We present the use of a low background counting facility, equipped with a p-type 80% relative efficiency HPGe detector, protected by active and passive shielding, and large enough to count a 10
in ...photo-multiplier tube (PMT). A GEANT4 Monte-Carlo of this detector was developed and tuned to 3% accuracy. We report the U, Th, and K content in three different types of PMTs used in current neutrino experiments, with accuracies of
∼
10
ppb
for U and Th and of
∼
15
ppm
for K.
We derive the complete set of equations of motion for a suspension of mass-polarized rigid particles in a gravity field. The particles are acted upon by forces and couples exerted by the surrounding ...fluid and by the external gravity field. Besides their mass, momentum, and energy, the particles are characterized by their angular momentum and their (mass) polarization. We discuss the many cross-effects that involve their translational and angular velocities. The balance equations for the fluid phase are obtained from the ensemble average of the local Navier-Stokes equations, while the equations of motion for the particulate phase are obtained by ensemble-averaging the equations for a single particle, much like that in the kinetic theory of gases. We explain why this approach leads to a nonsymmetric stress tensor for the whole suspension, in contrast with the two-fluid approach in which the suspension stress tensor is perfectly symmetric for a suspension of this kind.
We investigate the possible origins of the norm and shape reactor antineutrino anomalies in the framework of a summation model (SM) where $\beta^{-}$ transitions are simulated by a phenomenological ...Gamow-Teller $\beta$-decay strength model. The general trends of the discrepancies to the Huber-Mueller model on the antineutrino side can be reproduced both in norm and shape. From the exact electron-antineutrino correspondence of the SM model, we predict similar distortions in the electron spectra, suggesting that biases on the reference fission-electron spectra could be at the origin of the anomalies.
We propose a simple continuum model to interpret the shearing motion of dense, dry and cohesion-less granular media. Compressibility, dilatancy and Coulomb-like friction are the three basic ...ingredients. The granular stress is split into a rate-dependent part representing the rebound-less impacts between grains and a rate-independent part associated with long-lived contacts. Because we consider stationary flows only, the grain compaction and the grain velocity are the two main variables. The predicted velocity and compaction profiles are in apparent qualitative agreement with most of the experimental or numerical results concerning free-surface shear flows as well as confined shear flows.
The major advances achieved over the last decades in the understanding of fundamental neutrino physics allow us to apply the detection of reactor antineutrino signals to automatic and nonintrusive ...nuclear power plant surveys. Here, we present the NUCIFER experiment, a 1-ton Gd-doped liquid scintillator detector to be installed a few 10 m from a reactor core for measurements of its thermal power and plutonium (Pu) content. The design of such a small volume detector has been focused on high detection efficiency (~ 50% and good background rejection. Detailed simulations of reactor-emitted antineutrino spectrum and detector response have been developed and used to calculate the NUCIFER sensitivity to illicit retrieval of Pu from the core. These results have been presented in October 2008 to the International Atomic Energy Agency (IAEA), which has expressed its interest in the potentialities of this detector as a new safeguard tool.
Coherent elastic neutrino–nucleus scattering (
CE
ν
NS
) offers a unique way to study neutrino properties and to search for new physics beyond the Standard Model. Nuclear reactors are promising ...sources to explore this process at low energies since they deliver large fluxes of anti-neutrinos with typical energies of a few MeV. In this paper, a new-generation experiment to study
CE
ν
NS
is described. The NUCLEUS experiment will use cryogenic detectors which feature an unprecedentedly low-energy threshold and a time response fast enough to be operated under above-ground conditions. Both sensitivity to low-energy nuclear recoils and a high event rate tolerance are stringent requirements to measuring
CE
ν
NS
of reactor anti-neutrinos. A new experimental site, the Very-Near-Site (VNS), at the Chooz nuclear power plant in France is described. The VNS is located between the two 4.25
GW
th
reactor cores and matches the requirements of NUCLEUS. First results of on-site measurements of neutron and muon backgrounds, the expected dominant background contributions, are given. In this paper a preliminary experimental set-up with dedicated active and passive background reduction techniques and first background estimations are presented. Furthermore, the feasibility to operate the detectors in coincidence with an active muon veto at shallow overburden is studied. The paper concludes with a sensitivity study pointing out the physics potential of NUCLEUS at the Chooz nuclear power plant.
A major advance in accurate electron beam polarization measurement has been achieved at Jlab Hall A with a Compton polarimeter based on a Fabry–Perot cavity photon beam amplifier. At an electron ...energy of 4.6
GeV and a beam current of 40
μ
A, a total relative uncertainty of 1.5% is typically achieved within 40
min of data taking. Under the same conditions monitoring of the polarization is accurate at a level of 1%. These unprecedented results make Compton polarimetry an essential tool for modern parity-violation experiments, which require very accurate electron beam polarization measurements.
The STEREO experiment is a very short baseline reactor antineutrino experiment. It is designed to test the hypothesis of light sterile neutrinos being the cause of a deficit of the observed ...antineutrino interaction rate at short baselines with respect to the predicted rate, known as the reactor antineutrino anomaly. The STEREO experiment measures the antineutrino energy spectrum in six identical detector cells covering baselines between 9 and 11 m from the compact core of the ILL research reactor. In this article, results from 179 days of reactor turned on and 235 days of reactor turned off are reported at a high degree of detail. The current results include improvements in the modelling of detector optical properties and the γ-cascade after neutron captures by gadolinium, the treatment of backgrounds, and the statistical method of the oscillation analysis. Using a direct comparison between antineutrino spectra of all cells, largely independent of any flux prediction, we find the data compatible with the null oscillation hypothesis. The best-fit point of the reactor antineutrino anomaly is rejected at more than 99.9% C.L.
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