We present a novel approach for the search of dark matter in the DarkSide-50 experiment, relying on Bayesian Networks. This method incorporates the detector response model into the likelihood ...function, explicitly maintaining the connection with the quantity of interest. No assumptions about the linearity of the problem or the shape of the probability distribution functions are required, and there is no need to morph signal and background spectra as a function of nuisance parameters. By expressing the problem in terms of Bayesian Networks, we have developed an inference algorithm based on a Markov Chain Monte Carlo to calculate the posterior probability. A clever description of the detector response model in terms of parametric matrices allows us to study the impact of systematic variations of any parameter on the final results. Our approach not only provides the desired information on the parameter of interest, but also potential constraints on the response model. Our results are consistent with recent published analyses and further refine the parameters of the detector response model.
Abstract Aria is a plant hosting a $${350}\,\hbox {m}$$ 350 m cryogenic isotopic distillation column, the tallest ever built, which is being installed in a mine shaft at Carbosulcis S.p.A., ...Nuraxi-Figus (SU), Italy. Aria is one of the pillars of the argon dark-matter search experimental program, lead by the Global Argon Dark Matter Collaboration. It was designed to reduce the isotopic abundance of $${^{39}\hbox {Ar}}$$ 39 Ar in argon extracted from underground sources, called Underground Argon (UAr), which is used for dark-matter searches. Indeed, $${^{39}\hbox {Ar}}$$ 39 Ar is a $$\beta $$ β -emitter of cosmogenic origin, whose activity poses background and pile-up concerns in the detectors. In this paper, we discuss the requirements, design, construction, tests, and projected performance of the plant for the isotopic cryogenic distillation of argon. We also present the successful results of the isotopic cryogenic distillation of nitrogen with a prototype plant.
The results of comparison of three variants of the form of holes in the pipeline show that the circular hole is the most efficient from the viewpoint of the stress distribution. The process of ...cutting out the hole of this type can be mechanised using a special milling head, which is being developed at present by the Central Scientific Institute of Gas in co-operation with the Central Scientific Research Institute of Heavy Engineering.
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•Planar magnetoelectric voltage transformer fabricated and investigated.•Transformer uses coilless excitation system instead of volumetric magnetic coils.•The voltage transformation ...ratio is magnetically tuned from zero to 13.2.
A planar magnetoelectric voltage transformer based on a layered composite structure containing layers of amorphous ferromagnet and piezoelectric lead zirconate-titanate has been fabricated and investigated. The transformer uses a coilless system (the so-called "magnetic capacitor") to excite the direct magnetoelectric effect at the frequency of the acoustic resonance of the structure, which made it possible to significantly simplify the design. The voltage transformation ratio of the magnetoelectric transformer, in contrast to the known electromagnetic or piezoelectric transformers, can be tuned by an external magnetic field from zero to 13.2 with an increase in the field from zero to 30 Oe. The operating range of the output voltage of the transformer is 0−400 mV, and the output power reaches 9 μW at optimal load resistance. The technique for calculating the characteristics of the transformer is described.
Elongations of magnetoactive elastomers (MAEs) under ascending-descending uniform magnetic fields were studied experimentally using a laboratory apparatus specifically designed to measure large ...extensional strains (up to 20%) in compliant MAEs. In the literature, such a phenomenon is usually denoted as giant magnetostriction. The synthesized cylindrical MAE samples were based on polydimethylsiloxane matrices filled with micrometer-sized particles of carbonyl iron. The impact of both the macroscopic shape factor of the samples and their magneto-mechanical characteristics were evaluated. For this purpose, the aspect ratio of the MAE cylindrical samples, the concentration of magnetic particles in MAEs and the effective shear modulus were systematically varied. It was shown that the magnetically induced elongation of MAE cylinders in the maximum magnetic field of about 400 kA/m, applied along the cylinder axis, grew with the increasing aspect ratio. The effect of the sample composition is discussed in terms of magnetic filler rearrangements in magnetic fields and the observed experimental tendencies are rationalized by simple theoretical estimates. The obtained results can be used for the design of new smart materials with magnetic-field-controlled deformation properties, e.g., for soft robotics.
•Direct and converse magnetoelectric effects observed in flexible FeBSiC-PVDF structure.•Converse ME effect arises due to elastomagnetic nonlinearity of ferromagnetic layer.•Field dependences of ME ...conversion efficiencies are well explained by the theory.
