Search

Results of a comparative analysis of the $^{214}$Po ($T_{1/2}= 163.47\pm0.03$ $\mu$s), $^{213}$Po ($T_{1/2}=3.705 \pm 0.001$ $\mu$s) and $^{212}$Po ($T_{1/2}=294.09\pm0.07$ ns) half-life annular variation parameters are presented. It is shown that two independent sequential sets of the $^{214}$Po $\tau$-values $(\tau\equiv T_{1/2})$ obtained in the spaced laboratories can be described by sinusoidal functions. The sinusoid curve with amplitude $A=(5.0 \pm1.5) \cdot 10^{-4}$, period $\omega=(365\pm 8)$ days, and phase $\phi=(170 \pm 7)$ days approximates the set of $^{214}$Po $\tau$ values obtained at BNO INR RAS during the $\sim$973 days starting on January 4, 2012. The function approximates a set of $\tau$-values with a time duration of $\sim1460$ days obtained at the KhNU has an amplitude $A=(4.9\pm1.8)\cdot10^{-4}$, a period $\omega= (377\pm13)$ days and a phase $\phi=(77\pm10)$ days. The $^{213}$Po $\tau$-value set with a time duration of $\sim1700$ days can be described by a sinusoidal function with an amplitude $A=(3.9\pm1.2)\cdot10^{-4}$, a period $\omega= (370\pm13)$ days and a phase $\phi=(130\pm9)$ days. The $^{212}$Po $\tau$-value set with a time duration of $\sim670$ days can be described by a sinusoidal function with an amplitude $A=(7.5\pm1.6)\cdot10^{-4}$, a period $\omega= (375\pm13)$ days and a phase $\phi=(40\pm10)$ days., Comment: 6 pages, 5 figures, Prepared for the proceedings of The 5th International Conference on Particle Physics and Astrophysics (ICPPA-2020)

A device with the parent 229Th source was constructed to search for variations of the daughter 213Po half-life (T1/2 = 4.2 μs). A solar-daily variation with amplitude ASo = (5.3 ± 1.1) × 10–4, a lunar-daily variation with amplitude AL = (4.8 ± 2.1) × 10–4, and a sidereal-daily variation with amplitude AS = (4.2 ± 1.7) × 10–4 were found upon proceeding the data series over a 622-day interval (from July 2015 to March 2017). The 213Po half-life mean value is found to be T1/2 = 3.705 ± 0.001 μs. The reference value is corrected by 12%.

A brief description of the results of joint analysis of data obtained in long-term measurements of krypton samples differing in 78Kr content is presented. Low-background high-pressure proportional gas counters were used as detectors. The comparative analysis of experimental data on single and double K-capture provided the first estimate of the probability of production of a double K-shell vacancy in the process of K-shell electron capture in 81Kr: $${{P}_{{KK}}} = \left[ {5.7 \pm 0.8\,\,({\text{stat}}{\text{.}}) \pm 0.4\,\,({\text{syst}}{\text{.}})} \right] \times {{10}^{{ - 5}}}$$ . A new result for the half-life of 78Kr with respect to the 2K(2ν)-mode was also obtained: $${{T}_{{1/2}}} = \left[ {1.9_{{ - 0.7}}^{{ + 1.3}}\,\,({\text{stat}}{\text{.}}) \pm 0.3\,\,({\text{syst}}{\text{.}})} \right] \times {{10}^{{22}}}$$ years (90% CL).

The results of the experimental search for two-neutrino 2K-capture in 124Xe with a large copper proportional counter obtained by processing the data for an exposure of 37.7 kg day are presented. The experimental setup is located at the Underground Low-Background Laboratory of the Baksan Neutrino Observatory at a depth of 4900 m.w.e. The combination of methods of selection of useful signals with a unique set of characteristics and the event topology taken into account allowed us to suppress the background in the energy region of interest. A new half-life limit for 2K(2ν)-capture in 124Xe was determined: T1/2 ≥ 7.7 × 1021 years (90% CL).

Resonance excitation of the 83Kr first nuclear level (E = 9.4 keV) by solar axions formed via the Primakoff mechanism is sought. The γ- and X-ray photons and the conversion and Auger electrons arising from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory. The following experimental constraint is obtained for the product of the axion–photon coupling constant and the axion mass:|gAγ × mA| ≤ 6.3 × 10 -17 In the framework of the hadronic-axion model, this corresponds to a new axion-mass constraint of mA ≤ 12.7 eV at 95% C.L.

