The development of reactor technologies and neutrino physics by means of nuclear reactors requires unceasingly refining and extending knowledge of reactors as an antineutrino source. By employing new ...data on the reactor-antineutrino spectrum and updated nuclear databases and upon taking into account special features of fuel burnup, the thermal energy released in the reactor core per fission event is calculated for a standard operating period of a thermal-neutron reactor.
The operation of floating nuclear power units in nonnuclear-weapon states does not involve the management of fresh and used nuclear fuel, and the nuclear reactor of the power unit must be ...hermetically sealed in the manufacturing state. In relation to this, a challenging aspect of the application of the IAEA safeguards is the independent verification and confirmation of the state’s information regarding the declared operating modes of the nuclear power unit and the quality and quantity of nuclear fuel used to this end. The currently available technologies for detecting reactor antineutrinos are shown to be capable of providing the IAEA with independent control of a floating power unit reactor; a standalone mobile or stationary neutrino detector may be used to confirm the declared operating modes of the reactor and indirectly confirm the quantity and quality of nuclear material contained in the reactor.
A technique is developed for reconstructing reactor antineutrino spectra from fission products of uranium and plutonium isotopes. Cumulative antineutrino spectra of
,
, and
thermal-neutron fission ...products and
fast-neutron fission products are calculated using the presented reconstruction algorithm and the cumulative beta spectra measured at the Institut Laue–Langevin, Technical University of Munich, and National Research Center “Kurchatov Institute.” Approximations used in the model are described, errors of the results are analyzed, and a comparison of the spectra obtained to the calculations in other works is made.
The evolution of the reactor-antineutrino spectrum and the evolution of the spectrum of positrons from the inverse-beta-decay reaction in the course of reactor operation and after reactor shutdown ...are considered. The present-day status in determining the initial reactor-antineutrino spectrum on the basis of spectra of beta particles from mixtures of products originating from uranium and plutonium fission is described. A local rise of the experimental spectrum of reactor antineutrinos with respect to the expected spectrum is studied.
We present the results of a search for dark matter weakly interacting massive particles (WIMPs) in the mass range below 20 GeV/c^{2} using a target of low-radioactivity argon with a 6786.0 kg d ...exposure. The data were obtained using the DarkSide-50 apparatus at Laboratori Nazionali del Gran Sasso. The analysis is based on the ionization signal, for which the DarkSide-50 time projection chamber is fully efficient at 0.1 keVee. The observed rate in the detector at 0.5 keVee is about 1.5 event/keVee/kg/d and is almost entirely accounted for by known background sources. We obtain a 90% C.L. exclusion limit above 1.8 GeV/c^{2} for the spin-independent cross section of dark matter WIMPs on nucleons, extending the exclusion region for dark matter below previous limits in the range 1.8-6 GeV/c^{2}.
The DarkSide-50 direct-detection dark matter experiment is a dual-phase argon time projection chamber operating at Laboratori Nazionali del Gran Sasso. This paper reports on the blind analysis of a ...(16 660±270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We find no events in the dark matter selection box and set a 90% C.L. upper limit on the dark matter–nucleon spin-independent cross section of 1.14×10−44 cm2 (3.78×10−44 cm2, 3.43×10−43 cm2) for a WIMP mass of 100 GeV/c2 (1 TeV/c2, 10 TeV/c2).
We report on the search for dark matter WIMPs in the mass range below 10 GeV/c$^2$, from the analysis of the entire dataset acquired with a low-radioactivity argon target by the DarkSide-50 ...experiment at LNGS. The new analysis benefits from more accurate calibration of the detector response, improved background model, and better determination of systematic uncertainties, allowing us to accurately model the background rate and spectra down to 0.06 keV$_{er}$. A 90% C.L. exclusion limit for the spin-independent cross section of 3 GeV/c$^2$ mass WIMP on nucleons is set at 6$\times$10$^{-43}$ cm$^2$, about a factor 10 better than the previous DarkSide-50 limit. This analysis extends the exclusion region for spin-independent dark matter interactions below the current experimental constraints in the $1.2, 3.6$ GeV/c$^2$ WIMP mass range.
Abstract
The stability of a dark matter detector on the timescale of a few years is a key
requirement due to the large exposure needed to achieve a competitive sensitivity. It is
especially crucial ...to enable the detector to potentially detect any annual event rate modulation,
an expected dark matter signature. In this work, we present the performance history of the
DarkSide-50 dual-phase argon time projection chamber over its almost three-year
low-radioactivity argon run. In particular, we focus on the electroluminescence signal that
enables sensitivity to sub-keV energy depositions. The stability of the electroluminescence yield
is found to be better than 0.5%. Finally, we show the temporal evolution of the observed event
rate around the sub-keV region being consistent to the background prediction.
Finding unequivocal evidence of dark matter interactions in a particle detector is a major goal of research in physics. Liquid argon time projection chambers offer a path to probe Weakly Interacting ...Massive Particles scattering cross sections on nuclei down to the so-called neutrino floor, in a mass range from a few GeV to hundreds of TeV. Based on the successful operation of the DarkSide-50 detector at LNGS, a new and more sensitive experiment, DarkSide-20k, has been designed and is now under construction. A thorough understanding of the DarkSide-50 detector response and, therefore, of all types of events observed in the detector, is essential for the optimal design of the new experiment. In this article, we report on a specific set of events, namely, standard two-pulse scintillation–ionization signals with a third small amplitude pulse, occurring within the 440μs data acquisition window of standard events. Some of these events are due to the photoionization of the TPC cathode. We compare our results with those published by collaborations using liquid xenon time projection chambers, which observed a similar phenomenon, and, in particular, with a recent paper by the LUX Collaboration (D.S. Akerib et al. Phys.Rev.D 102, 092004 (2020)) From the measured rate of these events, we estimate for the first time the quantum efficiency of the tetraphenyl butadiene deposited on the DarkSide-50 cathode at wavelengths of around 128 nm, in liquid argon. Also, both experiments observe events likely related to the photoionization of impurities in the liquid. The probability of photoelectron emission per unit length turns out to be an order of magnitude lower in DarkSide-50 than in LUX.
A Geant4-based Monte Carlo package named G4DS has been developed to simulate the response of DarkSide-50, an experiment operating since 2013 at LNGS, designed to detect WIMP interactions in liquid ...argon. In the process of WIMP searches, DarkSide-50 has achieved two fundamental milestones: the rejection of electron recoil background with a power of ∼107, using the pulse shape discrimination technique, and the measurement of the residual 39Ar contamination in underground argon, ∼3 orders of magnitude lower with respect to atmospheric argon. These results rely on the accurate simulation of the detector response to the liquid argon scintillation, its ionization, and electron-ion recombination processes. This work provides a complete overview of the DarkSide Monte Carlo and of its performance, with a particular focus on PARIS, the custom-made liquid argon response model.
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