two points in space through a path that is out of the conventional 3D space, we study an analogous effect for static magnetic fields. The magnetic wormhole magnetically connects two points in space through a path that is magnetically undetectable. It is composed of an interior magnetic hose surrounded by a spherical superconducting shell and a spherical ferromagnetic metasurface. An actual magnetic wormhole is experimentally built and its properties are demonstrated.

    To sum up, this thesis contains the theoretical development and the experimental realization of different devices to manipulate magnetic fields. In addition to addressing different particular problems, like magnetic cloaking, concentration or magnetic field transfer, this research has resulted in a whole set of new "tools" to shape and control static magnetic fields in a general way.