Features of a thermal neutron test detector with thin scintillator [ZnS(Ag)+6LiF] are described. Background of the detector and its registration efficiency were defined as a result of measurements. The thermal neutron flux at different locations, and for different conditions around the Baksan Neutrino Observatory are reported.

The results of investigation of 127Xe radioactive isotope production in the xenon sample enriched in 124Xe, 126Xe, 128Xe are presented. The isotope is supposed to be the source of the background events in the low-background experiment on search for 2K-capture of 124Xe. In this work we consider two channels of 127Xe production: the neutron knock-out from 128Xe nucleus by cosmogenic muons and the neutron capture by 126Xe nucleus. For the first channel the upper limit of the cross section of 127Xe production was found to be σ ≤ 0.007 × 10−24 cm2 at 95% C.L. For the second channel the value obtained for the cross section was found to be equal to σ = (2.74 ± 0.4) × 10−24 cm2, which coincides well, within the statistical error, with reference value.

The results of a search for two neutrino mode of double K-capture of 124Xe using a large copper low-background proportional counter are presented. Data collected during 3220 hours of measurements with 58.6 g of 124Xe provides us to a new limit on the half-life of 124Xe regarding 2K-capture at the level: T1/2 ≥ 2.0 × 1021 years at a 90% confidence level.

We report on the study of thermal neutron flux using monitors based on mixture of ZnS(Ag) and LiF enriched with a lithium-6 isotope at the deep underground laboratory DULB-4900 at the Baksan Neutrino Observatory. An annual modulation of thermal neutron flux in DULB-4900 is observed. Experimental evidences were obtained of correlation between the long-term thermal neutron flux variations and the absolute humidity of the air in laboratory. The amplitude of the modulation exceed 5% of total neutron flux.

Axions with the energy of $$9.4$$ keV emitted in the М1 transition in 83Kr nuclei in the Sun have been searched for using the resonant absorption reaction $$A + \,{{\,}^{{83}}}{\kern 1pt} {\text{Kr}} \to \,{{\,}^{{83}}}{\text{K}}{{{\text{r}}}^{ \star }} \to \,{{\,}^{{83}}}{\kern 1pt} {\text{Kr}} + \gamma ,e$$ (9.4 keV). A krypton-filled proportional counter located in a low-background setup is used to detect $$\gamma $$ rays and electrons. A new limit on the axion–nucleon coupling constant $$\left| {g_{{AN}}^{3} - g_{{AN}}^{0}} \right| \leqslant 8.4 \times {{10}^{{ - 7}}}$$ is obtained. In the hadronic axion model, it leads to a new limit on the axion mass $${{m}_{A}} \leqslant 65$$ eV (95% CL). A possibility of searching for solar axions with 57Fe-containing semiconductor crystals is described.

Axions with energies of 9.4 keV putatively produced in the Sun via an M1-transition in the 83Kr nucleus are searched for using the reaction of resonant absorption: A +83Kr →83Kr* →83Kr + γ, e (9.4 keV). The γ-quanta and electrons are detected with a proportional counter filled with krypton and placed in a low-background setup. A new upper limit on the axion–nucleon coupling constant is imposed: |g AN 3 g AN 0 |≤1.02 106. For the hadronic axion, this implies a new upper limit on the axion mass: m A ≤ 79eV at the 95% confidence level.

The technique used in the experiment in the search for the process of 2K2ν-capture in 124Xe using large high-pressure proportional counters is briefly described. The measurements with a xenon sample enriched to 21% (or ~57 g) of the 124Xe isotope carried out for 3340 hours yielded a zero signal. The resultant upper limit on the 124Xe half-life with respect to the 2ν-mode of the nuclear capture of two K-shell electrons amounts to T 1/2>4.6 1021 yr at the 90% confidence level.

Resonance excitation of the 83Kr first nuclear level (E = 9.4 keV) by solar axions formed via the Primakoff mechanism and via an M1-transition in the 83Kr nucleus in the Sun is searched. The γ-and x-ray photons and the conversion and Auger electrons arising from the excited-level relaxation are detected with a proportional counter in the underground low-background facility of Baksan Neutrino Observatory. The following experimental constraint is obtained for the product of the axion-photon coupling constant and the axion mass: |g Aγ m A | ≼ 6.16 × 10−17. In the framework of the hadronic-axion model, this corresponds to a new axion-mass constraint of mA ≼ 12.6 eV at 95% coincidence level (C.L.). In case of pure hadronic interaction the upper limit for axion-nucleon coupling is | g AN 3 − g AN 0 | ≼ 8.3 × 10−7 at 95% C.L., which corresponds to upper limit for hadrionic axion mass: mA ≼ 64 eV at 95% C.L. with the generally accepted values S = 0.5 and z = 0.56.

