arXiv subjects

Cloé Girard-Carillo

Publications and source records attributed to Cloé Girard-Carillo.

5 recordsLinked to original sources

arXiv2026

Single-electron detection in a high-purity Ge device

High-purity germanium (HPGe) detectors are among the most powerful instruments for gamma ray spectroscopy, combining exceptional energy resolution with large active volumes. Although they operate close to the fundamental resolution limit at high energies, their performance at very low energies has long been limited by electronic noise, restricting detection thresholds to above approximately 30 electron-hole pairs ($\sim$100 eV). Here we introduce a cryogenic HPGe detector architecture that achieves single electron-hole pair sensitivity by calorimetrically measuring ionization at temperatures near 20 mK. The device integrates a NbSi transition-edge sensor into a point-contact-inspired geometry, concentrating athermal phonon energy generated during charge drift and enabling eV-scale sensitivity ultimately set by the semiconductor band gap. Beyond single-charge detection, the device rejects the low-energy excess background that limits existing cryogenic low-threshold technologies, establishing a pathway towards discrimination between electron- and nuclear-recoil events below 100 eV. These advances open a route towards next-generation detectors for direct dark matter searches, coherent elastic neutrino-nucleus scattering, and nuclear reactor monitoring for non-proliferation applications.

physics.ins-det↗

arXiv2026

Characterization of Aluminum Microwave SQUID Multiplexers for CE$ν$NS Detection

We present the design, fabrication, and characterization of an aluminum-based six-channel microwave SQUID multiplexer ($μ$MUX) prototype for transition-edge sensor (TES) readout in the RICOCHET experiment. The device consists of aluminum coplanar-waveguide resonators and RF SQUIDs with Dolan-style Al/AlO$_x$/Al Josephson junctions. By measuring the resonator scattering parameters at a range of probe tone frequencies, powers, and flux bias points, we demonstrate agreement between the device response and existing multiplexer models. We also characterize the noise performance in both open-loop and flux-ramping modes. With a high electron mobility transistor (HEMT) amplifier, open-loop measurements yield a flux sensitivity of 1-1.5 $μΦ_0/\sqrt{Hz}$. With flux-ramp modulation, low-frequency 1/f noise is suppressed, and the flux sensitivity is around 3-4 $μΦ_0/\sqrt{Hz}$, corresponding to a current sensitivity of 24-33 $pA/\sqrt{Hz}$ at the input coil. We further demonstrate a reduction in readout noise by incorporating a Josephson traveling-wave parametric amplifier (JTWPA) between the $μ$MUX and the HEMT. This achieves an open-loop flux sensitivity of 0.3-0.6 $μΦ_0/\sqrt{Hz}$ and an effective system noise temperature below 1 K. These results establish aluminum $μ$MUX devices as a viable and extensible readout technology for low-noise cryogenic detector arrays.

physics.ins-det↗

arXiv2025

Combining Hybrid and Opaque Scintillator Techniques in the Search for Double Beta Plus Decays

Double beta plus decay is a rare nuclear disintegration process. Difficulties in its measurement arise from suppressed decay probabilities, experimentally challenging decay signatures and low natural abundances of suitable candidate nuclei. In this article, we propose a new detector concept to overcome these challenges. It is based on the first-time combination of hybrid and opaque scintillation detector technology paired with novel light read-out techniques. This approach is particularly suitable detecting positron (beta plus) signatures. We expect to discover two-neutrino double beta plus decay modes within 1 tonne-week exposure and are able to probe neutrinoless double beta plus decays at several orders of magnitude improved significance compared to current experimental limits.

physics.ins-det↗

arXiv2025

Search for Double Beta Plus Decays with NuDoubt++

The NuDoubt++ experiment proposes a novel detector concept to search for double beta plus decays using a hybrid opaque liquid scintillator. This design combines recent advances in scintillator technologies (namely, slow and opaque media, and optimized wavelength-shifting fibers coupled to silicon photomultipliers) to achieve improved particle identification and background rejection. We present the physics motivations, detector design, first prototype layout, and expected sensitivities for both standard and exotic modes, using 78Kr as an initial target isotope. With this approach, NuDoubt++ aims to make the first observation of positron emitting Standard Model two-neutrino modes and improve current constraints on Beyond Standard Model neutrinoless processes.

hep-ex↗

arXiv2025

LiquidO: Neutrino Detection and Imaging in Opaque Media

For several decades now, scintillator detectors have found a wide range of applications in particle physics, including neutrino detection, the search for dark matter and even medical imaging. These detectors so far have strongly relied on the transparency of the scintillating medium, through which light is typically propagated to surrounding photosensors. In this work, we present the results of a 10 litre prototype based on a novel detection approach where an opaque scintillator medium is used to confine light near its creation point that is then collected by a grid of wavelength-shifting fibres traversing the detector. The prototype is operated with different media, including the novel opaque scintillator NoWaSH whose scattering length varies with temperature. Our results progressively demonstrate the temperature-dependent stochastic confinement of the light, with 90% (80%) of the light being confined within a radius of 5 cm (4 cm) when the scattering length is on the order of a few millimetres. The results also demonstrate the pulse shape resolution of our setup capable of resolving Cherenkov and scintillation light. Altogether, the observations match the performance expected for this new type of detector, whose capabilities are expected to include the imaging of particle interactions down to MeV-energies.

physics.ins-det↗