Background:
Between 2008 and 2017, EDF has progressively replaced its old Personal Contamination Monitors (PCM) with a new generation to strengthen the control of the workers at the exit of the ...restricted controlled areas. One of the novelties of the new PCM generation is the introduction of gamma channels which, coupled to the beta channel, allows a more reliable and more precise measurement. The new PCM also includes a better monitoring of the C2 portals alarms triggering system, a greater detection surface to minimize the dead zone and carries out morphological compensation to take into account the attenuation of the gamma background by the body. This new PCM is very efficient and capable of detecting low contamination activities. The sensitivity of this monitoring system is such that the solid progeny of
222
Rn deposited on clothes (such as the
214
Pb and the
214
Po) could in some cases be detected and triggered the C2 portals alarm.
Objective:
In order to quantify the impact of radon (
222
Rn) and its progeny on the C2 portals triggers, a specific study has been conducted. Beyond the physical aspect, several purposes are targeted: (1) to provide quantitative explanations about the C2 alarms attributed to radon and determine which channels are more affected by the
222
Rn progeny; (2) to determine the existence of a relation between C2 alarms and high
222
Rn volume activity; (3) to optimize practices at the exit of the Restricted Controlled Areas (RCA), for example, adapt waiting time before control in PCM. The study consisted in measuring the activity of radon progeny deposited on several types of suits used in EDF Nuclear Power Plants (NPPs). To assess the impact of the
222
Rn, several factors have been studied such as the
222
Rn exposure time, the
222
Rn concentration and the nature of textile fibers constituting clothes. For this study, several facilities from the Laboratoire de Physique des deux infinis de Bordeaux (LP2i Bordeaux) have been used, including a
222
Rn emanation standard source and various emanation chambers between 60 L and 750 L. A specific calibration method to characterize radon progenies deposited has been developed (see Sects. 2.4 and 3). The
222
Rn concentration in the sample exposure environment is verified both using a commercial (see Sects. 2.4 and 3) and experimental high sensitivity radon detectors. The measurements of the
222
Rn progeny on clothes are made immediately after exposure by gamma spectrometry control on a High Purity Germanium (HPGe) detector. This experiment has been carried out at the PRISNA measurement platform (Plateforme Régionale Interdisciplinaire de Spectrométrie Nucléaire en Aquitaine) located in LP2I Bordeaux.
Conclusions:
In this study, several phenomena have been highlighted for a better understanding of the C2 portal triggering. We validate that in presence of
222
Rn volume concentration activity lower than 300 Bq/m
3
, an alarm in beta channels of C2 portals can be triggered because of the presence of the radon progeny on clothes. The triggering of the gamma channels could appear only if the volume concentration activity of radon is higher than 3000 Bq/m
3
. The results obtained in this study could led to optimize and harmonize the practices at the exit of Restricted Controlled Area (RCA) like adapt waiting time before control in PCM.
SuperNEMO is the successor of the NEMO-3 experiment and will search for the hypothetical process of 0νββ by combining tracking and calorimetric measurements. The SuperNEMO calorimeter consists of 712 ...optical modules made of scintillator blocks directly coupled to photomultiplier tubes. 207Bi sources will be used to calibrate the energy scale of the calorimeter in dedicated calibration runs separated by a few weeks. In between these runs, a Light Injection (LI) system will guarantee the stability of the calorimetric response to 1%. The LI system injects pulsed LED light into each scintillator block via optical fibers. A reference optical module is used to monitor the light level against a 241Am source. The details of the LI system and its performance are presented.
The full data set of the NEMO-3 experiment has been used to measure the half-life of the two-neutrino double beta decay of Formula omittedMo to the ground state of Formula omittedRu, Formula omitted ...year. The two-electron energy sum, single electron energy spectra and distribution of the angle between the electrons are presented with an unprecedented statistics of Formula omitted events and a signal-to-background ratio of Formula omitted 80. Clear evidence for the Single State Dominance model is found for this nuclear transition. Limits on Majoron emitting neutrinoless double beta decay modes with spectral indices of Formula omitted, as well as constraints on Lorentz invariance violation and on the bosonic neutrino contribution to the two-neutrino double beta decay mode are obtained.
