Measurement of the ββ-decay rate of 100Mo to the first excited 0+ state in 100Ru

A new and independent confirmation of ββ(2ν) decay of ¹⁰⁰Mo to the first 0⁺ excited state in ¹⁰⁰Ru has been made. This was accomplished using a two-photon coincidence counting technique in which two HPGe detectors were used to observe the two emitted γrays (E _γ1 = 590.8 keV and E _γ2 = 539.6 keV) from the daughter nucleus as it deexcites to the ground state (0⁺ → 2⁺ → 0⁺). The half-life of this decay has been estimated as ～(5–8)×10²⁰ yr.     

Measurements of events simulating 2β-decay using a nuclear photoemulsion with molybdenum filling

The possibility of neutrinoless double beta decay is studied in the photoemulsion experiment with Mo-100 isotope. The results of measurements of positron-nucleus collisions for the purpose of estimating the background events simulating 2β-decay in the nuclear photoemulsion region adjoining molybdenum conglomerates are presented.     

Phenomenological Study of Solar-Neutrino-Induced ββ Process of 100Mo

The detection of solar-neutrinos of different origin via induced process of ¹⁰⁰Mo is investigated. The particular counting rates and energy distributions of emitted electrons are presented. A discussion in respect to the solar-neutrino detector consisting of 10 tones of ¹⁰⁰Mo is included. Both the cases of the standard solar model and neutrino oscillation scenarios are analyzed. Moreover, new ^-+ and ^-/EC channels of the double-beta process are introduced and possibilities of their experimental observation are addressed.     

β-decay studies of the neutron-rich 18,21N isotopes

The β-decay studies of neutron-rich ^18,21N isotopes have been performed using β-n, β-γ, and β-n-γ coincidence methods. The ^18,21N ions were produced by the fragmentation of the ²²Ne and ²⁶Mg beams, respectively, on a thick beryllium target. The time of flight of the emitted neutrons following the β-decay of ^18,21N was measured by a neutron detector system with wide energy detection range and low-energy detection threshold. In addition, several clover germanium detectors were used to detect the β-delayed γ-rays. The half-lives of the β-decays of ¹⁸N and ²¹N were determined to be (619±2) ms and (82.9±7.5) ms, respectively. Several new β-delayed neutron groups were observed with a total branching ratio of (6.98±1.46)% and (90.5±4.2)% for ¹⁸N and ²¹N, respectively. The level schemes of ¹⁸O and ²¹O were deduced. The experimental Gamow-Teller β-decay strengths of ¹⁸N and ²¹N to these levels were compared with the shell model calculations.     

Structural and physical–chemical properties of the CuGa5Se8, CuGa3Se5 and CuIn3Se5 compounds

Large-block (8×4×3 mm³) CuGa₅Se₈ crystals were obtained by the horizontal Bridgman method. Homogeneous CuGa₃Se₅ and CuIn₃Se₅ single crystals 12 mm in diameter and up to 40 mm in length were grown by directed crystallization of the melt. All three compounds were found to have the chalcopyrite-related structure. The melting points of these compounds were defined by means of the differential thermal analysis. The lattice parameters a and c as well as the axial thermal expansion coefficients α_a and α_c were determined as a function of temperature in the range from 90 to 650 K by the X-ray diffraction method. It is revealed that for all three compounds the coefficients of expansion along the a-axis are larger than those along the c-axis over the entire temperature range studied.     

Study on the selection of BLM detector for C-ADS Injector Ⅱ

The injector of C-ADS (Chinese Accelerator Driven Sub-critical System) project is a high current, fully super-conducting proton accelerator. Meanwhile, a BLM system is indispensable for this facility, especially in low energy segments. This paper presents some basic simulations for 10 MeV proton by Monte Carlo program FLUKA, as well as the distributions on different secondary particles in three aspects: angular, energy spectrum, and current. These results are beneficial to selecting the detector type and its location and determining its dynamic range matching different requirements for both fast and slow beam loss. Furthermore, in this paper the major impact of the background is also analyzed, such as superconducting cavity X radiation and radiation caused by material activation. This work is meaningful in BLM system research.     