The brief description of installation TAU-2 intended for long-term monitoring of the half-life value $\tau$ ($\tau_{1/2}$) of the $^{214}$Po is presented. The methods of measurement and processing of collected data are reported. The results of analysis of time series values $\tau$ with different time step are presented. Total of measurement time was equal to 590 days. Averaged value of the $^{214}$Po half-life was obtained $\tau=163.46\pm0.04$ $\mu$s. The annual variation with an amplitude $A=(8.9\pm2.3)\cdot10^{-4}$, solar-daily variation with an amplitude $A_{So}=(7.5\pm1.2)\cdot10^{-4}$, lunar-daily variation with an amplitude $A_L=(6.9\pm2.0)\cdot10^{-4}$ and sidereal-daily variation with an amplitude $A_S=(7.2\pm1.2)\cdot10^{-4}$ were found in a series of $\tau$ values. The maximal values of amplitude are observed at the moments when the projections of the installation Earth location velocity vectors toward the source of possible variation achieve its maximal magnitudes., Comment: Talk at The International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" February 1 - Ferbuary 8, 2015, Valday,Russia, 7 pages, 12 figure (to be published in PEPAN)

The study of low-yield effects requires not only good quality of the original data but also puts high requirements for their processing procedures to increase the efficiency of the selection of useful events. The exploiting of the large cylindrical proportional counter’s electrostatic topology allows improving the extrapolation of information about the primary ionization of a multipoint event. Long-term calibration measurements with an external 109Cd-source allowed the development of a new method for analyzing the pulse shape from a sizeable proportional counter. Optimized analysis of the current’s pulse shape from the electron cloud of primary ionization in the counter improved the resolution and energy calibration. As a result, the efficiency of selecting useful events was increased by 25%.

We describe the Monte Carlo (MC) simulation package of the `2K-CAPTURE' setup and discuss the agreement of its output with data. The `2K-CAPTURE' MC simulates the energy loss of particles in detector and components of the passive shield and generates the resulting response in working volume large proportional counter (LPC). The simulation accounts for absorption, reemission, and scattering of both photons and neutrons and tracks them until they either are absorbed. The algorithm proceeds with a detailed simulation of the electronics chain. The MC is tuned using data collected with radioactive calibration source deployed in the internal channel of the installation. The simulation reproduces the energy response of the detector corresponding to distribution of the generated pointwise clusters of a charge of primary ionization in LPC., Comment: 6 pages, 5 figures, 1 table, presented at IV international conference on particle physics and astrophysics

Derbin A.V. "Recent results of search for solar axions using resonant absorption by $^{83}$Kr nuclei" in Proceedings of the 13th "Patras" Workshop on Axions, WIMPs and WISPs, PATRAS 2017 / Maroudas, Marios (eds.), Verlag Deutsches Elektronen-Synchrotron : 2018 ; Patras 2017 : 13th Patras Workshop on Axions, WIMPs and WISPs, 2017-05-15 - 2017-05-19, Thessaloniki 13th Patras Workshop on Axions, WIMPs and WISPs, Patras 2017, Thessaloniki, Greece, 15 May 2017 - 19 May 2017; Hamburg : Verlag Deutsches Elektronen-Synchrotron, DESY-PROC, 79-82 (2018). doi:10.3204/DESY-PROC-2017-02/muratova_valentina, 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., Published by Verlag Deutsches Elektronen-Synchrotron, Hamburg

An experimental technique for searching for the 2K capture in 124Xe with a large low-background copper proportional counter is described. Such an experiment is conducted at the Baksan Neutrino Observatory of the Institute for Nuclear Research of the Russian Academy of Sciences. The experimental setup is located in the Low-Background Deep-Level Laboratory at a depth of 4900 m.w.e., where the flux of muons of cosmic rays is suppressed by a factor of 107 relative to that at the Earth’s surface. The setup incorporates a proportional counter and low-background shielding (18 cm of copper, 15 cm of lead, and 8 cm of borated polyethylene). The results of processing the data obtained in 5 months of live measurement time are presented. A new limit on the half-life of 124Xe with respect to the 2K capture is set at the level of 2.5 × 1021 years.

