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E. V. Unzhakov

Publications and source records attributed to E. V. Unzhakov.

At least 19 recordsLinked to original sources
arXiv2025

Electron-antineutrino spectrum from precision measurements of $^{144}$Pr-decay

The $^{144}$Ce -- $^{144}$Pr electron antineutrino source is one of the most suitable radiochemical sources for experiments searching for the oscillations of active neutrinos to the light sterile state. In the current work the $β$-spectra of $^{144}\rm{Ce}$ -- ${^{144}\rm{Pr}}$ source have been measured by two types of $β$-spectrometers based on silicon Si(Li) detectors in order to determine the energy spectrum of electron anti-neutrino emitted in the $β$-decay of $\rm{^{144}Pr}$ nuclei. The nuclear shape factor of the ground state beta transition in ${^{144}\rm{Pr}}-{^{144}\rm{Nd}}$ has been obtained with high precision: $C(W) = 1 + (-0.0301 \pm 0.0007)W + (-0.101 \pm 0.006)W^{-1}$. The reduced cross section for the inverse beta decay reaction on hydrogen for the $\rm{{^{144}Pr}}$ electron anti-neutrino source has been defined as $\rm{(4.7344 \pm 0.0006_{stat} \pm 0.013_{syst}) \times 10^{-44}~cm^2 {decay}^{-1}}$ that provides sufficient sensitivity to search for a sterile neutrino with a mass of $m_4 \sim 1$~eV and a mixing angle $Sin^2(2θ_{14}) \sim 0.005$ using standard disappearance method.

nucl-ex↗
arXiv2023

Investigation of radiation hardness of silicon semiconductor detectors under irradiation with fission products of 252Cf nuclide

Influence of the prolonged irradiation by fission products of 252Cf radionuclide on the operational parameters of silicon-lithium Si(Li) p-i-n detectors, Si surface barrier detectors and Si planar p+n detector was investigated. The obtained results revealed a linear shift of the fission fragment peaks positions towards the lower energies with increase of the irradiation dose for all investigated detectors. The rate of the peaks shift was found to depend strongly on the detector type and the strength of the electric field in the detectors active region, but not on the temperature of irradiation (room or liquid nitrogen temperature). Based on the obtained results, the possibility of integration of the investigated types of Si semiconductor detectors in a radionuclide neutron calibration source is considered.

physics.ins-det↗
arXiv2022

Silicon $4π$ spectrometer for $β$-decay electrons with energies up to 3~MeV

We present a description of the originally developed $β$-spectrometer consisting of two Si(Li)-detectors with sensitive area thickness above 8~mm and $4π$-geometry. The full absorption spectrometer allows for direct measurements of $β$-spectra, disregarding the corrections to the response function induced by the electron backscattering from the crystal surface. In case of $β$-spectra of transitions to the excited state of the daughter isotope additional 3" BGO-detector is used in order to detect the $γ$-quanta in coincidence with the pair of Si(Li)-spectrometers.

physics.ins-det↗
arXiv2021

Influence of α-particles irradiation on the performance and defect levels structure of Al/SiO2/p-type Si surface barrier detector

Deterioration of the operation parameters of Al/SiO2/p-type Si surface barrier detector upon irradiation with alpha-particles at room temperature was investigated. As a result of 40-days irradiation with a total fluence of 8*10^9 α-particles, an increase of α-peak FWHM from 70 keV to 100 keV was observed and explained by increase of the detector reverse current due to formation of a high concentration of near mid-gap defect levels. Performed CV measurements revealed the appearance of at least 6*10^12 cm-3 radiation-induced acceptors at the depths where according to the TRIM simulations the highest concentration of vacancy-interstitial pairs was created by the incoming α-particles. The studies carried out by current-DLTS technique allowed to associate the observed increase of the acceptor concentration with the near mid-gap acceptor level at EV+0.56 eV. This level can be apparently associated with V2O defects recognized previously to be responsible for the space charge sign inversion in the irradiated n-type Si detectors.

physics.ins-det↗
arXiv2021

Precision measurement of $^{\mathbf{210}}$Bi $β$-spectrum

The precision measurement of the $β-$spectrum shape for $^{210}$Bi (historically RaE) have been performed with a spectrometer based on semiconductor Si(Li) detector. This first forbidden non-unique transition has the transition form-factor strongly deviated from unity and knowledge of its spectrum would play an important role in low-background physics in presence of $^{210}$Pb background. The measured transition form-factor could be approximated as $S(W) = 1 + (-0.4363 \pm 0.0037) W + (0.0523 \pm 0.0010) W^2$, that is in good agreement with previous studies and has significantly increased parameter precision.

