The first results of neutron-flux measurements at the LSM underground laboratory (Modane, France) using a new sensitive method are presented. Neutrons are detected by counting delayed γγ coincidences in the 127I(n, γ)128I reaction. It is shown that this approach makes it possible to measure thermal-neutron fluxes at a level of 10–6 neutron cm–2 s–1.

A new experimental run of searching for EC/EC decay of Cd-106 was performed at the Modane underground laboratory (4800 m w.e.) using the TGV-2 spectrometer and similar to 23.2 g Cd-106 with enrichment of 99.57%. The limit on 2 nu EC/EC decay of Cd-106 -T-1/2(2 nu EC/EC) > 3.1x10(20) y, at 90% C. L was obtained from the preliminary calculation of experimental data accumulated for 7018 h of measurement. The limits on the resonance neutrino-less double electron capture decay of Cd-106 were obtained from the measurement of similar to 23.2 g of Cd-106 with the low-background HPGe spectrometer OBELIX lasted 395 h -T-1/2(KL, 2741 keV) > 0.9x10(20) y and T-1/2(KK, 2718 keV) > 1.4x10(20) y at 90% C.L.

A new experiment devoted to searches for double electron capture in 106Cd decay is being performed at the Modane underground laboratory (4800 mwe) with the 32-detector TGV-2 spectrometer. The limit T 1/2(2νEC/EC) > 2.0×1020 yr at a 90%confidence level (C.L.) was obtained from a preliminary analysis of data obtained over 2250 h of measurements with about 23.2 g sample enriched in the isotope 106Cd to 99.57%. The limits T 1/2(KL, 2741 keV) > 0.9 × 1020 yr and T 1/2(KK, 2718 keV) ≫ 1.4 × 1020 yr at a 90% C.L. on the neutrinoless decay of 106Cd were obtained from measurements performed with the Obelix low-background spectrometer from high-purity germanium (HPGe spectrometer) for a sample of mass about 23.2 g enriched in the isotope 106Cd.

The high value of the cross section of thermal neutron capture by the 113 Cd nucleus allows us to regard cadmium-loaded organic scintillators as an alternative to gadolinium-loaded analogues. We report on new plastic and liquid scintillators with maximum metal concentrations of 2 and 1.5 wt %, respectively. Transmission spectra, scintillation characteristics, and efficiencies of the registration of thermal neutrons are given.

We have constructed a GEANT4-based detailed software model of photon transport in plastic scintillator blocks and have used it to study the NEMO-3 and SuperNEMO calorimeters employed in experiments designed to search for neutrinoless double beta decay. We compare our simulations to measurements using conversion electrons from a calibration source of 207Bi and show that the agreement is improved if wavelength-dependent properties of the calorimeter are taken into account. In this article, we briefly describe our modeling approach and results of our studies.

Investigation of double electron capture in 106Cd was performed at the Modane underground laboratory (4800 m.w.e.) using the multi-detector spectrometer TGV-2. In Phase I of the experiment, ∼10 g of 106Cd with an enrichment of 75% was measured during 8687 hours. In Phase II, the TGV-2 background was significantly suppressed in comparison with Phase I and the 106Cd mass was increased to ∼13.6 g. New half-life limits (at 90% CL) were obtained for 2νEC/EC decay of 106Cd to the ground state of Pd106 – T1/2>3.0×1020y (Phase I) and T1/2>3.6×1020y (Phase II, 9000 hours), and for 0νEC/EC decay of 106Cd to the 2741 keV excited state of Pd106 – T1/2>1.1×1020y (Phase II).

The collaboration TGV has finished measurement of 2 nu EC/EC decay of Cd-106 with 10g (Phase I) and 13.6g (Phase II) samples (with enrichment of 75%), respectively. The times of measurements were 8687h (Phase I) and 12900h (Phase II). The half-life limits (at 90% CL) were obtained for 2 nu EC/EC decay of Cd-106 to the ground state of Pd-106 as T-1/2 > 3.0 x 10(20) y (Phase I) and T-1/2 > 4.2 x 10(20) y (Phase II). The collaboration decided to continue with the study of 2 nu EC/EC decay of Cd-106 using 23g of an isotope enriched to 98.4%. We plan to use the TGV II spectrometer for this measurement and also Si pixel detectors for further study of double beta decay (beta beta) processes.

