Superconducting magnesium diboride films for levitation of laser targets

THIN SOLID FILMS

卷:710

Article

Aji, L. B. Bayu¹  Baker, A. A.¹  Bae, J. H.²  Beckham, J. L.¹  Jacob, R. E.¹  Shin, S. J.¹  McCall, S. K.¹  Kucheyev, S. O.¹ 

[1] Lawrence Livermore Natl Lab, Livermore, CA 94550 USA

[2] Gen Atom, San Diego, CA 92186 USA

关键词: Magnesium diboride;    Superconductivity;    Planar substrates;    Spherical substrates;    Vapor annealing;    Solid-phase reactive inter-diffusion;   

DOI  :  10.1016/j.tsf.2020.138260

来源: Elsevier

【 摘 要 】

Inertial confinement fusion targets would benefit from being levitated inside hohlraums to avoid capsule sup-port-related implosion perturbations. Levitation inside a magnetic trap requires coating the capsule with a thin film that is superconducting at 20 K. Such non-epitaxial film growth on non-planar substrates is challenging. Here, we study Mg vapor annealing and solid-phase reactive inter-diffusion methods to form superconducting magnesium diboride (MgB2) films on different planar and spherical carbon substrates, evaluating glassy carbon, polycrystalline diamond made by chemical vapor deposition, and carbon deposited by magnetron sputtering of graphite targets. Thin films of B and Mg are produced by magnetron sputtering onto stationary planar or rolling spherical substrates and annealed at either 600 or 850 circle C in Mg vapor. The films are characterized by a com-bination of high-energy ion scattering, electron microscopy, and magnetometry. Results show that the critical superconducting temperature of resultant films depends on film microstructure and oxygen impurity content. The formation of MgB2 films is also strongly substrate dependent, even in this case of non-epitaxial growth. Important factors to consider are oxygen outgassing of the substrate during thermal processing, substrate surface roughness, and the matching of thermal expansion coefficients of different layers in the multilayer structure.

【 授权许可】

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