Speaker
Description
The HOLMES experiment investigates the electron neutrino mass by studying the end point of the electron-capture decay spectrum of $^{163}$Ho. The detector technology is based on transition edge sensors (TESs) microcalorimeters.
During the first phase of the experiment, the simultaneous readout of multiple detectors was performed via microwave SQUID multiplexing ($\mu$MUX). However, the high cost per detector of this multiplexing technology limits neutrino mass measurements below $0.1\,\mathrm{eV}$.
In the next phase, HOLMES+, the multiplexed readout will instead be performed with kinetic inductance current sensors (KICSs).
A KICS consists of a lumped element tunable resonator whose inductance is mainly governed by the kinetic inductance of the superconducting material. Thus, its resonance frequency can be modulated upon a current signal, thanks to the current-sensitivity of the kinetic inductance.
This novel multiplexing technology brings several advantages if compared to the $\mu$MUX approach, including ease of microfabrication, with a single lithographic layer, high yield and low costs, as well as a potentially higher multiplexing factor and temporal resolution. This will increase the number of points on the signal rising slope, allowing the distinction of signals pile-up.
In this contribution, we report our recent results in the development of KICS based on thin NbTiN films. We discuss the design and simulation of the first prototypes, with several KICSs coupled to a common transmission line, and we show their successful operation at cryogenic temperatures. We demonstrate the insertion of a persistent current in the circuit to fix an optimal working point, as well as the expected frequency response of the devices upon a current signal, achieving the detection of a test gaussian-shaped pulse.
| Collaboration or Other Affiliation | Holmes |
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