10 research outputs found
Electric field gradients in MgB synthesized at high pressure: Cd TDPAC study and ab initio calculation
We report the high-pressure synthesis of novel superconductor MgB and
some related compounds. The superconducting transition temperature of our
samples of MgB is equal to 36.6 K. The MgB 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
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 B NMR spectra of MgB reported in the
literature. It is also very close to EFG found in our Cd TDPAC
measurements, which suggests that the Cd probe substitutes for boron in
the MgB 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 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
Results of the BiPo-1 prototype for radiopurity measurements for the SuperNEMO double beta decay source foils
The development of BiPo detectors is dedicated to the measurement of
extremely high radiopurity in Tl and Bi for the SuperNEMO
double beta decay source foils. A modular prototype, called BiPo-1, with 0.8
of sensitive surface area, has been running in the Modane Underground
Laboratory since February, 2008. The goal of BiPo-1 is to measure the different
components of the background and in particular the surface radiopurity of the
plastic scintillators that make up the detector. The first phase of data
collection has been dedicated to the measurement of the radiopurity in
Tl. After more than one year of background measurement, a surface
activity of the scintillators of (Tl) 1.5
Bq/m is reported here. Given this level of background, a larger BiPo
detector having 12 m of active surface area, is able to qualify the
radiopurity of the SuperNEMO selenium double beta decay foils with the required
sensitivity of (Tl) 2 Bq/kg (90% C.L.) with a six
month measurement.Comment: 24 pages, submitted to N.I.M.
The Majorana Neutrinoless Double-Beta Decay Experiment
The proposed Majorana double-beta decay experiment is based on an array of
segmented intrinsic Ge detectors with a total mass of 500 kg of Ge isotopically
enriched to 86% in 76Ge. A discussion is given of background reduction by:
material selection, detector segmentation, pulse shape analysis, and
electro-formation of copper parts and granularity. Predictions of the
experimental sensitivity are given. For an experimental running time of 10
years over the construction and operation of Majorana, a half-life sensitivity
of ~4x10^27 y (neutrinoless) is predicted. This corresponds to an effective
Majorana mass of the electron neutrino of ~0.03-0.04 eV, according to recent
QRPA and RQRPA matrix element calculations.Comment: 10 pages, 7 figure
Measurement of the background in the NEMO 3 double beta decay experiment
In the double beta decay experiment NEMO~3 a precise knowledge of the background in the signal region is of outstanding importance. This article presents the methods used in NEMO~3 to evaluate the backgrounds resulting from most if not all possible origins. It also illustrates the power of the combined tracking-calorimetry technique used in the experiment