Neutron-induced background in the CONUS experiment

CONUS is a novel experiment aiming at detecting elastic neutrino nucleus scattering in the fully coherent regime using high-purity Germanium (Ge) detectors and a reactor as antineutrino ($\bar\nu$) source. The detector setup is installed at the commercial nuclear power plant in Brokdorf, Germany, at a very small distance to the reactor core in order to guarantee a high flux of more than 10$^{13}\bar\nu$/(s$\cdot$cm$^2$). For the experiment, a good understanding of neutron-induced background events is required, as the neutron recoil signals can mimic the predicted neutrino interactions. Especially neutron-induced events correlated with the thermal power generation are troublesome for CONUS. On-site measurements revealed the presence of a thermal power correlated, highly thermalized neutron field with a fluence rate of (745$\pm$30)cm$^{-2}$d$^{-1}$. These neutrons that are produced by nuclear fission inside the reactor core, are reduced by a factor of $\sim$10$^{20}$ on their way to the CONUS shield. With a high-purity Ge detector without shield the $\gamma$-ray background was examined including highly thermal power correlated $^{16}$N decay products as well as $\gamma$-lines from neutron capture. Using the measured neutron spectrum as input, it was shown, with the help of Monte Carlo simulations, that the thermal power correlated field is successfully mitigated by the installed CONUS shield. The reactor-induced background contribution in the region of interest is exceeded by the expected signal by at least one order of magnitude assuming a realistic ionization quenching factor of 0.2.Comment: 28 pages, 28 figure

Constraints on elastic neutrino nucleus scattering in the fully coherent regime from the CONUS experiment

We report the best limit on coherent elastic scattering of electron antineutrinos emitted from a nuclear reactor off germanium nuclei. The measurement was performed with the CONUS detectors positioned at 17.1m from the 3.9GWth reactor core of the nuclear power plant in Brokdorf, Germany. The antineutrino energies of less than 10 MeV assure interactions in the fully coherent regime. The analyzed dataset includes 248.7 kgd with the reactor turned on and background data of 58.8 kgd with the reactor off. With a quenching parameter of k = 0.18 for germanium, we determined an upper limit on the number of neutrino events of 85 in the region of interest at 90% confidence level. This new CONUS dataset disfavors quenching parameters above k = 0.27, under the assumption of standard-model-like coherent scattering of the reactor antineutrinos

First upper limits on neutrino electromagnetic properties from the CONUS experiment

We report first constraints on neutrino electromagnetic properties from neutrino-electron scattering using data obtained from the CONUS germanium detectors, i.e. an upper limit on the effective neutrino magnetic moment and an upper limit on the effective neutrino millicharge. The electron antineutrinos are emitted from the 3.9 GW$_\mathrm{th}$ reactor core of the Brokdorf nuclear power plant in Germany. The CONUS low background detectors are positioned at 17.1 m distance from the reactor core center. The analyzed data set includes 689.1 kg$\cdot$d collected during reactor ON periods and 131.0 kg$\cdot$d collected during reactor OFF periods in the energy range of 2 to 8 keV. With the current statistics, we are able to determine an upper limit on the effective neutrino magnetic moment $\mu_\nu < 7.5\cdot10^{-11}\,\mu_B$ at 90% confidence level. From this first magnetic moment limit we can derive an upper bound on the neutrino millicharge of $\vert$q$_{\nu}\vert < 3.3\cdot10^{-12}\,e_0$

Full background decomposition of the CONUS experiment

The CONUS experiment is searching for coherent elastic neutrino nucleus scattering of reactor anti-neutrinos with four low energy threshold point-contact high-purity germanium spectrometers. An excellent background suppression within the region of interest below 1keV (ionization energy) is absolutely necessary to enable a signal detection. The collected data also make it possible to set limits on various models regarding beyond the standard model physics. These analyses benefit as well from the low background level of ~10d$^{-1}$kg$^{-1}$below 1keV and at higher energies. The low background level is achieved by employing a compact shell-like shield, that was adapted to the most relevant background sources at the shallow depth location of the experiment: environmental gamma-radiation and muon-induced secondaries. Overall, the compact CONUS shield including the active anti-coincidence muon-veto reduces the background by more than four orders of magnitude. The remaining background is described with validated Monte Carlo simulations which include the detector response. It is the first time that a full background decomposition in germanium operated at reactor-site has been achieved. Next to remaining muon-induced background, $^{210}$Pb within the shield and cryostat end caps, cosmogenic activation and air-borne radon are the most relevant background sources. The reactor-correlated background is negligible within the shield. The validated background model together with the parameterization of the noise are used as input to the likelihood analyses of the various physics cases