Abstract The full data set of the NEMO-3 experiment has been used to measure the half-life of the two-neutrino double beta decay of $$^{100}$$ 100 Mo to the ground state of $$^{100}$$ 100 Ru, ...$$T_{1/2} = \left 6.81 \pm 0.01\,\left( \text{ stat }\right) ^{+0.38}_{-0.40}\,\left( \text{ syst }\right) \right \times 10^{18}$$ T1/2=6.81±0.01stat-0.40+0.38syst×1018 year. The two-electron energy sum, single electron energy spectra and distribution of the angle between the electrons are presented with an unprecedented statistics of $$5\times 10^5$$ 5×105 events and a signal-to-background ratio of $$\sim $$ ∼ 80. Clear evidence for the Single State Dominance model is found for this nuclear transition. Limits on Majoron emitting neutrinoless double beta decay modes with spectral indices of $$\mathrm{n}=2,3,7$$ n=2,3,7 , as well as constraints on Lorentz invariance violation and on the bosonic neutrino contribution to the two-neutrino double beta decay mode are obtained.
Calorimeter development for the SuperNEMO double beta decay experiment Barabash, A.S.; Basharina-Freshville, A.; Blot, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2017, Letnik:
868, Številka:
C
Journal Article
Recenzirano
Odprti dostop
SuperNEMO is a double-β decay experiment, which will employ the successful tracker–calorimeter technique used in the recently completed NEMO-3 experiment. SuperNEMO will implement 100 kg of double-β ...decay isotope, reaching a sensitivity to the neutrinoless double-β decay (0νββ) half-life of the order of 1026 yr, corresponding to a Majorana neutrino mass of 50–100 meV. One of the main goals and challenges of the SuperNEMO detector development programme has been to reach a calorimeter energy resolution, ΔE∕E, around 3%∕E(MeV)σ, or 7%∕E(MeV) FWHM (full width at half maximum), using a calorimeter composed of large volume plastic scintillator blocks coupled to photomultiplier tubes. We describe the R&D programme and the final design of the SuperNEMO calorimeter that has met this challenging goal.
The double-beta decay of 82Se to the 01+ excited state of 82Kr has been studied with the NEMO-3 detector using 0.93 kg of enriched 82Se measured for 4.75 y, corresponding to an exposure of 4.42 kg⋅y. ...A dedicated analysis to reconstruct the γ-rays has been performed to search for events in the 2e2γ channel. No evidence of a 2νββ decay to the 01+ state has been observed and a limit of T1/22ν(Se82,0gs+→01+)>1.3×1021y at 90% CL has been set. Concerning the 0νββ decay to the 01+ state, a limit for this decay has been obtained with T1/20ν(Se82,0gs+→01+)>2.3×1022y at 90% CL, independently from the 2νββ decay process. These results are obtained for the first time with a tracko-calo detector, reconstructing every particle in the final state.
The full data set of the NEMO-3 experiment has been used to measure the half-life of the two-neutrino double beta decay of
100
Mo to the ground state of
100
Ru,
T
1
/
2
=
6.81
±
0.01
stat
-
0.40
+
...0.38
syst
×
10
18
year. The two-electron energy sum, single electron energy spectra and distribution of the angle between the electrons are presented with an unprecedented statistics of
5
×
10
5
events and a signal-to-background ratio of
∼
80. Clear evidence for the Single State Dominance model is found for this nuclear transition. Limits on Majoron emitting neutrinoless double beta decay modes with spectral indices of
n
=
2
,
3
,
7
, as well as constraints on Lorentz invariance violation and on the bosonic neutrino contribution to the two-neutrino double beta decay mode are obtained.
Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay ( Formula omitted) half-life of Formula omittedSe as Formula omitted y under the single-state dominance ...hypothesis for this nuclear transition. The corresponding nuclear matrix element is Formula omitted. In addition, a search for neutrinoless double beta decay ( Formula omitted) using 0.93 kg of Formula omittedSe observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of Formula omitted for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of Formula omitted, where the range reflects Formula omitted nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other Formula omitted mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.
Here, using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay (2νββ) half-life of 82Se as T2ν1/2=9.39±0.17( stat )±0.58( syst )×1019 y under the single-state ...dominance hypothesis for this nuclear transition.
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