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Figure 3
Real part of impedance versus frequency for three different structures in double logarithmic representation. Structure I (top) is matched to 100 GHz. The inner radius r1 is 2 mm, the permittivity of the dielectric layer [\varepsilon^{\,\prime}] is 3.8 (fused silica), [\varepsilon^{\,\prime\prime}] is assumed to be 4×10-4 and the layer thickness d1 is 225 µm. Structure II (middle) has the following parameters: radius r1 = 1 mm, [\varepsilon^{\,\prime}] = 1.1, [\varepsilon^{\,\prime\prime}] = 4×10-4 and d1 = 1 µm. It reaches a resonance frequency of 6.6 THz. For structure III (bottom) it is finally assumed that the layer thickness d1 is reduced to 0.1 µm, while all other parameters are identical to the second structure. The resonance frequency of the third structure is 15 THz. The outer layer is in all cases copper with a thickness larger than the skin depth and a conductivity of [{\sigma_{0}}] of 58.8 (MΩ m)−1. For comparison the impedance of a pure resistive copper tube without surface roughness is included in the bottom plot.

Journal logoJOURNAL OF
SYNCHROTRON
RADIATION
ISSN: 1600-5775
Volume 28| Part 1| January 2021| Pages 18-27
https://doi.org/10.1107/S1600577520014058
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