One promising approach to the search for neutrinoless double beta (0ν2β) decay is the use of liquid scintillators with double β-decay sources dissolved in them. The 150Nd isotope is the one best suited to observing this process. Samples of liquid scintillators based on linear alkylbenzene with a neodymium mass fraction of 0.32% are described in this work; neodymium 4-methyloctanoate was used as a Nd-loaded additive. The spectral-luminescent and scintillation properties of the new materials were studied. The possibility of using the obtained compounds in experiments to search for 0ν2β decay is demonstrated.

The results of studies on optimizing the composition of a new liquid scintillator based on linear alkylbenzene are presented. Light yield, transparency, absorption and luminescence spectra are measured. For liquid scintillator samples placed in a 50 × 50 mm Teflon cylindrical cell, the energy resolution measured for 1 MeV electrons (207Bi) was 8%.

Currently, the TGV collaboration is investigating the two-neutrino double electron capture (2 nu EC/EC) of Cd-106 at the Modane underground laboratory. The study is performed with low-background multi-HPGe detector TGV II, which has been constructed for measurements of the rare processes. The half-life limits of T-1/2 > 2.6 x 10(20) years (for Phase I, 8687 hours) and T-1/2 > 3.6 x 10(20) years (for Phase II, 9003 hours) were obtained for the ground state to ground state 2 nu EC/EC of Cd-106. The results already allow to rule out some of the previous nuclear structure calculations.

In the double beta decay experiment NEMO 3 a precise knowledge of the background in the signal region is of outstanding importance. This article presents the methods used in NEMO 3 to evaluate the backgrounds resulting from most if not all possible origins. It also illustrates the power of the combined tracking-calorimetry technique used in the experiment.

The studies aimed at decreasing the background of the TGV-2 spectrometer have led to constructive changes in the cryostat and increased the sensitivity of the 32-detector spectrometer. New search for 0νEC/EC, 2νEC/EC) decays of 106Cd was started with ∼13.6 g of 106Cd with enrichment of 75%. The evaluation of the experimental data accumulated for 4800 h was performed. Limits (at 90% CL) on the half-lives of 0νEC/EC resonant decay of 106Cd to the 2741 keV excited state of 106Pd (T 1/2 ≥ 6.5 × 1019 y) and on t 2νEC/EC decay to the ground state of 106Pd (0+ → 0+, g.s.) (T 1/2 ≥ 1.7 × 1020 y) were obtained. The limits on the other branches of 106Cd decay—2νEC/EC decay to the 2+, 512 keV and 0 1 + , 1334 keV excited states of 106Pd and 2νβ+β+ and 2νβ+ EC decays of 106Cd to the ground and excited states of 106Pd were improved.

The TGV II (Telescope Germanium Vertical) facility is a low background spectrometer operated in Modane Underground Laboratory (France). It aims at the study of double beta electron capture of 106 Cd. The spectrometer is composed of 32 HPGe planar detectors (total mass of Ge ∼3 kg) interleaved with thin-foil samples made of enriched 106 Cd. In 2007 the Phase I of the experiment (1 year measurement) was finished and the new limit on half-life for two-neutrino double electron capture (g.s. → g.s.) of 106 Cd was obtained as 3.2 × 10 20 years. This limit is significantly higher (by almost three orders of magnitude) than those already published. From December 2007 the Phase II of the experiment continues with more enriched material (13.6 grams instead of 8 grams) and with significantly suppressed background of the cryostat.

Search for the β + β + , β + EC , and EC/EC modes of the 106 Cd decay was carried out with the TGV-2 (Telescope Germanium Vertical) low-background multidetector spectrometer installed at the Modane underground laboratory (4800 m w.e.). The measured foil samples ∼50 μm thick and 52 mm in diameter were placed between the entrance windows of the neighboring detectors inside the cryostat. The total measurement time for 10 g of 106 Cd enriched to 75% was 8687 h. New limits (at the 90% confidence level, CL) were obtained for the 106 Cd half-lives against various branches of the decay to the ground state 0 + and excited states 2 + of the 106 Pd daughter nucleus. They are T 1/2 (2νβ + β + ) ≥ 6.0 × 10 19 y, and T 1/2 (2νβ + EC ) ≥ 5.9 × 10 19 y, and T 1/2 (2ν EC/EC ) ≥ 3.0 × 10 20 y for the transitions to the 0 + ground state of 106 Pd; T 1/2 (2νβ + β + ) ≥ 5.7 × 10 19 y, T 1/2 (2νβ + EC ) ≥ 5.9 × 10 19 y, and T 1/2 (2ν EC/EC ) ≥ 4.2 × 10 19 y for the transitions to the 2 + , 512-keV excited state of 106 Pd; and T 1/2 (2ν EC/EC ) ≥ 3.1 × 10 19 y for the transition to the 0 1 + , 1334-keV excited state of 106 Pd.