The direct and converse magnetoelectric (ME) effects in a flexible structure containing a mechanically coupled layers of amorphous ferromagnet FeBSiC and a piezo-copolymer poly(viniledene fluoride trifluoroethylen) (P(VDF-TrFE)) are investigated. The mutual transformation of magnetic and electric fields in the structure arises due to a combination of magnetostriction and piezoelectric effects in the ferromagnetic and piezoelectric layer, respectively. The ME effects were induced by exciting the structure with alternating magnetic fields of 0–100 kHz frequency and 1–5 Oe amplitude, or alternating electric fields of amplitudes up to 500 V/cm in the presence of a constant H field. For the direct ME effect the conversion coefficient reached 7.2 V/(cm·Oe) at a bending resonance frequency of 412 Hz and 44 V/(cm·Oe) at a planar resonance frequency of 25.15 kHz. Increasing the excitation magnetic field at the bending resonance frequency, the nonlinear second harmonic generation with an efficiency of 0.24 V/(cm·Oe2) was observed. For the converse ME effect, the conversion coefficient at the planar resonance frequency was 0.09 G·cm/V. The dependences of the efficiencies for the direct and converse ME transformations on the constant field and the amplitudes of the excitation fields are well explained by theory. These results could be used to develop magnetic and electric field sensors, as well as autonomous energy harvesting sources.
•Mixing of electric and magnetic field frequencies was observed in a heterostructure.•Nonlinearity of converse ME effect arises due to nonlinearity of magnetoelasticity.•A theory describing converse ...ME effects in composite structures has been developed.
Nonlinear magnetoelectric effects in a disk-like heterostructure composed of a layer of amorphous ferromagnet (FeBSiC) mechanically coupled to a layer of piezoelectric ceramics (lead zirconate titanate) were studied both experimentally and theoretically. The structure was excited by alternating electrical and magnetic fields far from its acoustic resonance frequency. This induced changes in the magnetic induction within the heterostructure which were recorded using an electromagnetic coil. The experiments were performed for excitations with electric and magnetic fields up to 250 V/cm and 6 Oe, respectively, and bias permanent magnetic fields up to 60 Oe. For large excitation fields, a generation of the second harmonic and harmonics corresponding to the sum and difference frequencies were observed. The coefficient of the frequency doubling for the converse magnetoelectric effect and the coefficient of mixing of electrical and magnetic field frequencies were found to be 4.6∙10−6 G cm2/V2 and ∼1∙10−2 G cm/(Oe∙V), respectively. A simple theoretical model qualitatively describing the experimental findings was proposed. It was shown that the nonlinearity in the converse magnetoelectric effect arises due to the nonlinear dependence of magnetic induction in the ferromagnetic layer on mechanical stress.
Industrial machines and mechanisms, household appliances, natural sources and biological objects generate weak magnetic fields with amplitudes of ~10–12 – 10–4 T in the frequency band of ~1–105Hz. ...Analysis of the fields’ characteristics allows to get information about internal processes and performance of these sources in a non-contact way, to carry out medical diagnostics. This makes topical the development of low-frequency magnetic field spectrum analyzers. The paper describes a spectrum analyzer of a new type using nonlinear effect of magnetic field mixing in a composite ferromagnet-piezoelectric heterostructure. The main element of the analyzer is a magnetic field mixer which contains a piezoelectric langatate single-crystal sandwiched between two layers of a magnetostrictive amorphous alloy. With simultaneous action of the measured magnetic field and the excitation magnetic field on the structure and fulfillment of the frequency matching conditions, the structure generates a voltage at the electromechanical resonance frequency. Swept-tuned spectrum analysis of the measured field is carried out by tuning the frequency of the excitation field. A prototype of the analyzer is fabricated and characterized. It operates in the frequency band of 0.1–85 kHz, has a frequency resolution of ~40 Hz, a minimum detectable field of 50 nT, and a dynamic range of 35 dB. Possibilities to improve characteristics of magnetic field spectrum analyzers are discussed.
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•A new swept-tuned spectrum analyzer of magnetic fields is proposed.•The analyzer uses resonant magnetoelectric effect of magnetic field frequency mixing.•A prototype of the spectrum analyzer is fabricated and characterized.
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