Study on the selection of BLM detector for C-ADS Injector Ⅱ

The injector of C-ADS (Chinese Accelerator Driven Sub-critical System) project is a high current, fully super-conducting proton accelerator. Meanwhile, a BLM system is indispensable for this facility, especially in low energy segments. This paper presents some basic simulations for 10 MeV proton by Monte Carlo program FLUKA, as well as the distributions on different secondary particles in three aspects: angular, energy spectrum, and current. These results are beneficial to selecting the detector type and its location and determining its dynamic range matching different requirements for both fast and slow beam loss. Furthermore, in this paper the major impact of the background is also analyzed, such as superconducting cavity X radiation and radiation caused by material activation. This work is meaningful in BLM system research.     

Extrapolation of NEMO Technique to Future Generation of 2β-Decay Experiments

Possibilities of NEMO technique for future neutrinoless double-beta-decay experiments are discussed. Main idea is to have a realistic project with planned sensitivity for half-life on the level (1-2) × 10²⁶ y (sensitivity to neutrino mass (0.05-0.1) eV). It is demonstrated that this can be achieved using improved NEMO technique to investigate 100 kg of ⁸²Se. Possible improvements of NEMO technique and background conditions are discussed. Scheme of future SUPERNEMO detector and main characteristics of experiment are presented. Such detector can be used also to investigate 0 decay in ¹⁰⁰Mo, ¹³⁰Te and ¹¹⁶Cd with sensitivity up to (5-10)×10²⁵ y (or with sensitivity to neutrino mass 0.1 eV).     

Analysis of the Vibrational-Rotational Structure of 2ν1, ν1 + ν3, and 2ν3 Bands of the D2Se Molecule

The absorption spectrum of the D₂Se molecule in the region of 2₁, ₁ + ₃, and 2₃ absorption bands is registered with a high-resolution Fourier spectrometer and is studied theoretically for a Hamiltonian model with allowance for resonant interactions among (200), (101), and (002) vibrational states.     

New phase of the 116Cd 2β-decay experiment with 116CdWO4 scintillators

A new step of the ¹¹⁶Cd 2β-decay experiment is in progress at the Solotvina Underground Laboratory. The upgraded setup consists of four enriched ¹¹⁶CdWO₄ crystal scintillators of total mass 339 g. As an active shield, 15 CdWO₄ crystals (20.6 kg) are used. The background rate (in the energy interval 2.7–2.9 MeV) is 0.06 count/(yr kg keV), one order of magnitude lower than in the previous apparatus. Combined with results of preceding measurements, the half-life limit for the neutrinoless 2β decay of ¹¹⁶Cd to the ground state of ¹¹⁶Sn is determined as T _1/2(0ν)≥5.1×10²² yr with 90% C.L. The limits on T _1/2 for transitions to the excited 2 ₁ ⁺ and 0 ₁ ⁺ levels of ¹¹⁶Sn are 8.6×10²¹ and 4.1×10²¹ yr, respectively (at a 90% C.L.). For 0ν2β decay accompanied by the emission of one and two Majorons, the constraints on the half-life are T _1/2(0νM1)≥1.4×10²¹ yr and T _1/2 (0νM2)≥4.1×10²⁰ yr (at a 90% C.L.). The corresponding constraints on the neutrino mass and the neutrino-Majoron coupling constant are 〈m _v〉 ≤ 3.1 eV and 〈g _M〉 ≤ 1.9 × 10^?4, respectively.     

Muon–hadron detector of the carpet-2 array

The 1-GeV muon–hadron detector of the Carpet-2 multipurpose shower array at the Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences (INR, Moscow, Russia) is able to record simultaneously muons and hadrons. The procedure developed for this device makes it possible to separate the muon and hadron components to a high degree of precision. The spatial and energy features of the muon and hadron extensive-air-shower components are presented. Experimental data from the Carpet-2 array are contrasted against data from the EAS-TOP and KASCADE arrays and against the results of the calculations based on the CORSIKA (GHEISHA + QGSJET01) code package and performed for primary protons and iron nuclei.     

