Evidence for Coexisting Shapes through Lifetime Measurements in

The lifetimes of the first excited 2^{+}, 4^{+}, and 6^{+} states in ^{98}Zr were measured with the recoil-distance Doppler shift method in an experiment performed at GANIL. Excited states in ^{98}Zr were populated using the fission reaction between a 6.2 MeV/u ^{238}U beam and a ^{9}Be target. The γ rays were detected with the EXOGAM array in correlation with the fission fragments identified by mass and atomic number in the VAMOS++ spectrometer. Our result shows a very small B(E2;2_{1}^{+}→0_{1}^{+}) value in ^{98}Zr, thereby confirming the very sudden onset of collectivity at N=60. The experimental results are compared to large-scale Monte Carlo shell model and beyond-mean-field calculations. The present results indicate the coexistence of two additional deformed shapes in this nucleus along with the spherical ground state.

The Mobile Analyzer of Radioactive Gases OuTflows (MARGOT): A promising environmental xenon radionuclides detection system.

An ultra-compact and unshielded spectrometer for analysis of atmospheric xenon radionuclides has been developed: the MARGOT system. This system works at ambient temperature and high pressure, and has a 54.3 cm3 inner active volume. Atmospheric xenon radionuclide activities are determined with the electron-photon coincidence technique using both NaI(Tl) detectors and large pixellized Si-PIN detectors. The MARGOT system integrates an enhanced version of the PIPSBox™, Geant4 simulation and first calibration results are discussed.

Introducing the MARGOT prototype: An ultra-compact and mobile gas detection system for nuclear explosion monitoring.

An ultra-compact and unshielded spectrometer for analysis of atmospheric radioxenons has been developed. This system works at ambient temperature and has a 58 cm3 inner active volume. Atmospheric radioxenons activities are determined with electron/photon coincidence technique using both NaI(Tl) detector and large pixellized Si-PIN detector. The performances of the detection system without shielding in terms of Minimal Detectable Activities are below 65 mBq for a 12 h acquisition, for all radioxenons of interest. An enhanced version of the prototype presented here is already under development: the Mobile Analyzer for Radioactive Gases OuTflows (MARGOT) system.

Low-level laboratory measurement of xenon radionuclides: Electron-photon versus photon measurements.

Radioactive xenon (mainly 131mXe, 133Xe, 133mXe and 135Xe) are tracked as markers of nuclear weapons testing. The CEA has developed the PIPSBox, a measurement cell able to detect electrons emitted by xenon nuclides. Combined with an ultra-low background γ spectrometer, electron detection capacities allow reaching minimum detectable activities (MDA) for a 3-day long measurement of about 0.5mBq for the four xenon radionuclides. Compared to a classical measurement cell, MDAs are improved by a factor of 2-4.

SPALAX NG: A breakthrough in radioxenon field measurement.

Lessons-learned from 10 years of noble gas stations operation and dedicated R&D allowed the design of a New Generation of station. In order to produce 60m3 air equivalent Xenon samples every 8h, it implements: (i) larger sampler unit for Xenon extraction (2 compressors and 8 nitrogen membranes), (ii) new noble gas adsorbent (Ag@ZSM5), (iii) hardened components and (iv) new high resolution coincidence low background spectrometer (HPGe/PIPSBox). Station expected radioxenon sensitivity is lower than 0.3mBq/m3.

Ground surface ultralow background spectrometer: Active shielding improvements and coincidence measurements for the Gamma3 spectrometer.

The ultralow background versatile spectrometer GAMMA3 has been optimized with the following shielding improvements: (i) optimized nitrogen injection flux of 300Lh-1, and (ii) cosmic veto configuration with 9 scintillating plates. These improvements allow a reduction of 39% of the normalized integral background count rate down to 2.7±0.2min-1kgGe-1 (40-2500keV energy range). Minimum Detectable Activities when performing direct γ-ray spectrometry or γ-γ coincidence spectrometry are compared.