The construction and characteristics of the cylindrical ion pulse ionization chamber (CIPIC) with a working volume of 3.2 L are described. The chamber is intended to register alpha-particles from the $^{222}$Rn and its daughter's decays in the filled air sample. The detector is less sensitive to electromagnetic pick-ups and mechanical noises. The digital pulse processing method is proposed to improve the energy resolution of the ion pulse ionization chamber. An energy resolution of 1.6% has been achieved for the 5.49 MeV alpha-line. The dependence of the energy resolution on high voltage and working media pressure has been investigated and the results are presented., 7 pages, 7 figures, submitted to NIM A

Axions with an energy of 9.4 keV emitted in the M1 transition of 83Kr nuclei in the Sun have been sought in the resonance absorption reaction A + 83Kr → 83Kr* → 83Kr + γ, e (9.4 keV). A proportional gas chamber filled with krypton and placed in a low-background setup at the underground laboratory of the Baksan neutrino observatory was used to detect γ-ray photons and electrons appearing after the decay of a nuclear level. As a result, a new constraint has been determined on the isoscalar and isovector coupling constants of the axion with nucleons: |gAN3– gAN0| ≤ 1.29 × 10–6. This constraint results in the following new bound on the mass of the axion in the hadronic axion model: mA ≤ 100 eV (95% C.L.).

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., Talk at the International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" Jan 26 - Ferb 2, 2014, Valday, Russia, 10 pages, 5 figures

The design changes of the Baksan low-background TAU-1 and TAU-2 set-ups allowed to improve a sensitivity of Po-214 half-life (\tau) measurements up to the 2.5 x 10^{-4} are described. Different possible sources of systematic errors influencing on the $\tau$-value are studed. An annual variation of Po-214 half-life time measurements with an amplitude of A=(6.9 \pm 3) x 10^{-4} and a phase of (\phi=93 \pm 10) days was found in a sequence of the week-collected \tau-values obtained from the TAU-2 data sample with total duration of 480 days. 24 hours' variation of the \tau-value measurements with an amplitude of A=(10.0 \pm 2.6) x 10^{-4} and phase of (\phi=1 \pm 0.5) hours was found in a solar day 1 hour step \tau-value sequence formed from the same data sample. It was found that the Po-214 half-life averaged at 480 days is equal to (163.45 \pm 0.04) mks., Comment: 17 pages, 6 figures, accepted for publication in Journal of Physics of Elementary Particles and Atomic Nuclei

We carried out the comparative study of the signal from the decay of double $K$-shell vacancy production that follows after single $K$-shell electron capture of $^{81}$Kr and double $K$-shell electron capture of $^{78}$Kr. The radiative decay of a the double $1s$ vacancy state was identified by detecting the triple coincidence of two $K$ X-rays and several Auger electrons in the $ECEC$-decay, or by detecting two $K$ X-rays and (Auger electrons + ejected $K$-shell electron) in the $EC$ decay. The number of $K$-shell vacancies per the $K$-electron capture, produced as a result of the shake-off process, has been measured for the decay of $^{81}$Kr. The probability for this decay was found to be $P_{KK}=(5.7\pm0.8)\times10^{-5}$ with a systematic error of $(\Delta P_{KK})_{syst}=\pm0.4 \times10^{-5}$. For the $^{78}{\rm{Kr}}(2\nu2K)$ decay, the comparative study of single- and double-capture decays allowed us to obtain the signal-to-background ratio to be 15/1. The half-life $T_{1/2}^{2\nu2K}(g.s. \rightarrow g.s.) = [1.9^{+1.3}_{-0.7}(stat)\pm0.3(syst)]\times 10^{22}$ y is determined from the analysis of data that have been accumulated over 782 days of live measurements in the experiment that used samples consisted of 170.6 g of $^{78}$Kr., Comment: 17 pages, 9 figures, 1 table

The Baksan Neutrino Observatory (BNO) of Institute for Nuclear Research of the Russian Academy of Science is one of major old underground laboratories in the world for experiments in the field of a nuclear physics, particle and astroparticle physics. A concise technical characteristic of a new lowbackground laboratory DULB-4900 of the BNO is presented. The laboratory is located at a distance of 3700 m from the main entry to the Observatory tunnel, in the hall of 6 6 40 m 3 . Thickness of the mountain rock over DULB corresponds to 4900 m:w:e:, thereby decreasing cosmic ray flux by 10 7 times. The technique and the results of background measurements in the Hall, ordinary box and low-background box are presented. 222 Rn contamination in the laboratory air has been measured by direct detection of -radiation of its daughter 214 Bi distributed over the volume of the lowbackground box. The results of the data analysis are presented.

