Attenuation in Superconducting Rectangular Waveguides

作者：Yeap Kim Ho^*; Teh Joyce Shu Mei; Nisar Humaira; Yeong Kee Choon; Hirasawa Kazuhiro

来源：Frequenz, 2015, 69(3-4): 111-117.

DOI：10.1515/freq-2014-0078

• superconducting waveguide
• complex conductivity
• attenuation
• propagation constant
• cutoff frequency
• gap frequency

We present an accurate analysis on the attenuation of waves, propagating in rectangular waveguides with superconducting walls. The wavenumbers k(x) and k(y) in the x and y directions, respectively, are first obtained as roots of a set of transcendental equations developed by matching the tangential fields at the surface of the wall with the electrical properties of the wall material. The complex conductivity of the superconducting waveguide is obtained from the extended Mattis-Bardeen theory. The propagation constant k(z) is found by substituting the values of k(x) and ky into the dispersion relation. We have computed and compared the loss in the waveguides below and above the critical temperature. At frequencies above the cutoff frequency f(c) but below the gap frequency f(g), the loss in the superconducting waveguide is significantly lower than that in a normal conducting waveguide. Above the gap frequency, however, the result indicates that the attenuation in the waveguide below the critical temperature is higher than that at room temperature. We attribute the higher loss as due to the higher surface resistance and field penetration for superconducting waveguides operating above the gap frequency.

• 出版日期2015-3