23 research outputs found
Search for 2\beta\ decays of 96Ru and 104Ru by ultra-low background HPGe gamma spectrometry at LNGS: final results
An experiment to search for double beta decay processes in 96Ru and 104Ru,
which are accompanied by gamma rays, has been realized in the underground Gran
Sasso National Laboratories of the I.N.F.N. (Italy). Ruthenium samples with
masses of about (0.5-0.7) kg were measured with the help of ultra-low
background high purity Ge gamma ray spectrometry. After 2162 h of data taking
the samples were deeply purified to reduce the internal contamination of 40K.
The last part of the data has been accumulated over 5479 h. New improved half
life limits on 2\beta+/\epsilon \beta+/2\epsilon\ processes in 96Ru have been
established on the level of 10^{20} yr, in particular for decays to the ground
state of 96Mo: T1/2(2\nu 2\beta+) > 1.4 10^{20} yr, T1/2(2\nu \epsilon\beta+) >
8.0 10^{19} yr and T1/2(0\nu 2K) > 1.0 10^{21} yr (all limits are at 90% C.L.).
The resonant neutrinoless double electron captures to the 2700.2 keV and 2712.7
keV excited states of 96Mo are restricted as: T1/2(0\nu KL) > 2.0 10^{20} yr
and T1/2(0\nu 2L) > 3.6 10^{20} yr, respectively. Various two neutrino and
neutrinoless 2\beta\ half lives of 96Ru have been estimated in the framework of
the QRPA approach. In addition, the T1/2 limit for 0\nu 2\beta- transitions of
104Ru to the first excited state of 104Pd has been set as > 6.5 10^{20} yr.Comment: 14 pages, 5 figures, 2 tables; version accepted for publication on
Phys. Rev.
Search for Rare Nuclear Decays with HPGe Detectors at the STELLA Facility of the LNGS
Results on the search for rare nuclear decays with the ultra low background
facility STELLA at the LNGS using gamma ray spectrometry are presented. In
particular, the best T1/2 limits were obtained for double beta processes in
96Ru and 104Ru. Several isotopes, which potentially decay through different
double beta decay channels, including also possible resonant double electron
captures, were investigated for the first time (156Dy, 158Dy, 184Os, 192Os,
190Pt, 198Pt). Search for resonant absorption of solar 7Li axions in a LiF
crystal gave the best limit for the mass of 7Li axions (< 8.6 keV). Rare alpha
decay of 190Pt to the first excited level of 186Os (Eexc = 137.2 keV) was
observed for the first time.Comment: 4 pages, contribution to the MEDEX'13 Conference, corrected list of
author
Low background detector with enriched 116CdWO4 crystal scintillators to search for double beta decay of 116Cd
A cadmium tungstate crystal boule enriched in Cd to 82% with mass of
1868 g was grown by the low-thermal-gradient Czochralski technique. The
isotopic composition of cadmium and the trace contamination of the crystal were
estimated by High Resolution Inductively Coupled Plasma Mass-Spectrometry. The
crystal scintillators produced from the boule were subjected to
characterization that included measurements of transmittance and energy
resolution. A low background scintillation detector with two CdWO
crystal scintillators (586 g and 589 g) was developed. The detector was running
over 1727 h deep underground at the Gran Sasso National Laboratories of the
INFN (Italy), which allowed to estimate the radioactive contamination of the
enriched crystal scintillators. The radiopurity of a third CdWO
sample (326 g) was tested with the help of ultra-low background high purity
germanium detector. Monte Carlo simulations of double
processes in Cd were used to estimate the sensitivity of an experiment
to search for double decay of Cd.Comment: 24 pages, 13 figures, 3 tables, accepted for publication on Journal
of Instrumentatio
Searches for neutrinoless resonant double electron captures at LNGS
Several experiments were performed during last years at underground (3600 m
w.e.) Laboratori Nazionali del Gran Sasso (LNGS) of the INFN (Italy) to search
for resonant 2 captures in 96Ru, 106Cd, 136Ce, 156Dy, 158Dy,
180W, 184Os, 190Pt with the help of HP Ge semiconductor detectors, and ZnWO4
and 106CdWO4 crystal scintillators. No evidence for r-2 decays
was found, and only T_{1/2} limits were established in the range of
10^{14}-10^{21} yr.Comment: Proceedings of TAUP 2011 Conferenc
Refining of Cd and Zn from interstitial impurities using distillation with a ZrFe getter filter