Large-size sub-keV sensitive germanium detectors for the CONUS experiment

Intense fluxes of reactor antineutrinos offer a unique possibility to probe the fully coherent character of elastic neutrino scattering off atomic nuclei. In this regard, detectors face the challenge to register tiny recoil energies of a few keV at the maximum. The CONUS experiment was installed in 17.1 m distance from the reactor core of the nuclear power plant in Brokdorf, Germany, and was designed to detect this neutrino interaction channel by using four 1 kg-sized point contact germanium detectors with sub-keV energy thresholds. This report describes the unique specifications addressed to the design, the research and development, and the final production of these detectors. It demonstrates their excellent electronic performance obtained during commissioning under laboratory conditions as well as during the first two years of operation at the reactor site which started on April 1, 2018. It highlights the long-term stability of different detector parameters and the achieved background levels of the germanium detectors inside the CONUS shield setup.Comment: (18 pages, 12 figures

Química na Hora do Recreio

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Áudios para aulas de Química: uma análise do Portal Dia a Dia Educação

A utilização de áudios em sala de aula não tem sido muito utilizada nos últimos anos, entretanto existem portais que disponibilizam esse recurso como material didático. Um destes portais é o Dia a Dia Educação da Secretaria do Estado do Paraná-SEED. Assim este artigo apresenta uma análise realizada a partir de áudios que estão disponibilizados nesse portal. Nossa intenção foi verificar a funcionalidade e a recepção dos estudantes para este tipo de recurso. As avaliações demonstram que é possível utilizar esse recurso em sala de aula, entretanto é preciso superar algumas dificuldades técnicas impostas pelos recursos tecnológicos oferecidos à professores e estudantes nas escolas do Paraná

A novel experiment for coherent elastic neutrino nucleus scattering:CONUS

The CONUS experiment (COherent elastic NeUtrino nucleus Scattering) aims at detecting coherent elastic neutrino nucleus scattering of reactor antineutrinos on Germanium. The experiment will be set up at the commercial nuclear power plant of Brokdorf, Germany, at a distance of ∼17 m to the reactor core. The recoil of the nuclei hit by the antineutrinos is detected with four high-purity point contact Germanium detectors with a very low threshold and an overall mass of about 4 kg. To suppress the background, the setup is equipped with a shell-like passive shield and an active muon veto system. The shield and the muon veto have successfully been tested at the shallow depth laboratory at Max-Planck-Institut für Kernphysik. Monte Carlo simulations have been performed to reproduce the prompt muon-induced background and to examine the induced neutron spectrum. Currently, the low threshold Germanium detectors are characterized and the experiment is prepared for commissioning.The CONUS experiment (COherent elastic NeUtrino nucleus Scattering) aims at detecting coherent elastic neutrino nucleus scattering of reactor antineutrinos on Germanium. The experiment will be set up at the commercial nuclear power plant of Brokdorf, Germany, at a distance of ∼17 m to the reactor core. The recoil of the nuclei hit by the antineutrinos is detected with four high-purity point contact Germanium detectors with a very low threshold and an overall mass of about 4 kg. To suppress the background, the setup is equipped with a shell-like passive shield and an active muon veto system. The shield and the muon veto have successfully been tested at the shallow depth laboratory at Max-Planck-Institut für Kernphysik. Monte Carlo simulations have been performed to reproduce the prompt muon-induced background and to examine the induced neutron spectrum. Currently, the low threshold Germanium detectors are characterized and the experiment is prepared for commissioning