Item

Abstract

MADMAX is an experiment for the search of dark matter axions. In order to achieve the required sensitivity for detection, preamplifiers are needed that operate at or close to the quantum limit. Traveling wave parametric amplifiers (TWPA) are a promising tool for accomplishing this in the frequency range around 20 GHz. To reach standard quantum limit, an open challenge is improvement of the added noise in TWPA. One of the main phenomena, which could contribute to the noise, is capacitive dielectric loss. Losses become especially large when going to higher frequencies, as we are looking for when probing the axion mass in the range around 100 μeV, corresponding to a frequency of ∼ 25 GHz, at MADMAX. To further investigate their origin & to reduce them, λ/2-Josephson resonators were built to measure tan(δ) via extraction of quality factors. Two different geometries were compared. For a close metallic ground, separated by a 22nm layer of alumina, internal quality factors are found to be Qi = 216 ± 22 at single-photon level, corresponding to loss tangents of tan(δ) ≈ 5 × 10−3. In the reference geometry without the close ground we find tan(δ) ∼ 104.