Behavior of interstitial impurities in Cd and Zn is analysed in terms of thermodynamics. The authors consider reduction reactions of cadmium, zinc and carbon oxides, as well as zinc nitride with the getter material from the Zr-Fe alloy, depending on temperature and vacuum. Optimum initial temperature and vacuum conditions for the processes of deep refining of Cd and Zn from interstitial impurities has been developed. It has been shown experimentally that the proposed refining method provides a more effective cleaning of cadmium and zinc from the interstitial impurities than the distillation without a filter: the impurity content is reduced more than tenfold compared to the concentration in the input metal
Production of high purity granular metals: cadmium, zinc, lead
Cadmium, zinc and lead are constituent components of many semiconductor compounds. The obtained high purity distillates and ingots are large-size elements, which is not always convenient to use, and thus require additional grinding, which does not always allow maintaining the purity of the original materials. For the growth of semiconductor and scintillation single crystals it is advisable to use "friable" granular high-purity distillates, which can be processed without the risk of contamination. For example, the European low-background experiment LUCIFER required more than 20 kg of high-purity granulated zinc, which was agreed to be supplied by NSC KIPT. This task was then extended to cadmium and lead.
Motivated by these tasks, the authors of this paper propose complex processes of deep refining of cadmium, zinc and lead by vacuum distillation. A device producing granules has been developed. The process of granulation of high-purity metals is explored.
The purity of produced granules for cadmium and zinc is >99,9999, and >99,9995% for lead granules. To prevent oxidation of metal granules during exposition to air, chemical methods of surface passivation were used. Organic solvent based on dimethylformamide used as a coolant improves the resistance of granules to atmospheric corrosion during the granulation of high purity Cd, Zn and Pb
STUDY OF PLASTIC DEFORMATION OF CADMIUM
The paper presents the results of a study for compression deformation of cadmium samples of different purities at room temperature.The analysis of hardening and recovery processes that influence the formation of the structure in the material is carried out. Conditions for starting work and features of dynamic recovery and dynamic recrystallization in samples of technical and distilled cadmium are considered, which result in softening of the material and grain growth in it. The differences in the course of these processes are determined depending on the purity of the initial samples of cadmium. On the basis of the analysis of changes in acoustic parameters (AE activity, amplitude distribution of signals in the AE spectrum, the contribution of signals of different amplitudes to the integrated spectrum of AE),during deformation, we make assumptions about deformation mechanisms that occur at different stages of cadmium deformation. It is shown that the course of dynamic recovery processes during deformation is much more complicated than static recovery ones after deformation and subsequent annealing
Development and properties of cadmium and lead tungstate low-background scintillators for double beta decay experiments
Methods of deep purification of natural and isotopically enriched cadmium (Cd, 106Cd, 116Cd), as well as of archaeological lead (archPb), to produce cadmium and lead tungstate crystal scintillators have been developed. The basic stages of development and characteristics of the scintillators are described. The developed methods of initial materials purification and crystal growth can be used for the production of scintillators for large-scale high sensitivity experiments to search for rare events (double beta decay, dark matter, rare alpha and beta decay)
CdWO4 crystal scintillators from enriched isotopes for double beta decay experiments
Cadmium tungstate crystal scintillators enriched in 106Cd and 116Cd were
developed. The produced scintillators exhibit good optical and scintillation
properties, and a low level of radioactive contamination. Experiments to
search for double beta decay of 106Cd and 116Cd are in progress at the Gran
Sasso National Laboratories of the INFN (Italy). Prospects to further improve
the radiopurity of the detectors by recrystallization are discussed