DANSS is a highly segmented 1 m3 plastic scintillator detector. Its 2500 one meter long scintillator strips have a Gd-loaded reflective cover. The DANSS detector is placed under an industrial 3.1 ...GWth reactor of the Kalinin Nuclear Power Plant 350 km NW from Moscow. The distance to the core is varied on-line from 10.7 m to 12.7 m. The reactor building provides about 50 m water-equivalent shielding against the cosmic background. DANSS detects almost 5000 ν˜e per day at the closest position with the cosmic background less than 3%. The inverse beta decay process is used to detect ν˜e. Sterile neutrinos are searched for assuming the 4ν model (3 active and 1 sterile ν). The exclusion area in the Δm142,sin22θ14 plane is obtained using a ratio of positron energy spectra collected at different distances. Therefore results do not depend on the shape and normalization of the reactor ν˜e spectrum, as well as on the detector efficiency. Results are based on 966 thousand antineutrino events collected at three different distances from the reactor core. The excluded area covers a wide range of the sterile neutrino parameters up to sin22θ14<0.01 in the most sensitive region.
We present the first Ge-based constraints on sub-MeV /c2 dark matter (DM) particles interacting with electrons using a 33.4 g Ge cryogenic detector with a 0.53 electron-hole pair (rms) resolution, ...operated underground at the Laboratoire Souterrain de Modane. Competitive constraints are set on the DM-electron scattering cross section, as well as on the kinetic mixing parameter of dark photons down to 1 eV / c2. In particular, the most stringent limits are set for dark photon DM in the 6 to 9 eV / c2 range. These results demonstrate the high relevance of Ge cryogenic detectors for the search of DM-induced eV-scale electron signals.
The DANSS detector (Alekseev et al. in JINST 11:P11011, 2016) is located directly below a commercial reactor core at the Kalinin Nuclear Power Plant. Such a position provides an overburden about 50 ...m.w.e. in vertical direction. In terms of the cosmic rays it occupies an intermediate position between surface and underground detectors. The sensitive volume of the detector is a cubic meter of plastic scintillator with fine segmentation and combined PMT and SiPM readout, surrounded by multilayer passive and active shielding. The detector can reconstruct muon tracks passing through its sensitive volume. The main physics goal of the DANSS experiment implies the antineutrino spectra measurements at various distances from the source. This is achieved by means of a lifting platform so that the data is taken in three positions – 10.9, 11.9 and 12.9 meters from the reactor core. The muon data were collected for nearly four calendar years. The overburden parameters
⟨
E
thr
cos
θ
⟩
and
⟨
E
thr
⟩
, as well as the temperature and barometric correlation coefficients are evaluated separately for the three detector positions and, in each position, in three ranges of the zenith angle – for nearly vertical muons with
cos
θ
>
0.9
, for nearly horizontal muons with
cos
θ
<
0.36
, and for the whole upper hemisphere.
To find a high purity flux for low background experiments is one of the most challenging problems. In this work, we report the production process of a highly purified ammonium acetate flux solution ...for low background experiments. A sub-distilled method has been used to purify initial precursors from contamination for the syntheses of final product. As a result, a high purity ammonium acetate solution was synthesized with a minimum content of elements which collectively represent the main source of background radiation (K < 2.3 × 10
–8
g/g, Th < 2.6 × 10
–11
g/g and U < 1 × 10
–11
g/g). An Estimation of the impurity content of the product has been performed with Instrumental neutron activation analysis, inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry.
High Impedance TES Bolometers for EDELWEISS Marnieros, S.; Armengaud, E.; Arnaud, Q. ...
Journal of low temperature physics,
06/2023, Letnik:
211, Številka:
5-6
Journal Article
Recenzirano
Odprti dostop
The EDELWEISS collaboration aims for direct detection of light dark matter using germanium cryogenic detectors with low threshold phonon sensor technologies and efficient charge readout designs. We ...describe here the development of Ge bolometers equipped with high impedance thermistors based on a Nb
x
Si
1−x
TES alloy. High aspect ratio spiral designs allow the TES impedance to match with JFET or HEMT front-end amplifiers. We detail the behavior of the superconducting transition properties of these sensors and the detector optimization in terms of sensitivity to a-thermal phonons. We report preliminary results of a 200 g Ge detector that was calibrated using
71
Ge activation by neutrons at the LSM underground laboratory.
44Sc is of great interest as a positron emission tomography (PET) radionuclide due to its suitable nuclear characteristics: Eβ+max = 1.47 MeV, branching ratio 94.3% and convenient half-life of ...3.97 h. Here, 44Sc was produced via the widely used reaction 44Ca (p,n)44Sc using natural calcium as a target.
The irradiation was performed at TRIUMF using the 13 MeV cyclotron. The separation consisted of a combination of DGA branched resin and Dowex 50Wx8 (200–400 mesh). The distribution coefficients of Sc3+ on Dowex 50Wx8 (NH4+ form, 200–400 mesh) with ammonium α-hydroxyisobutyrate (pH = 4.8) medium were determined in this study.
The tested scheme allows both a reliable separation of 44Sc from the target material as well as from the other competitive metals and a final fraction with high specific activity. The achieved radiochemical yield was 95 ± 3%.
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The EDELWEISS-II Collaboration has completed a direct search for WIMP dark matter with an array of ten 400-g cryogenic germanium detectors in operation at the Laboratoire Souterrain de Modane. The ...combined use of thermal phonon sensors and charge collection electrodes with an interleaved geometry enables the efficient rejection of γ-induced radioactivity as well as near-surface interactions. A total effective exposure of 384 kg d has been achieved, mostly coming from fourteen months of continuous operation. Five nuclear recoil candidates are observed above 20 keV, while the estimated background is 3.0 events. The result is interpreted in terms of limits on the cross-section of spin-independent interactions of WIMPs and nucleons. A cross-section of 4.4×10−8 pb is excluded at 90%CL for a WIMP mass of 85 GeV. New constraints are also set on models where the WIMP-nucleon scattering is inelastic.
An anion-exchange resin (Dowex 1×8) and a cation-exchange resin (Dowex 50W×8) were used for the determination of the distribution coefficients (K
d
) for the following elements: Sr, Cd, Ba, Ra, Sc, ...Y, Pm, Lu, Ac, Ti, Zr, Hf, Th, As, Sb, and Se in acetic acid media. Concentration of acetic acid was expanded down to 0.01 M and the distribution coefficients on the ion-exchange resins for the elements with valences from II to VI were determined. Furthermore, the K
d
values for a mixtures of acetic acid and ammonium acetate were obtained. Accumulated data is important for more efficient separations and purifications of these elements in the future.
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