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

Abstract

Developing wide-area cryogenic light detectors with baseline resolution better than 20 eV 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. The potential of this technique was proved by the CALDER project, that reached a baseline resolution of 154 ± 7 eV RMS by sampling a 2×2 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 ± 4 eV by sampling the same substrate with a single Aluminum KID.

Measurements and Simulations of Athermal Phonon Transmission from Silicon Absorbers to Aluminum Sensors

“…Once the resonance is calibrated we choose the most sensitive frequency (or frequencies, in the case of reading several KIDs through the same line) and excite the resonators at an adequate power level [39]. We run an amplitude threshold trigger algorithm on the continuously acquired signals to capture particle passages through the detector, and register a window of configurable length around the position of each trigger.…”

“…The contact area between Si and Teflon is lower than 3 mm 2 at every support. For detailed results of this prototype, see [39]. The second prototype, that we label as P4, is a 375 µm thick Si chip with a size of 2×2 cm 2 and containing 4 KIDs (see Fig.…”

“…High powers feature in general a better SNR, as the noise in our setup is dominated by the amplifier and goes with 1/ P µν , but as we raise P µν the resonances show an increasing distortion and the relationship of Eq. 4 is not longer valid [39]. Therefore we perform a power scan and select the largest P µν before distortion.…”

CALDER: Cryogenic light detectors for background-free searches

“…Since the phase signal showed an excess of noise at low frequency that was not present in the amplitude signal, a sensible improvement in the energy resolution was obtained by combining the two signals. With this detector an energy resolution of 80 eV RMS and a phonon collection efficiency of about 10% were obtained [25]. The origin of the low frequency phase noise is still under investigation.…”

Potentialities of the future technical improvements in the search of rare nuclear decays by bolometers

“…In the last 3 year the CALDER 99 project developed and tested several KID detectors using Aluminum as superconducting material. [102][103][104][105][106][107][108][109] With a 4 mm 2 single KID resonator on a 2x2 cm 2 substrate, an energy resolution of about 80 eV has been achieved. 108 The energy resolution of KIDs scales as T c / √ QL.…”