nucl-ex↗
arXiv2020

New limits on the resonant absorption of solar axions obtained with a $^{169}$Tm-containing cryogenic detector

A search for resonant absorption of solar axions by $^{169}$Tm nuclei was carried out. A newly developed approach involving low-background cryogenic bolometer based on Tm$_3$Al$_5$O$_{12}$ crystal was used that allowed for significant improvement of sensitivity in comparison with previous $^{169}$Tm based experiments. The measurements performed with $8.18$ g crystal during $6.6$ days exposure yielded the following limits on axion couplings: $|g_{Aγ} (g_{AN}^0 + g_{AN}^3) \leq 1.44 \times 10^{-14}$ GeV$^{-1}$ and $|g_{Ae} (g_{AN}^0 + g_{AN}^3) \leq 2.81 \times 10^{-16}$.

hep-ex↗
arXiv2019

A Test of Bolometric Properties of Tm-containing Crystals as a Perspective Detector for the Solar Axion Search

The $^{169}$Tm nuclide has first nuclear level at 8.41 keV with magnetic type transition to the ground state and, therefore, can be used as a target nucleus for the search of resonant absorption of solar axions. We plan to use a Tm-containing crystal of a garnet family Tm$_3$Al$_5$O$_{12}$ as a bolometric detector in order to search for the excitation of the first nuclear level of $^{169}$Tm via the resonant absorption of solar axions. With this perspective in mind, a sample of the Tm$_3$Al$_5$O$_{12}$ crystal was grown and tested for its bolometric and optical properties. Measurements of chemical and/or radioactive contaminations were performed as well. In this paper we present the test results and estimate the requirements for a future low-background experimental setup.

physics.ins-det↗
arXiv2019

Monte-Carlo sensitivity study for sterile neutrino search with $^{144}$Ce - $^{144}$Pr source and liquid scintillation detectors of various geometries

Expected energy spectra calculations for large volume liquid scintillation detectors to inverse $β$-decay for antineutrinos produced by $^{144}$Ce -- $^{144}$Pr artificial source have been performed. The calculations were carried out through Monte-Carlo method within GEANT4.10 framework and were purposed to search for neutrino oscillation to sterile eigenstate with mass about 1 eV. The analysis of relative sensitivity to oscillation parameters for different detector shapes has been performed.

hep-ph↗
arXiv2017

Measurement of $^{144}\rm{Pr}$ beta-spectrum with Si(Li) detectors for the purpose of determining the spectrum of electron antineutrinos

Here we present the specifications of the newly developed beta-spectrometer based on thick full absorption Si(Li) detector. The spectrometer can be used for precision measurements of various beta-spectra, namely for the beta-spectrum shape study of $^{144}$Pr, which is considered to be the most promising anti-neutrino source for sterile neutrino searches.

physics.ins-det↗
arXiv2017

Recent results of search for solar axions using resonant absorption by $^{83}$Kr nuclei

A search for resonant absorption of the solar axion by $^{83}\rm{Kr}$ nuclei was performed using the proportional counter installed inside the low-background setup at the Baksan Neutrino Observatory. The obtained model independent upper limit on the combination of isoscalar and isovector axion-nucleon couplings $|g_3-g_0|\leq 8.4\times 10^{-7}$ allowed us to set the new upper limit on the hadronic axion mass of $m_{A}\leq 65$ eV (95\% C.L.) with the generally accepted values $S$=0.5 and $z$=0.56.

hep-ex↗
arXiv2016

A measurement method of a detector response function for monochromatic electrons based on the Compton scattering

In this paper we present a method of scintillation detector energy calibration using the gamma-rays. The technique is based on the Compton scattering of gamma-rays in a scintillation detector and subsequent photoelectric absorption of the scattered photon in the Ge-detector. The novelty of this method is that the source of gamma rays, the germanium and scintillation detectors are immediately arranged adjacent to each other. The method presents an effective solution for the detectors consisting of a low atomic number materials, when the ratio between Compton effect and photoelectric absorption is large and the mean path of gamma-rays is comparable to the size of the detector. The technique can be used for the precision measurements of the scintillator light yield dependence on the electron energy.

physics.ins-det↗
arXiv2015

New limit on the mass of 9.4-keV solar axions emitted in an M1 transition in $^{83}$Kr nuclei

A search for resonant absorption of the solar axion by $^{83}\rm{Kr}$ nuclei was performed using the proportional counter installed inside the low-background setup at the Baksan Neutrino Observatory. The obtained model independent upper limit on the combination of isoscalar and isovector axion-nucleon couplings $|g_3-g_0|\leq 1.69\times 10^{-6}$ allowed us to set the new upper limit on the hadronic axion mass of $m_{A}\leq 130$ eV (95\% C.L.) with the generally accepted values $S$=0.5 and $z$=0.56.

