1,551 research outputs found
CdWO4 scintillating bolometer for Double Beta Decay: Light and Heat anticorrelation, light yield and quenching factors
We report the performances of a 0.51 kg CdWO4 scintillating bolometer to be
used for future Double Beta Decay Experiments. The simultaneous read-out of the
heat and the scintillation light allows to discriminate between different
interacting particles aiming at the disentanglement and the reduction of
background contribution, key issue for next generation experiments. We will
describe the observed anticorrelation between the heat and the light signal and
we will show how this feature can be used in order to increase the energy
resolution of the bolometer over the entire energy spectrum, improving up to a
factor 2.6 on the 2615 keV line of 208Tl. The detector was tested in a 433 h
background measurement that permitted to estimate extremely low internal trace
contaminations of 232Th and 238U. The light yield of gamma/beta, alpha and
neutrons is presented. Furthermore we developed a method in order to correctly
evaluate the absolute thermal quenching factor of alpha particles in
scintillating bolometers.Comment: 8 pages 7 figure
An innovative technique for the investigation of the 4-fold forbidden beta-decay of V
For the first time a Vanadium-based crystal was operated as cryogenic
particle detector. The scintillating low temperature calorimetric technique was
used for the characterization of a 22 g YVO crystal aiming at the
investigation of the 4-fold forbidden non-unique decay of V.
The excellent bolometric performance of the compound together with high light
output of the crystal makes it an outstanding technique for the study of such
elusive rate process. The internal radioactive contaminations of the crystal
are also investigated showing that an improvement on the current status of
material selection and purification are needed, U and Th
are measured at the level of 28 mBq/kg, 1.3 Bq/kg and 28 mBq/kg, respectively.
In this work, we also discuss a future upgrade of the experimental set-up which
may pave the road for the detection of the rare V decay
Scintillating double beta decay bolometers
We present the results obtained in the development of scintillating Double
Beta Decay bolometers. Several Mo and Cd based crystals were tested with the
bolometric technique. The scintillation light was measured through a second
independent bolometer. A 140 g CdWO_4 crystal was run in a 417 h live time
measurement. Thanks to the scintillation light, the alpha background is easily
discriminated resulting in zero counts above the 2615 keV gamma line of
Thallium 208. These results, combined with an extremely easy light detector
operation, represent the first tangible proof demonstrating the feasibility of
this kind of technique.Comment: 15 pages, 8 figure
ZnMoO4: a promising bolometer for neutrinoless double beta decay searches
We investigate the performances of two ZnMoO4 scintillating crystals operated
as bolometers, in view of a next generation experiment to search the
neutrinoless double beta decay of Mo-100. We present the results of the alpha
vs beta/gamma discrimination, obtained through the scintillation light as well
as through the study of the shape of the thermal signal alone. The
discrimination capability obtained at the 2615 keV line of Tl-208 is 8 sigma,
using the heat-light scatter plot, while it exceeds 20 sigma using the shape of
the thermal pulse alone. The achieved FWHM energy resolution ranges from 2.4
keV (at 238 keV) to 5.7 keV (at 2615 keV). The internal radioactive
contaminations of the ZnMoO4 crystals were evaluated through a 407 hours
background measurement. The obtained limit is < 32 microBq/kg for Th-228 and
Ra-226. These values were used for a Monte Carlo simulation aimed at evaluating
the achievable background level of a possible, future array of enriched ZnMoO4
crystals.Comment: 9 pages, 8 figure
Two types of all-optical magnetization switching mechanisms using femtosecond laser pulses
Magnetization manipulation in the absence of an external magnetic field is a
topic of great interest, since many novel physical phenomena need to be
understood and promising new applications can be imagined. Cutting-edge
experiments have shown the capability to switch the magnetization of magnetic
thin films using ultrashort polarized laser pulses. In 2007, it was first
observed that the magnetization switching for GdFeCo alloy thin films was
helicity-dependent and later helicity-independent switching was also
demonstrated on the same material. Recently, all-optical switching has also
been discovered for a much larger variety of magnetic materials (ferrimagnetic,
ferromagnetic films and granular nanostructures), where the theoretical models
explaining the switching in GdFeCo films do not appear to apply, thus
questioning the uniqueness of the microscopic origin of all-optical switching.
Here, we show that two different all-optical switching mechanisms can be
distinguished; a "single pulse" switching and a "cumulative" switching process
whose rich microscopic origin is discussed. We demonstrate that the latter is a
two-step mechanism; a heat-driven demagnetization followed by a
helicity-dependent remagnetization. This is achieved by an all-electrical and
time-dependent investigation of the all-optical switching in ferrimagnetic and
ferromagnetic Hall crosses via the anomalous Hall effect, enabling to probe the
all-optical switching on different timescales.Comment: 1 page, LaTeX; classified reference number
Complete elimination of 1K Pot vibrations in dilution refrigerators
Cryogenic vibrations generated by continuously filled 1K Pots are a well known source of noise in all cryogenic experiments using dilution refrigerators. Starting from recent developments we realized a non invasive modification to the cryostat that completely eliminated vibrations, thermalizing the helium coming from the main bath at the pot temperature. We describe the new experimental setup and complete study of the phenomena
Cryogenic light detectors with enhanced performance for rare events physics
We have developed and tested a new way of coupling bolometric light detectors
to scintillating crystal bolometers based upon simply resting the light
detector on the crystal surface, held in position only by gravity. This
straightforward mounting results in three important improvements: (1) it
decreases the amount of non-active materials needed to assemble the detector,
(2) it substantially increases the light collection efficiency by minimizing
the light losses induced by the mounting structure, and (3) it enhances the
thermal signal induced in the light detector thanks to the extremely weak
thermal link to the thermal bath. We tested this new technique with a 16 cm
Ge light detector with thermistor readout sitting on the surface of a large
TeO bolometer. The light collection efficiency was increased by greater
than 50\% compared to previously tested alternative mountings. We obtained a
baseline energy resolution on the light detector of 20~eV RMS that, together
with increased light collection, enabled us to obtain the best vs
discrimination ever obtained with massive TeO crystals. At
the same time we achieved rise and decay times of 0.8 and 1.6 ms, respectively.
This superb performance meets all of the requirements for the CUPID (CUORE
Upgrade with Particle IDentification) experiment, which is a 1-ton
scintillating bolometer follow up to CUORE.Comment: 6 pages, 4 figure
Characterization of ZnSe scintillating bolometers for Double Beta Decay
ZnSe scintillating bolometers are good candidates for future Double Beta
Decay searches, because of the 82Se high Q-value and thanks to the possibility
of alpha background rejection on the basis of the scintillation signal. In this
paper we report the characteristics and the anomalies observed in an extensive
study of these devices. Among them, an unexpected high emission from alpha
particles, accompanied with an unusual pattern of the light vs. heat scatter
plot. The perspectives for the application of this kind of detectors to search
for the Neutrinoless Double Beta Decay of 82Se are presented.Comment: 12 pages, 10 figure
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