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Towards Low-Energy Electron High-Resolution Spectroscopy with Transition-Edge Sensors
Authors:
R. Ammendola,
A. Apponi,
G. Benato,
M. G. Betti,
R. Biondi,
P. Bos,
M. Cadeddu,
A. Casale,
O. Castellano,
G. Cavoto,
L. Cecchini,
E. Celasco,
M. Chirico,
W. Chung,
A. G. Cocco,
A. P. Colijn,
B. Corcione,
N. D'Ambrosio,
M. D'Incecco,
G. De Bellis,
M. De Deo,
N. de Groot,
A. Esposito,
M. Farino,
S. Farinon
, et al. (40 additional authors not shown)
Abstract:
We present a study of the energy resolution of transition-edge sensors (TESs) for the detection of electrons in the 100 eV kinetic energy range. The TES is a Ti-Au bilayer with an active area of $(60 \times 60)$ $μ\text{m}^2$ and a critical temperature of $\sim$ 80 mK. The electron source is based on vertically-aligned multiwall carbon nanotubes located inside the cryostat, with electrons generate…
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We present a study of the energy resolution of transition-edge sensors (TESs) for the detection of electrons in the 100 eV kinetic energy range. The TES is a Ti-Au bilayer with an active area of $(60 \times 60)$ $μ\text{m}^2$ and a critical temperature of $\sim$ 80 mK. The electron source is based on vertically-aligned multiwall carbon nanotubes located inside the cryostat, with electrons generated via field emission. For electrons in the (92 - 99) eV kinetic energy range, we obtain a Gaussian energy resolution for fully-absorbed electrons of (0.479 $\pm$ 0.041 $\pm$ 0.055) eV. When considering the full-width at half-maximum of the peak, the corresponding resolution is of (1.44 $\pm$ 0.17 $\pm$ 0.27) eV. The former represents an improvement of (46 - 60)% with respect to previous results, and is mainly attributed to the reduction in the TES active area. The latter is instead an improvement of over a factor of 20, and is mainly due to the reduction in the emitting area of the electron source, which significantly suppresses electron back-scattering in proximity of the TES. These results represent a major milestone toward high-precision spectroscopy on low-energy electrons, which is a key objective for the PTOLEMY experiment.
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Submitted 25 February, 2026;
originally announced February 2026.
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Ultra-high precision high voltage system for PTOLEMY
Authors:
R. Ammendola,
A. Apponi,
G. Benato,
M. G. Betti,
R. Biondim,
P. Bos,
G. Cavoto,
M. Cadeddu,
A. Casale,
O. Castellano,
E. Celasco,
L. Cecchini,
M. Chirico,
W. Chung,
A. G. Cocco,
A. P. Colijn,
B. Corcione,
N. D'Ambrosio,
M. D'Incecco,
G. De Bellis,
M. De Deo,
N. de Groot,
A. Esposito,
M. Farino,
S. Farinon
, et al. (41 additional authors not shown)
Abstract:
The PTOLEMY project is prototyping a novel electromagnetic filter for high-precision $β$ spectroscopy, with the ultimate and ambitious long-term goal of detecting the cosmic neutrino background through electron capture on tritium bound to graphene. Intermediate small-scale prototypes can achieve competitive sensitivity to the effective neutrino mass, even with reduced energy resolution. To reach a…
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The PTOLEMY project is prototyping a novel electromagnetic filter for high-precision $β$ spectroscopy, with the ultimate and ambitious long-term goal of detecting the cosmic neutrino background through electron capture on tritium bound to graphene. Intermediate small-scale prototypes can achieve competitive sensitivity to the effective neutrino mass, even with reduced energy resolution. To reach an energy resolution better than \SI{500}{meV} at the tritium $β$-spectrum endpoint of \SI{18.6}{keV}, and accounting for all uncertainties in the filtering chain, the electrode voltage must be controlled at the level of a few parts per million and monitored in real time. In this work, we present the first results obtained in this effort, using a chain of commercial ultra-high-precision voltage references, read out by precision multimeters and a \emph{field mill} device. The currently available precision on high voltage is, in the conservative case, as low as \SI{0.2}{ppm} per \SI{1}{kV} single board and $\lesssim$ \SI{50}{mV} over the \SI{10}{kV} series, presently limited by field mill read-out noise. However, assuming uncorrelated Gaussian noise extrapolation, the real precision could in principle be as low as \SI{0.05}{ppm} over \SI{20}{kV}.
