The NEMO-3 experiment at the Modane Underground Laboratory has investigated the double-\(\beta\) decay of \(^{48}{\rm Ca}\). Using \(5.25\) yr of data recorded with a \(6.99\,{\rm g}\) sample of ...\(^{48}{\rm Ca}\), approximately \(150\) double-\(\beta\) decay candidate events have been selected with a signal-to-background ratio greater than \(3\). The half-life for the two-neutrino double-\(\beta\) decay of \(^{48}{\rm Ca}\) has been measured to be \(T^{2\nu}_{1/2}\,=\,6.4\, ^{+0.7}_{-0.6}{\rm (stat.)} \, ^{+1.2}_{-0.9}{\rm (syst.)} \times 10^{19}\,{\rm yr}\). A search for neutrinoless double-\(\beta\) decay of \(^{48}{\rm Ca}\) yields a null result and a corresponding lower limit on the half-life is found to be \(T^{0\nu}_{1/2} > 2.0 \times 10^{22}\,{\rm yr}\) at \(90\%\) confidence level, translating into an upper limit on the effective Majorana neutrino mass of \(< m_{\beta\beta} > < 6.0 - 26\) \({\rm eV}\), with the range reflecting different nuclear matrix element calculations. Limits are also set on models involving Majoron emission and right-handed currents.
Resonance ionization mass spectrometry (RIMS) is a sensitive and selective method for the determination of extremely low abundances of long-lived radionuclides. The detection limits are about 106 ...atoms per sample and an isotopic selectivity up to 1013 has been achieved. The potential of RIMS using different experimental arrangements is outlined for the determination of isotope ratios and lowest abundances of long-lived radioisotopes of interest like 238–244Pu, 90Sr, and 41Ca. Recent developments in improving detection limits and the spatial resolution of this technique are briefly discussed.
Environmental radioactive particles have assumed in recent years a predominant role for the understanding of the transport mechanisms in the environment as well as for the availability of ...radionuclides to humans. Their characterization by non-destructive instrumental methods can be very useful as applied to radioecological studies. Three specific cases of radioactive environmental particles stemming from different release scenarios are discussed in terms of the information available when characterized by non-destructive spectroscopic methods. In particular, application of SEM-EDX, SIMS and synchrotron-based techniques like μ-XRF, 3D-μ tomography and μ-XANES are considered. The complementarity of the methods is also highlighted.
The NEMO-3 detector, which had been operating in the Modane Underground Laboratory from 2003 to 2010, was designed to search for neutrinoless double $\beta$ ($0\nu\beta\beta$) decay. We report final ...results of a search for $0\nu\beta\beta$ decays with $6.914$ kg of $^{100}$Mo using the entire NEMO-3 data set with a detector live time of $4.96$ yr, which corresponds to an exposure of 34.3 kg$\cdot$yr. We perform a detailed study of the expected background in the $0\nu\beta\beta$ signal region and find no evidence of $0\nu\beta\beta$ decays in the data. The level of observed background in the $0\nu\beta\beta$ signal region $2.8-3.2$ MeV is $0.44 \pm 0.13$ counts/yr/kg, and no events are observed in the interval $3.2-10$ MeV. We therefore derive a lower limit on the half-life of $0\nu\beta\beta$ decays in $^{100}$Mo of $T_{1/2}(0\nu\beta\beta)> 1.1 \times 10^{24}$ yr at the $90\%$ Confidence Level, under the hypothesis of light Majorana neutrino exchange. Depending on the model used for calculating nuclear matrix elements, the limit for the effective Majorana neutrino mass lies in the range $\langle m_{\nu} \rangle < 0.33$--$0.62$ eV. We also report constraints on other lepton-number violating mechanisms for $0\nu\beta\beta$ decays.
Physical Review D 92(2015) 072011 The NEMO-3 detector, which had been operating in the Modane Underground
Laboratory from 2003 to 2010, was designed to search for neutrinoless double
$\beta$ ...($0\nu\beta\beta$) decay. We report final results of a search for
$0\nu\beta\beta$ decays with $6.914$ kg of $^{100}$Mo using the entire NEMO-3
data set with a detector live time of $4.96$ yr, which corresponds to an
exposure of 34.3 kg$\cdot$yr. We perform a detailed study of the expected
background in the $0\nu\beta\beta$ signal region and find no evidence of
$0\nu\beta\beta$ decays in the data. The level of observed background in the
$0\nu\beta\beta$ signal region $2.8-3.2$ MeV is $0.44 \pm 0.13$ counts/yr/kg,
and no events are observed in the interval $3.2-10$ MeV. We therefore derive
a lower limit on the half-life of $0\nu\beta\beta$ decays in $^{100}$Mo of
$T_{1/2}(0\nu\beta\beta)> 1.1 \times 10^{24}$ yr at the $90\%$ Confidence
Level, under the hypothesis of light Majorana neutrino exchange. Depending on
the model used for calculating nuclear matrix elements, the limit for the
effective Majorana neutrino mass lies in the range $\langle m_{\nu} \rangle <
0.33$--$0.62$ eV. We also report constraints on other lepton-number violating
mechanisms for $0\nu\beta\beta$ decays.
Since 1994, IAEA's Marine Environment Laboratory has been assessing the impacts of radioactive-waste dumping in the northwest Pacific Ocean and its marginal seas. The methods used in this assessment ...are described briefly, which have involved the measurement of carbon-14 in seawater samples collected near the dumping sites and in the open ocean. Results from analyses of surface-water samples show relatively low concentrations in the subarctic region at a higher latitude, increasing toward the subtropical region at a median latitude, and decreasing again in the tropical region. High concentrations are found specifically south of the main island of Japan and at a location in the Sea of Japan/East Sea. High super(14)C concentrations in bottom waters are also found at these two sites near Japan.
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