A brief description of two low-background setups deployed at the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) and intended for searches for two types of double-beta decay of inert-gas isotopes—2K capture on 78Kr and the double-beta decay of 136Xe—is given. The two setups in question have similar structures and employ identical large high-pressure copper proportional counters as detectors. Upon a treatment of data from measurements with krypton samples differing in the content of the isotope 78Kr, the spectrum for an enriched sample revealed an excess of events at a statistical-significance level of about two standard deviations (2σ). If one attributes this excess to 2K(2ν) capture on 78Kr, the respective half-life is T 1/2 = 1.4 −0.7 +2.3 × 1022 yr at a 90% C.L. A treatment of data from measurements with xenon samples differing in content of the isotope 136Xe led to the appearance of an excess of events in the spectrum for an enriched sample at a statistical-significance level of about 2.2σ. If one assumes that this excess is due to the two-neutrino double-beta decay of 136Xe, then the respective half-life is T 1/2 = 5.8 −1.8 +4.7 × 1021 yr.

A scintillating crystal that contains a candidate isotope for DBD provides a promising technique for the high detection-efficiency and good energy resolution. The AMoRE (Advanced Molybdenum based Rare process Experiment) collaboration is studying the potential of CaMoO4 scintillation crystals for searches for looMo 0v DBD.

Scintillation properties and radioactive contamination of calcium molybdate scintillating crystals depleted in 48Ca and enriched in 100Mo (40Ca100MoO4 ) have been studied to prepare a 100Mo-based neutrinoless double beta decay experiment. The prospects of a neutrinoless double beta decay experiment using 40Ca100MoO4 crystals are discussed.

A component analysis of the background of a copper proportional counter with allowance for its input to the parametric region of events due to the expected 2K-capture in 78Kr is presented. The technique of discriminating the simulated events on the edges of the working length of the anode wire is described by comparing the pulse amplitudes of the sought pulse and the first afterpulse in a detector filled with pure krypton without quenchers. The limit on 2K(2ν)-capture for the ground state 78Se (0+ → 0+, g.s.) was found to be T1/2 ≥ 2.4 × 1021 yr (90% confidence level).

A brief description of a setup based on a large-size air ion-pulse ionization chamber intended for monitoring the concentration of 222Rn in the air of laboratories is given. The sensitivity of the detector used for performing measurements with an air sample containing radon with a volume activity of 10 Bq m−3 makes it possible to attain 10% statistical accuracy in determining the area of a radon peak in a measurement time of 103 s. The results from long-term measurements of radon concentration in the air of ground-based and underground laboratories are presented.

The design of a pulse ionization chamber for measuring the surface αactivity of various samples is described. When used together with the appropriate methods for recording and processing the signals, a low-background spectrometer based on this chamber is able to ensure a high sensitivity in direct measurements of ultralow surface α activities. This approach offers a solution to the problem of controlling superpure materials used in detectors for studying rare nuclear processes with a broken equilibrium in the decay chains of the uranium and thorium series. A procedure for modeling the shape of the current pulses according to the orientation of α-particle tracks and their location inside the chamber is described. Results obtained with an α source, as well as with copper and VM2000 light-reflecting film samples, are presented.

The experiment for the 2$\beta$-decay of $^{136}$Xe search with two high-pressure copper proportional counters has been held in Baksan neutrino observatory. The search for the process is based on comparison of spectra measured with natural and enriched xenon. No evidence has been found for 2$\beta$(2$\nu$)- and 2$\beta$(0$\nu$)-decay. The decay half lifetime limit based on data measured during 8000 h is T$_{1/2}$$\geq8.5\cdot10^{21}$yr for 2$\nu$-mode and T$_{1/2}$$\geq3.1\cdot10^{23}$yr for 0$\nu$-mode (90%C.L.)., Comment: 9 pages, 8 figures; talk at the NANP'05 Conference; submitted to Phys. At. Nucl