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Submitted 22 December, 2025;
originally announced December 2025.
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Phenomenological Modeling of the $^{163}$Ho Calorimetric Electron Capture Spectrum from the HOLMES Experiment
Authors:
F. Ahrens,
B. K. Alpert,
D. T. Becker,
D. A. Bennett,
E. Bogoni,
M. Borghesi,
P. Campana,
R. Carobene,
A. Cattaneo,
A. Cian,
H. A. Corti,
N. Crescini,
M. De Gerone,
W. B. Doriese,
M. Faverzani,
L. Ferrari Barusso,
E. Ferri,
J. Fowler,
G. Gallucci,
S. Gamba,
J. D. Gard,
H. Garrone,
F. Gatti,
A. Giachero,
M. Gobbo
, et al. (24 additional authors not shown)
Abstract:
We present a comprehensive phenomenological analysis of the calorimetric electron capture (EC) decay spectrum of $^{163}$Ho as measured by the HOLMES experiment. Using high-statistics data, we unfold the instrumental energy resolution from the measured spectrum and model it as a sum of Breit-Wigner resonances and shake-off continua, providing a complete set of parameters for each component. Our ap…
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We present a comprehensive phenomenological analysis of the calorimetric electron capture (EC) decay spectrum of $^{163}$Ho as measured by the HOLMES experiment. Using high-statistics data, we unfold the instrumental energy resolution from the measured spectrum and model it as a sum of Breit-Wigner resonances and shake-off continua, providing a complete set of parameters for each component. Our approach enables the identification and tentative interpretation of all observed spectral features, including weak and overlapping structures, in terms of atomic de-excitation processes. We compare our phenomenological model with recent ab initio theoretical calculations, finding good agreement for both the main peaks and the spectral tails, despite the limitations of current theoretical and experimental precision. The model delivers an accurate description of the endpoint region, which is crucial for neutrino mass determination, and allows for a realistic treatment of backgrounds such as pile-up and tails of low-energy components. Furthermore, our decomposition facilitates the generation of Monte Carlo toy spectra for sensitivity studies and provides a framework for investigating systematic uncertainties related to solid-state and detector effects. This work establishes a robust foundation for future calorimetric neutrino mass experiments employing $^{163}$Ho, supporting both data analysis and experimental design.
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Submitted 25 March, 2026; v1 submitted 12 July, 2025;
originally announced July 2025.
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A Demonstration of Slowed Electron ${\bf E} \times {\bf B}$ Drift for PTOLEMY
Authors:
M. Farino,
A. Tan,
A. Apponi,
M. Betti,
M. Borghesi,
A. Casale,
O. Castellano,
G. Cavoto,
L. Cecchini,
E. Celasco,
W. Chung,
A. G. Cocco,
A. Colijn,
B. Corcione,
N. D'Ambrosio,
N. de Groot,
S. el Morabit,
A. Esposito,
M. Faverzani,
A. D. Ferella,
E. Ferri,
L. Ficcadenti,
S. Gamba,
S. Gariazzo,
H. Garrone
, et al. (36 additional authors not shown)
Abstract:
To resolve the effective neutrino mass $m_β$ with an energy resolution of 50~meV, the PTOLEMY experiment has proposed a novel transverse electromagnetic filtering process. Substantially reducing the kinetic energy of tritium $β$-decay electrons by counteracting motion from ${\bf E}$ $\times$ ${\bf B}$ and $\nabla{\rm B}$ drift, the PTOLEMY filter requires an input of emitted electron kinematic inf…
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To resolve the effective neutrino mass $m_β$ with an energy resolution of 50~meV, the PTOLEMY experiment has proposed a novel transverse electromagnetic filtering process. Substantially reducing the kinetic energy of tritium $β$-decay electrons by counteracting motion from ${\bf E}$ $\times$ ${\bf B}$ and $\nabla{\rm B}$ drift, the PTOLEMY filter requires an input of emitted electron kinematic information to generate a tailored, suitable electric field for each candidate. The collaboration proposes to extract these quantities by using antennae to observe the relativistic frequency shift of emitted cyclotron radiation as an electron transits by ${\bf E}$ $\times$ ${\bf B}$ drift through a uniform magnetic field region preceding the filter. Electrons must be contained within this region long enough such that an adequate integrated radiated power signal is received to accurately estimate these kinematics. This necessitates a controlled, slowed drift speed. This paper presents the experimental design to vary ${\bf E}$ $\times$ ${\bf B}$ drift speed of carbon-14 $β$-decay electrons using a custom electrode field cage situated between the pole faces of an electromagnet. Matching our results with high-fidelity simulation, we deduce a capacity to increase particle time of flight by a factor of 5 in the field cage's slow drift region. Limited only by the dimensions of our system, we assert drift speed can be arbitrarily slowed to meet the needs of PTOLEMY's future detector. Actualizing such a system is a crucial milestone in developing the detector, enabling future cyclotron radiation measurements, filter implementation, and source injection.
