We investigate the reproducibility of repeated intercalation of hydrogen in graphene/Ge (110) and the formation of H2 nanobubbles after thermal treatments. By exploiting high-resolution electron energy loss, we obtain direct spectroscopic fingerprints of H2 trapped gas in the samples when nanobubbles are present and we are able to track the effectiveness of H intercalation via the Ge–H vibrational mode. We correlate the effectiveness of interface re-hydrogenation to the presence of structural defects in graphene as highlighted by Raman spectroscopy. The π-plasmon mode of graphene on Ge (110) is investigated as a function of the hydrogen presence at the interface, revealing that, independent of the hydrogen intercalation status, graphene is weakly interacting on Ge (110).

Though their imprint upon the CMB and large-scale structure of the universe remains to this day, Big Bang relic neutrinos (the C nu B) have never been directly observed. This remains an outstanding test of the Standard Model in CDM cosmology and would provide the earliest picture of the universe at only one second after the Big Bang. PTOLEMY aims to make the first direct observation of the C..B by resolving the beta-decay endpoint of atomic tritium. The concept relies upon amassing a target of atomic tritium, developing RF-based trigger and tracking, an EM transverse drift filter, and a cryogenic micro-calorimeter - each of which present novel R&D challenges. A prototype will soon be based at Gran Sasso National Laboratory. Intermediate measurements will be made of the lowest neutrino mass ahead of C..B physics runs set to begin in the 2030s.

The PTOLEMY transverse drift filter is a new concept to enable precision analysis of the energy spectrum of electrons near the tritium β -decay endpoint. This paper details the implementation and optimization methods for successful operation of the filter for electrons with a known pitch angle. We present the first demonstrator that produces the required magnetic field properties with an iron return-flux magnet. Two methods for the setting of filter electrode voltages are detailed. The challenges of low-energy electron transport in cases of low field are discussed, such as the growth of the cyclotron radius with decreasing magnetic field, which puts a ceiling on filter performance relative to fixed filter dimensions. Additionally, low pitch angle trajectories are dominated by motion parallel to the magnetic field lines and introduce non-adiabatic conditions and curvature drift. To minimize these effects and maximize electron acceptance into the filter, we present a three-potential-well design to simultaneously drain the parallel and transverse kinetic energies throughout the length of the filter. These optimizations are shown, in simulation, to achieve low-energy electron transport from a 1 T iron core (or 3 T superconducting) starting field with initial kinetic energy of 18.6 keV drained to < 10 eV (< 1 eV) in about 80 cm. This result for low field operation paves the way for the first demonstrator of the PTOLEMY spectrometer for measurement of electrons near the tritium endpoint to be constructed at the Gran Sasso National Laboratory (LNGS) in Italy.

We discuss the consequences of the quantum uncertainty on the spectrum of the electron emitted by the beta-processes of a tritium atom bound to a graphene sheet. We analyze quantitatively the issue recently raised by Cheipesh, Cheianov, and Boyarsky [Phys. Rev. D 104, 116004 (2021)], and discuss the relevant timescales and the degrees of freedom that can contribute to the intrinsic spread in the electron energy. We perform careful calculations of the potential between tritium and graphene with different coverages and geometries. With this at hand, we propose possible avenues to mitigate the effect of the quantum uncertainty.

We report on an apparatus able to measure the absolute detection efficiency of a detector for electrons in the 30–900 eV range. In particular, we discuss the characterisation of a two-stage chevron microchannel plate (MCP). The measurements have been performed in the LASEC laboratory at Roma Tre University, whit a custom-made electron gun. The very good stability of the beam current in the fA range, together with the picoammeter nominal resolution of 0.01 fA, allowed the measurement of the MCP absolute efficiency ε . We found an ϵ = ( 0.489 ± 0.003 ) with no evident energy dependence. We fully characterised the MCP pulse shape distribution, which is quasi-Gaussian with a well visible peak above the noise level. We measured a 68 % variation of the average pulse height between 30 and 500 eV. Furthermore, with a deeper analysis of the pulse shape, and in particular of the correlation between pulse height, area and width, we found a method to discriminate single- and multi- electron events occurring within a 10 ns time window.