The TGV II (Telescope Germanium Vertical) facility is a low background spectrometer operated in Modane Underground Laboratory. It aims at the study of double electron capture of 106Cd. The spectrometer is composed of 32 HPGe planar detectors interleaved with thin-foil samples made of 106Cd enriched to 75%. In 2006, the main run of phase I (1 year duration) was terminated yielding a new limit on half-life for two-neutrino double electron capture in 106Cd as 2.0x1020y. The new limit is significantly higher (by almost three orders of magnitude) than those already published.

Search for the β+β+, β+ EC, and EC/EC modes of the 106Cd decay was carried out with the TGV-2 (Telescope Germanium Vertical) low-background multidetector spectrometer installed at the Modane underground laboratory (4800 m w.e.). The measured foil samples ∼50 μm thick and 52 mm in diameter were placed between the entrance windows of the neighboring detectors inside the cryostat. The total measurement time for 10 g of 106Cd enriched to 75% was 8687 h. New limits (at the 90% confidence level, CL) were obtained for the 106Cd half-lives against various branches of the decay to the ground state 0+ and excited states 2+ of the 106Pd daughter nucleus. They are T 1/2(2νβ+β+) ≥ 6.0 × 1019 y, and T 1/2(2νβ+ EC) ≥ 5.9 × 1019 y, and T 1/2(2νEC/EC) ≥ 3.0 × 1020 y for the transitions to the 0+ ground state of 106Pd; T 1/2(2νβ+β+) ≥ 5.7 × 1019 y, T 1/2(2νβ+ EC) ≥ 5.9 × 1019 y, and T 1/2(2νEC/EC) ≥ 4.2 × 1019 y for the transitions to the 2+, 512-keV excited state of 106Pd; and T 1/2(2νEC/EC) ≥ 3.1 × 1019 y for the transition to the 0 1 + , 1334-keV excited state of 106Pd.

The TGV II (Telescope Germanium Vertical) facility is a low background spectrometer operated in Modane Underground Laboratory. It aims at the study of double electron capture of Cd-106. The spectrometer is composed of 32 HPGe planar detectors interleaved with thin-foil samples made of Cd-106 enriched to 75% (total mass about 10 g). In 2006, the main run of phase I (1 year duration) was terminated yielding a new limit on half-life for two-neutrino double electron capture (g.s.-> g.s.) in Cd-106 as 2.0 x 10(20) years. This limit is significantly higher (by almost three orders of magnitude) than those already published.

A search for double electron capture of 106Cd was performed at the Modane Underground Laboratory (4800 m w.e.) using a low-background and high-sensitivity multidetector spectrometer TGV-2 (Telescope Germanium Vertical). New limits on β +/EC, EC/EC decays of 106Cd were obtained from preliminary calculations of experimental data accumulated for 4800 h of measurement of 10 g of 106Cd with enrichment of 75%. They are \(T_{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}}^{2\nu \beta ^ + EC} \) > 9.1 × 1018 yr, \(T_{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}}^{2\nu {{EC} \mathord{\left/ {\vphantom {{EC} {EC}}} \right. \kern-\nulldelimiterspace} {EC}}} \) > 1.9 × 1019 yr for transitions to the first 2+, 511.9 keV excited state of 106Pd, and \(T_{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}}^{2\nu \beta ^ + EC} \) > 1.3 × 1019 yr, \(T_{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}}^{2\nu {{EC} \mathord{\left/ {\vphantom {{EC} {EC}}} \right. \kern-\nulldelimiterspace} {EC}}} \) > 6.2 × 1019 yr for transitions to the ground 0+ state of 106Pd. All limits are given at 90% C.L.