Electric field gradients in MgB2_2 synthesized at high pressure: 111^111Cd TDPAC study and ab initio calculation

We report the high-pressure synthesis of novel superconductor MgB$_2$ and some related compounds. The superconducting transition temperature of our samples of MgB$_2$ is equal to 36.6 K. The MgB$_2$ lattice parameters determined via X-ray diffraction are in excellent agreement with results of our ab initio calculations. The time-differential perturbed angular correlation (TDPAC) experiments demonstrate a small increase in quadrupole frequency of $^111$Cd probe with decreasing temperature from 293 to 4.2 K. The electric field gradient (EFG) at the B site calculated from first principles is in fair agreement with EFG obtained from $^11$B NMR spectra of MgB$_2$ reported in the literature. It is also very close to EFG found in our $^111$Cd TDPAC measurements, which suggests that the $^111$Cd probe substitutes for boron in the MgB$_2$ lattice.Comment: 10 pages, 3 figure

Spectral modeling of scintillator for the NEMO-3 and SuperNEMO detectors

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 $\rm ^{207}Bi$ 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.Comment: 16 pages, 10 figure

Investigation of β+^{+}β+^{+}, β+EC, EC/EC decay of 106^{106}Cd with the spectrometer TGV-2

International audienceThe III phase of experiment TGV-2 to search for β$^{+}$β$^{+}$, β+EC, EC/EC decay of $^{106}$Cd was performed at the Modane underground laboratory (LSM, France, 4800 m w.e.). 16 foils (∼23.2 g) of enriched $^{106}$Cd were measured using the 32-detector low background HPGe spectrometer TGV-2 during 42500 h. New limit on 2νEC/EC decay of $^{106}$Cd to the ground 0$^{+}$ state of $^{106}$Pd - T$_{1/2}$ > 7.2 × 10$^{20}$ y at 90% C.L was obtained. The limits on 2νβ$^{+}$β$^{+}$, 2νβ+EC decay of $^{106}$Cd, and 2νECEC decay of $^{106}$Cd to excited states of $^{106}$Pd were significantly improved in comparison with previous phase II of the TGV-2 experiment