Low Field Optimization of the PTOLEMY Electromagnetic Filter A. Apponi,1, 2 M.G. Betti,3, 4 M. Borghesi,5, 6 A. Boscá,7 F. Calle,7 N. Canci,8 G. Cavoto,3, 4 C. Chang,9, 10 W. Chung,11 A.G. Cocco,12 A.P. Colijn,13, 14 N. D’Ambrosio,8 N. de Groot,15 M. Faverzani,5, 6 A. Ferella,8, 16 E. Ferri,5 L. Ficcadenti,3, 4 P. Garcia-Abia,17 G. Garcia Gomez-Tejedor,18 S. Gariazzo,19 F. Gatti,20 C. Gentile,21 A. Giachero,5, 6 Y. Hochberg,22 Y. Kahn,10, 23 A. Kievsky,24 M. Lisanti,11 G. Mangano,12, 25 L.E. Marcucci,24, 26 C. Mariani,3, 4 J. Martínez,7 M. Messina,8 E. Monticone,19, 27 A. Nucciotti,5, 6 D. Orlandi,8 F. Pandolfi,3 S. Parlati,8 J. Pedrós,7 C. Pérez de los Heros,28 O. Pisanti,12, 25 A.D. Polosa,3, 4 A. Puiu,8, 29 I. Rago,3, 4 Y. Raitses,21 M. Rajteri,19, 27 N. Rossi,8 K. Rozwadowska,8, 29 I. Rucandio,17 A. Ruocco,1, 2 R. Santorelli,17 C.F. Strid,30 A. Tan,11 C.G. Tully,11 M. Viviani,24, 26 U. Zeitler,15 and F. Zhao11 1)INFN Sezione di Roma 3, Roma, Italy 2)Università di Roma Tre, Roma, Italy 3)INFN Sezione di Roma 1, Roma, Italy 4)Sapienza Università di Roma, Roma, Italy 5)INFN Sezione di Milano-Bicocca, Milan, Italy 6)Università di Milano-Bicocca, Milan, Italy 7)Universidad Politécnica de Madrid, Madrid, Spain 8)INFN Laboratori Nazionali del Gran Sasso, L’Aquila, Italy 9)Argonne National Laboratory, Chicago, IL, USA 10)Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL, USA 11)Princeton University, Princeton, NJ, USA 12)INFN Sezione di Napoli, Napoli, Italy 13)Nationaal instituut voor subatomaire fysica (NIKHEF), Amsterdam, The Netherlands 14)University of Amsterdam, Amsterdam, The Netherlands 15)Radboud University, Nijmegen, The Netherlands 16)Università di L’Aquila, L’Aquila, Italy 17)Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Madrid,

We report on the characterization of the response of windowless silicon avalanche photo-diodes to electrons in the 90-900 eV energy range. The electrons were provided by a monoenergetic electron gun present in the LASEC laboratories of University of Roma Tre. We find that the avalanche photo-diode generates a current proportional to the current of electrons hitting its active surface. The gain is found to depend on the electron energy E_e, and varies from 2.147 ± 0.027 (for E_e = 90 eV) to 385.8 ± 3.3 (for E_e = 900 eV), when operating the diode at a bias of V_apd = 350 V. This is the first time silicon avalanche photo-diodes are employed to measure electrons with E_e < 1 keV.

CYGNO experiment is working at the construction of one cubic meter TPC, based on Optical Readout of Gas Electron Multipliers (GEMs), for Directional Dark Matter search. This kind of research demands for very long dataacquisition runs and thus for high operation stability and reliability. This is one of the key elements of INITIUM project (ERC-2018-COG). The performance of such an approach was studied with a 7 liter sensitive volume detector. The detector was kept operative for 10 days in the working conditions able to provide full detection efficiency while continuously monitoring voltages and currents. Even if a few times per day the current drawn by the detector started to increase, these events could be recovered by an automated high voltage cycle. Dead time introduced by these procedures was evaluated to be lesser than 6% and the operation of the detector did not show any deterioration during the 10 days of the test.