A technique to search for 2K-capture of $^{78}$Kr with large low-background proportional counter filled with an enriched in $^{78}$Kr up to 99.8% sample of Krypton at a pressure of 4.51 is described in this paper. The results of first measurements are presented. Analysis of data collected during 159 hours yielded new limit to the half-life of $^{78}$Kr with regard to 2K-capture (T$_{1/2}\geq6\cdot10^{21}$ yr (90% C.L.)). Sensitivity of the facility to the process for one year of measurement was evaluated to be $\texttt{S}=1.0\cdot10^{22}$ yr (90% C.L.)., Comment: 4 pages, 5 figures; talk at the NANP'05 Conference; submitted to Phys. At. Nucl

A description of a low-background installation for a new stage of the experimental search for the 2β(2ν) decay of 136Xe with high-pressure copper proportional counters is presented. The first estimate of the decay half-life limit based on the data measured over 4140 h yields T1/2≥2.4×1021 yr (90% C.L.).

The results of amplitude spectrum measurement and data processing of 222Rn and its daughter nucleus decays in a high-pressure copper proportional counter filled with xenon at a pressure of 14.8a tm are given. The preliminary estimates of the α/e ratio for different E/P values are also presented.

The performance characteristics of a proportional counter filled with a gas mixture of Freon-14 (CF4) and Xe at pressures of 0.8–14.8 atm were measured. Adding some Xe (a 1–2% concentration is optimal) to CF4 was found to approximately halve the operating high voltage needed for achieving the same gas-amplification factor as in pure CF4, improve the energy resolution, and increase the expected ultimate gas-amplification factor by an order of magnitude.

First result of experiment for searching of 2K-capture of Xe-124 with the large-volume copper proportional counter is given. The 12 litre sample with 63.3% (44 g) of Xe-124 was used in measurements. The limit on the half-life of Xe-124 with regard to 2K(2��)-capture for the ground state of Te-124 has been found: T_{1/2} > 4.67x10^{20} y (90% C.L.). A sample with volume 52 L comprising of Xe-124 (10.6 L - 58.6 g) and Xe-126 (14.1 L - 79.3 g) will used at the next step of the experiment to increase a sensitivity of 2K-caption of Xe-124 registration. In this case sensitivity to the investigated process will be at the level of S=1.46 x 10^{21} y (90% C.L.) for 1 year measurement., Talk at the International Workshop on Prospects of Particle Physics: "Neutrino Physics and Astrophysics" Jan 26 - Ferb 2, 2014, Valday, Russia, 9 pages, 4 figure and 2 tables

The results of measurements of natural radioactive isotopes content in different source materials of natural and enriched composition used for CaMoO4 scintillation crystal growing are presented. The crystals are to be used in the experiment to search for double neutrinoless betas-decay of Mo-100., Contribution to Proc. of Int. Workshop on Radiopure Scintillators RPSCINT 2013, 17-20.09.2013, Kyiv, Ukraine; to be published in EPJ Web of Conferences; 4 pages, 2 figure and 1 tables

The features of data accumulated for 1817 h in an experimental search for the 2K(2ν)-capture mode of 78Kr decay are discussed. A new limit on the half-life for this decay is found: T1/2≥2.3×1020 yr (at a 90% C.L.).

A pulse shape analysis algorithm and a method for suppressing the noise component of signals from a large copper proportional counter in the experiment aimed at searching for 2K capture of Kr-78 are described. These signals correspond to a compound event with different numbers of charge clusters due to from primary ionization is formed by these signals. A technique for separating single- and multipoint events and determining the charge in individual clusters is presented. Using the Daubechies wavelets in multiresolutional signal analysis, it is possible to increase the sensitivity and the resolution in extraction of multipoint events in the detector by a factor of 3-4., 10 pages, 8 figures. submitted to Instruments and Experimental Techniques; ISSN 0020/4412

AMoRE (Advanced Mo based Rare process Experiment) collaboration is going to use calcium molybdate crystals as cryogenic scintillation detector in a search for neutrinoless DBD of 100Mo isotope. Simultaneous detection of phonons and light will be used to reject internal background. A FWHM resolution of 0.2% in the phonon channel has been achieved with a 0.5 cm3 crystal. Several 40Ca100MoO4 crystals (≈ 0.5 kg) have been developed from enriched 100Mo and depleted 40Ca materials. The light yield of these crystals has been shown to be comparable with reference CaMoO4 scintillators for temperatures ranging down to 8 K. The content of dangerous radioisotopes in the crystals is under measurement. The projected sensitivity of the experiment for a 250 kg × years exposure is lim T1/2 ~ 3 × 1026 years, which corresponds to the effective Majorana neutrino mass mv ~ 0.02 – 0.06 eV.