hep-ex↗
arXiv2014

Search for axioelectric effect of solar axions using BGO scintillating bolometer

A search for axioelectric absorption of solar axions produced in the $ p + d \rightarrow {^3\rm{He}}+γ~(5.5~ \rm{MeV})$ reactions has been performed with a BGO detector placed in a low-background setup. A model-independent limit on an axion-nucleon and axion-electron coupling constant has been obtained: $| g_{Ae}\times g_{AN}^3|< 1.9\times 10^{-10}$ for 90% confidence level. The constrains of the axion-electron coupling have been obtained for hadronic axion with masses in (0.1 - 1) MeV range: $|g_{Ae}| \leq (0.96 - 8.2)\times 10^{-8}$.

hep-ex↗
arXiv2014

First result of the experimental search for the 9.4 keV solar axion reactions with Kr-83 in the copper proportional counter

The experimental search for solar hadronic axions is started at the Baksan Neutrino Observatory of the Institute for Nuclear Researches Russian Academy of Science. It is assumed that axions are created in the Sun during M1-transition between the first thermally excited level at 9.4 keV and the ground state in Kr-83. The experiment is based on axion detection via resonant absorption process by the same nucleus in the detector. The big copper proportional counter filled with krypton is used to detect signals from axions. The experimental setup is situated in the deep underground low background laboratory. No evidence of axion detection were found after the 26.5 days data collection. Resulting new upper limit on axion mass is m_{A} < 130 eV at 95% C.L.

nucl-ex↗
arXiv2013

Search for solar axions produced by Compton process and bremsstrahlung using the resonant absorption and axioelectric effect

The search for resonant absorption of Compton and bremsstrahlung solar axions by $^{169}$Tm nuclei have been performed. Such an absorption should lead to the excitation of low-lying nuclear energy level: $A+^{169}$Tm $\rightarrow ^{169}$Tm$^*$ $\rightarrow ^{169}$Tm $+ γ$ (8.41 keV). Additionally the axio-electric effect in silicon atoms is sought. The axions are detected using a Si(Li) detectors placed in a low-background setup. As a result, a new model independent restrictions on the axion-electron and the axion-nucleon coupling: $g_{Ae}\times|g^0_{AN}+ g^3_{AN}|\leq 2.1\times10^{-14}$ and the axion-electron coupling constant: $|g_{Ae}| \leq 2.2\times 10^{-10}$ has been obtained. The limits leads to the bounds $m_{A}\leq$ 7.9 eV and $m_{A}\leq$ 1.3 keV for the mass of the axion in the DFSZ and KSVZ models, respectively ($90\%$ C.L.).

hep-ex↗
arXiv2011

Constraints on the axion-electron coupling for solar axions produced by Compton process and bremsstrahlung

The search for solar axions produced by Compton ($γ+e^-\rightarrow e^-+A$) and bremsstrahlung-like ($e^-+Z \rightarrow Z+e^-+A$) processes has been performed. The axion flux in the both cases depends on the axion-electron coupling constant. The resonant excitation of low-lying nuclear level of $^{169}\rm{Tm}$ was looked for: $A+^{169}$Tm $\rightarrow ^{169}$Tm$^*$ $\rightarrow ^{169}$Tm $+ γ$ (8.41 keV). The Si(Li) detector and $^{169}$Tm target installed inside the low-background setup were used to detect 8.41 keV $γ$-rays. As a result, a new model independent restriction on the axion-electron and the axion-nucleon couplings was obtained: $g_{Ae}\times|g^0_{AN}+ g^3_{AN}|\leq 2.1\times10^{-14}$. In model of hadronic axion this restriction corresponds to the upper limit on the axion-electron coupling and on the axion mass $g_{Ae}\times m_A\leq3.1\times10^{-7}$ eV (90% c.l.). The limits on axion mass are $m_A\leq$ 105 eV and $m_A\leq$ 1.3 keV for DFSZ- and KSVZ-axion models, correspondingly (90% c.l.).

hep-ex↗
arXiv2009

Search for Resonant Absorption of Solar Axions Emitted in M1 Transition in $^{57}$Fe Nuclei

A search for resonant absorbtion of 14.4 keV solar axions by $^{57}$Fe target was performed. The Si(Li) detector placed inside the low-background setup was used to detect the $γ$-quanta appearing in the deexcitation of 14.4 keV nuclear level: $A+\rm{^{57}Fe} \to \rm{^{57}Fe^{*}} \to \rm{^{57}Fe} + γ$. The new upper limit for the hadronic axion mass have been obtained: $m_{A} \leq 151$ eV (90% C.L.) ($S$=0.5, $z$=0.56).

hep-ex↗