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Submitted 10 July, 2025; v1 submitted 13 March, 2025;
originally announced March 2025.
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Detection of Low-Energy Electrons with Transition-Edge Sensors
Authors:
Carlo Pepe,
Benedetta Corcione,
Francesco Pandolfi,
Hobey Garrone,
Eugenio Monticone,
Ilaria Rago,
Gianluca Cavoto,
Alice Apponi,
Alessandro Ruocco,
Federico Malnati,
Danilo Serazio,
Mauro Rajteri
Abstract:
We present the first detection of electrons with kinetic energy in the 100 eV range with transition-edge sensors (TESs). This has been achieved with a $(100\times 100)$ $μ$m$^2$ Ti-Au bilayer TES, with a critical temperature of about 84 mK. The electrons are produced directly in the cryostat by an innovative cold source based on field emission from vertically-aligned multiwall carbon nanotubes. We…
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We present the first detection of electrons with kinetic energy in the 100 eV range with transition-edge sensors (TESs). This has been achieved with a $(100\times 100)$ $μ$m$^2$ Ti-Au bilayer TES, with a critical temperature of about 84 mK. The electrons are produced directly in the cryostat by an innovative cold source based on field emission from vertically-aligned multiwall carbon nanotubes. We obtain a Gaussian energy resolution between 0.8 and 1.8 eV for fully-absorbed electrons in the $(90-101)$ eV energy range, which is found to be compatible with the resolution of this same device for photons in the same energy range. This work opens new possibilities for high-precision energy measurements of low-energy electrons.
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Submitted 17 July, 2024; v1 submitted 29 May, 2024;
originally announced May 2024.
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Dark counts in optical superconducting transition-edge sensors for rare-event searches
Authors:
Laura Manenti,
Carlo Pepe,
Isaac Sarnoff,
Tengiz Ibrayev,
Panagiotis Oikonomou,
Artem Knyazev,
Eugenio Monticone,
Hobey Garrone,
Fiona Alder,
Osama Fawwaz,
Alexander J. Millar,
Knut Dundas Morå,
Hamad Shams,
Francesco Arneodo,
Mauro Rajteri
Abstract:
Superconducting transition-edge sensors (TESs) are a type of quantum sensor known for its high single-photon detection efficiency and low background. This makes them ideal for particle physics experiments searching for rare events. In this work, we present a comprehensive characterization of the background in optical TESs, distinguishing three types of events: electrical-noise, high-energy, and ph…
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Superconducting transition-edge sensors (TESs) are a type of quantum sensor known for its high single-photon detection efficiency and low background. This makes them ideal for particle physics experiments searching for rare events. In this work, we present a comprehensive characterization of the background in optical TESs, distinguishing three types of events: electrical-noise, high-energy, and photonlike events. We introduce computational methods to automate the classification of events. For the first time, we experimentally verify and simulate the source of the high-energy events. We also isolate the photonlike events, the expected signal in dielectric haloscopes searching for dark matter dark photons, and achieve a record-low photonlike dark-count rate of $3.6 \times 10^{-4}$ Hz in the 0.8-3.2 eV energy range.
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Submitted 20 September, 2025; v1 submitted 5 February, 2024;
originally announced February 2024.