High sensitivity phonon-mediated kinetic inductance detector with combined amplitude and phase read-out

TL;DR

This paper presents an improved aluminum Kinetic Inductance Detector (KID) with enhanced geometry and combined amplitude-phase read-out, achieving nearly halved energy resolution for cryogenic light detection in rare event searches.

Contribution

The paper introduces a novel KID design and combined read-out method that significantly improves energy resolution over previous prototypes.

Findings

Achieved baseline resolution of 82±4 eV with a single KID.

Demonstrated the effectiveness of combined amplitude and phase analysis.

Improved KID geometry and quality factor contributed to performance enhancement.

Abstract

The development of wide-area cryogenic light detectors with good energy resolution is one of the priorities of next generation bolometric experiments searching for rare interactions, as the simultaneous read-out of the light and heat signals enables background suppression through particle identification. Among the proposed technological approaches for the phonon sensor, the naturally-multiplexed Kinetic Inductance Detectors (KIDs) stand out for their excellent intrinsic energy resolution and reproducibility. To satisfy the large surface requirement (several cm$^2$) KIDs are deposited on an insulating substrate that converts the impinging photons into phonons. A fraction of phonons is absorbed by the KID, producing a signal proportional to the energy of the original photons. The potential of this technique was proved by the CALDER project, that reached a baseline resolution of 154$\pm$7 eV RMS by sampling a 2$\times$2 cm$^2$ Silicon substrate with 4 Aluminum KIDs. In this paper we present a prototype of Aluminum KID with improved geometry and quality factor. The design improvement, as well as the combined analysis of amplitude and phase signals, allowed to reach a baseline resolution of 82$\pm$4 eV by sampling the same substrate with a single Aluminum KID.