Reducing the susceptibility of lumped-element KIDs to two-level system effects. (arXiv:1801.07920v2 [astro-ph.IM] UPDATED)

Reducing the susceptibility of lumped-element KIDs to two-level system effects. (arXiv:1801.07920v2 [astro-ph.IM] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Hornsby_A/0/1/0/all/0/1">A. L. Hornsby</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barry_P/0/1/0/all/0/1">P. S. Barry</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Doyle_S/0/1/0/all/0/1">S. M. Doyle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tang_Q/0/1/0/all/0/1">Q. Y. Tang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shirokoff_E/0/1/0/all/0/1">E. Shirokoff</a>

Arrays of lumped-element kinetic inductance detectors (LEKIDs) optically
coupled through an antenna-coupled transmission line are a promising candidate
for future cosmic microwave background (CMB) experiments. However, the
dielectric materials used for the microstrip architecture are known to degrade
the performance of superconducting resonators. In this paper, we investigate
the feasibility of microstrip coupling to a LEKID, focusing on a systematic
study of the effect of depositing amorphous silicon-nitride on a LEKID. The
discrete and spatially-separated inductive and capacitive regions of the LEKID
allow us to vary the degree of dielectric coverage and determine the
limitations of the microstrip coupling architecture. We show that by careful
removal of dielectric from regions of high electric field in the capacitor,
there is minimal degradation in dielectric loss tangent of a partially covered
lumped-element resonator. We present the effects on the resonant frequency and
noise power spectral density and, using the dark responsivity, provide an
estimate for the resulting detector sensitivity.

Arrays of lumped-element kinetic inductance detectors (LEKIDs) optically
coupled through an antenna-coupled transmission line are a promising candidate
for future cosmic microwave background (CMB) experiments. However, the
dielectric materials used for the microstrip architecture are known to degrade
the performance of superconducting resonators. In this paper, we investigate
the feasibility of microstrip coupling to a LEKID, focusing on a systematic
study of the effect of depositing amorphous silicon-nitride on a LEKID. The
discrete and spatially-separated inductive and capacitive regions of the LEKID
allow us to vary the degree of dielectric coverage and determine the
limitations of the microstrip coupling architecture. We show that by careful
removal of dielectric from regions of high electric field in the capacitor,
there is minimal degradation in dielectric loss tangent of a partially covered
lumped-element resonator. We present the effects on the resonant frequency and
noise power spectral density and, using the dark responsivity, provide an
estimate for the resulting detector sensitivity.

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