289 research outputs found
Performances and stability of a 2.4 ton Gd organic liquid scintillator target for antineutrino detection
In this work we report the performances and the chemical and physical
properties of a (2 x 1.2) ton organic liquid scintillator target doped with Gd
up to ~0.1%, and the results of a 2 year long stability survey. In particular
we have monitored the amount of both Gd and primary fluor actually in solution,
the optical and fluorescent properties of the Gd-doped liquid scintillator
(GdLS) and its performances as a neutron detector, namely neutron capture
efficiency and average capture time. The experimental survey is ongoing, the
target being continuously monitored. After two years from the doping time the
performances of the Gd-doped liquid scintillator do not show any hint of
degradation and instability; this conclusion comes both from the laboratory
measurements and from the "in-tank" measurements. This is the largest stable
Gd-doped organic liquid scintillator target ever produced and continuously
operated for a long period
Copper electroforming service at Laboratorio Subterráneo de Canfranc
Electroforming of copper can be very effective to obtain high radio-purity copper parts for low-background experiments. To support the construction of experiments at the Laboratorio Subterráneo de Canfranc in Spain, a Copper Electroforming Service (CES) set-up is in operation. In this work the electroforming system is described and results on the radio-purity of parts made are presented
Highly sensitive gamma-spectrometers of GERDA for material screening: Part I
The GERDA experiment aims to search for the neutrinoless double beta-decay of
76Ge and possibly for other rare processes. The sensitivity of the first phase
is envisioned to be more than one order of magnitude better than in previous
neutrinoless double beta-decay experiments. This implies that materials with
ultra-low radioactive contamination need to be used for the construction of the
detector and its shielding. Therefore the requirements on material screening
include high-sensitivity low-background detection techniques and long
measurement times. In this article, an overview of material-screening
laboratories available to the GERDA collaboration is given, with emphasis on
the gamma-spectrometry. Additionally, results of an intercomparison of the
evaluation accuracy in these laboratories are presented.Comment: Featured in: Proceedings of the XIV International Baksan School
"Particles and Cosmology" Baksan Valley, Kabardino-Balkaria, Russia, April
16-21,2007. INR RAS, Moscow 2008. ISBN 978-5-94274-055-9, pp. 228-232; (5
pages, 0 figures
Signal modeling of high-purity Ge detectors with a small read-out electrode and application to neutrinoless double beta decay search in Ge-76
The GERDA experiment searches for the neutrinoless double beta decay of Ge-76
using high-purity germanium detectors enriched in Ge-76. The analysis of the
signal time structure provides a powerful tool to identify neutrinoless double
beta decay events and to discriminate them from gamma-ray induced backgrounds.
Enhanced pulse shape discrimination capabilities of "Broad Energy Germanium"
detectors with a small read-out electrode have been recently reported. This
paper describes the full simulation of the response of such a detector,
including the Monte Carlo modeling of radiation interaction and subsequent
signal shape calculation. A pulse shape discrimination method based on the
ratio between the maximum current signal amplitude and the event energy applied
to the simulated data shows quantitative agreement with the experimental data
acquired with calibration sources. The simulation has been used to study the
survival probabilities of the decays which occur inside the detector volume and
are difficult to assess experimentally. Such internal decay events are produced
by the cosmogenic radio-isotopes Ge-68 and Co-60 and the neutrinoless double
beta decay of Ge-76. Fixing the experimental acceptance of the double escape
peak of the 2.614 MeV photon to 90%, the estimated survival probabilities at
Qbb = 2.039 MeV are (86+-3)% for Ge-76 neutrinoless double beta decays,
(4.5+-0.3)% for the Ge-68 daughter Ga-68, and (0.9+0.4-0.2)% for Co-60 decays.Comment: 27 pages, 17 figures. v2: fixed typos and references. Submitted to
JINS
First array of enriched ZnSe bolometers to search for double beta decay
The R&D activity performed during the last years proved the potential of ZnSe
scintillating bolometers to the search for neutrino-less double beta decay,
motivating the realization of the first large-mass experiment based on this
technology: CUPID-0. The isotopic enrichment in Se, the ZnSe
crystals growth, as well as the light detectors production have been
accomplished, and the experiment is now in construction at Laboratori Nazionali
del Gran Sasso (Italy). In this paper we present the results obtained testing
the first three ZnSe crystals operated as scintillating bolometers, and
we prove that their performance in terms of energy resolution, background
rejection capability and intrinsic radio-purity complies with the requirements
of CUPID-0
A New 76Ge Double Beta Decay Experiment at LNGS
This Letter of Intent has been submitted to the Scientific Committee of the
INFN Laboratori Nazionali del Gran Sasso (LNGS) in March 2004. It describes a
novel facility at the LNGS to study the double beta decay of 76Ge using an
(optionally active) cryogenic fluid shield. The setup will allow to scrutinize
with high significance on a short time scale the current evidence for
neutrinoless double beta decay of 76Ge using the existing 76Ge diodes from the
previous Heidelberg-Moscow and IGEX experiments. An increase in the lifetime
limit can be achieved by adding more enriched detectors, remaining thereby
background-free up to a few 100 kg-years of exposure.Comment: 67 pages, 19 eps figures, 17 tables, gzipped tar fil
Discovery of the Eu decay
We report on the first compelling observation of decay of Eu
to the ground state of Pm. The measurement was performed using a 6.15 g
LiEu(BO) crystal operated as a scintillating bolometer. The Q-value
and half-life measured are: Q = 1948.9 keV, and
T y . The
half-life prediction of nuclear theory using the Coulomb and proximity
potential model are in good agreement with this experimental result
The CUORE cryostat: an infrastructure for rare event searches at millikelvin temperatures
The CUORE experiment is the world's largest bolometric experiment. The
detector consists of an array of 988 TeO2 crystals, for a total mass of 742 kg.
CUORE is presently taking data at the Laboratori Nazionali del Gran Sasso,
Italy, searching for the neutrinoless double beta decay of 130Te. A large
custom cryogen-free cryostat allows reaching and maintaining a base temperature
of about 10 mK, required for the optimal operation of the detector. This
apparatus has been designed in order to achieve a low noise environment, with
minimal contribution to the radioactive background for the experiment. In this
paper, we present an overview of the CUORE cryostat, together with a
description of all its sub-systems, focusing on the solutions identified to
satisfy the stringent requirements. We briefly illustrate the various phases of
the cryostat commissioning and highlight the relevant steps and milestones
achieved each time. Finally, we describe the successful cooldown of CUORE
CUPID-0: the first array of enriched scintillating bolometers for 0decay investigations
The CUPID-0 detector hosted at the Laboratori Nazionali del Gran Sasso, Italy, is the first large array of enriched scintillating cryogenic detectors for the investigation of82Se neutrinoless double-beta decay (0). CUPID-0 aims at measuring a background index in the region of interest (RoI) for 0at the level of 10- 3 counts/(keV kg years), the lowest value ever measured using cryogenic detectors. CUPID-0 operates an array of Zn82Se scintillating bolometers coupled with bolometric light detectors, with a state of the art technology for background suppression and thorough protocols and procedures for the detector preparation and construction. In this paper, the different phases of the detector design and construction will be presented, from the material selection (for the absorber production) to the new and innovative detector structure. The successful construction of the detector lead to promising preliminary detector performance which is discussed here
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