Q value and half-lives for the double-β-decay nuclide 110Pd

The 110Pd double-β decay Q value was measured with the Penning-trap mass spectrometer ISOLTRAP to be Q=2017.85(64) keV. This value shifted by 14 keV compared with the literature value and is 17 times more precise, resulting in new phase-space factors for the two-neutrino and neutrinoless decay modes. In addition a new set of the relevant matrix elements has been calculated. The expected half-life of the two-neutrino mode was reevaluated as 1.5(6)×10(20) yr. With its high natural abundance, the new results reveal 110Pd to be an excellent candidate for double-β decay studies.     

Study of the Defect Structure and Crystal-Field Parameters of α-Al2O3:Yb3+

The methods currently used for studying the defect structure of laser host crystals doped with transition metal or rare-earth ions have several drawbacks or limitations. This study proposes an alternative approach for obtaining optimized impurity structures using molecular dynamics calculation in conjunction with the superposition model. This new approach is specifically applied to a system named α-Al₂O₃:Yb³⁺, in which the simulated defect structure is used to fit the superposition model parameters directly onto the observed energy levels. Such an approach provides predicted values of crystal-field parameters, Zeeman splitting g-factor, and hyperfine structure constants. Moreover, the C_3v site symmetry is found to be a good approximation for the actual C₃ site of Yb³⁺, as doped in an α-Al₂O₃ crystal.     

β-decay studies of the neutron-rich ~(18,21)N isotopes

The β-decay studies of neutron-rich 18,21N isotopes have been performed using β-n, β-γ, and β-n-γ coincidence methods. The 18,21N ions were produced by the fragmentation of the 22Ne and 26Mg beams, respectively, on a thick beryllium target. The time of flight of the emitted neutrons following the β-decay of 18,21N was measured by a neutron detector system with wide energy detection range and low-energy detection threshold. In addition, several clover germanium detectors were used to detect the β-delayed γ-r...     

Identification of the 109Xe and 105Te α-decay chain

The α-decay chain ¹⁰⁹Xe → ¹⁰⁵Te → ¹⁰¹Sn was identified at the Holifield Radioactive Ion Beam Facility. Advances in digital electronics have made possible the identification of both alpha emitters in the same experiment despite the disparate half-lives of 13 ±2 ms and 620 ±70 ns for ¹⁰⁹Xe and ¹⁰⁵Te, respectively. Two α-decay transitions were observed from ¹⁰⁹Xe with Q_α values of 4067 ±10 and 4217 ±8 keV. One transition between the ground states of ¹⁰⁵Te and ¹⁰¹Sn was observed with a Q_α value of 4889 ±6 keV. Using the measured half-lives, branching ratios, and Q_α values the reduced α-decay widths, δ², were determined. Comparison of the δ² value for ¹⁰⁵Te with ²¹³Po indicates a “superallowed" character in the α emission of ¹⁰⁵Te.     

Theβ-decay of100Y: Discovery of a very low lying 0+ state in100Zr

Theβ-decay of¹⁰⁰Y has been investigated at the gas filled recoil separator JOSEF by means ofγ-ray and conversion electron spectroscopy. Twoβ-decay modes, of half lives 0.94±0.03 s and 0.55±0.15 s, have been observed. Using Xγ-, Xce-, γγ- andγce-coincidences the level scheme of¹⁰⁰Zr has been constructed. An excited 0 ₂ ⁺ state at 331.3 keV has been discovered in this nucleus. Theβ-decay from the 0.55 s decay mode in¹⁰⁰Y shows a strong preference for the ground state compared to the 0 ₂ ⁺ state in¹⁰⁰Zr. The structure of¹⁰⁰Zr and the nature of the 0 ₂ ⁺ level is discussed in the light of the present results.