763 research outputs found
First Results from the HDMS experiment in the Final Setup
The Heidelberg Dark Matter Search (HDMS) is an experiment designed for the
search for WIMP dark matter. It is using a special configuration of Ge
detectors, to efficiently reduce the background in the low-energy region below
100 keV. After one year of running the HDMS detector prototype in the Gran
Sasso Underground Laboratory, the inner crystal of the detector has been
replaced with a HPGe crystal of enriched Ge. The final setup started
data taking in Gran Sasso in August 2000. The performance and the first results
of the measurement with the final setup are discussed.Comment: 8 pages, revtex, 7 figures, Home Page of Heidelberg Non-Accelerator
Particle Physics Group: http://www.mpi-hd.mpg.de/non_acc
Low level γ-ray germanium-spectrometer to measure very low primordial radionuclide concentrations
Abstract A new germanium spectrometer especially suited for large sample measurements is described in detail. It is operated in the Gran Sasso underground laboratory under shielding rock of 3300 m water equivalent, which reduces the muon flux by six orders of magnitude. The integral background counting rate in the energy range from 50 to 2750 keV is about 0.15 min−1. The low peak count rates of mostly less than 1 count per day together with a relative efficiency of 102% and the high sample capacity makes this spectrometer one of the most sensitive worldwide. Some sample measurements for the solar neutrino experiment BOREXINO and the detector efficiency calibration by the Monte Carlo method are discussed as well
Highly Sensitive Gamma-Spectrometers of GERDA for Material Screening: Part 2
The previous article about material screening for GERDA points out the
importance of strict material screening and selection for radioimpurities as a
key to meet the aspired background levels of the GERDA experiment. This is
directly done using low-level gamma-spectroscopy. In order to provide
sufficient selective power in the mBq/kg range and below, the employed
gamma-spectrometers themselves have to meet strict material requirements, and
make use of an elaborate shielding system. This article gives an account of the
setup of two such spectrometers. Corrado is located in a depth of 15 m w.e. at
the MPI-K in Heidelberg (Germany), GeMPI III is situated at the Gran-Sasso
underground laboratory at 3500 m w.e. (Italy). The latter one aims at detecting
sample activities of the order ~0.01 mBq/kg, which is the current
state-of-the-art level. The applied techniques to meet the respective needs are
discussed and demonstrated by experimental results.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. 233-238; (6
pages, 4 figures
GENIUS-TF: a test facility for the GENIUS project
GENIUS is a proposal for a large scale detector of rare events. As a first
step of the experiment, a small test version, the GENIUS test facility, will be
build up at the Laboratorio Nazionale del Gran Sasso (LNGS). With about 40 kg
of natural Ge detectors operated in liquid nitrogen, GENIUS-TF could exclude
(or directly confirm) the DAMA annual modulation signature within about two
years of measurement.Comment: 14 pages, latex, 5 figures, 3 tables; submitted to Astroparticle
Physic
Background reduction and sensitivity for germanium double beta decay experiments
Germanium detectors have very good capabilities for the investigation of rare
phenomena like the neutrinoless double beta decay. Rejection of the background
entangling the expected signal is one primary goal in this kind of experiments.
Here, the attainable background reduction in the energy region where the
neutrinoless double beta decay signal of 76Ge is expected to appear has been
evaluated for experiments using germanium detectors, taking into consideration
different strategies like the granularity of the detector system, the
segmentation of each individual germanium detector and the application of Pulse
Shape Analysis techniques to discriminate signal from background events.
Detection efficiency to the signal is affected by background rejection
techniques, and therefore it has been estimated for each of the background
rejection scenarios considered. Finally, conditions regarding crystal mass,
radiopurity, exposure to cosmic rays, shielding and rejection capabilities are
discussed with the aim to achieve a background level of 10-3 c keV-1 kg-1 y-1
in the region of interest, which would allow to explore neutrino effective
masses around 40 meV.Comment: 13 pages, 19 figures. Accepted by Astroparticle Physic
Neutron-induced background in the CONUS experiment
CONUS is a novel experiment aiming at detecting elastic neutrino nucleus
scattering in the fully coherent regime using high-purity Germanium (Ge)
detectors and a reactor as antineutrino () source. The detector setup
is installed at the commercial nuclear power plant in Brokdorf, Germany, at a
very small distance to the reactor core in order to guarantee a high flux of
more than 10/(scm). For the experiment, a good
understanding of neutron-induced background events is required, as the neutron
recoil signals can mimic the predicted neutrino interactions. Especially
neutron-induced events correlated with the thermal power generation are
troublesome for CONUS. On-site measurements revealed the presence of a thermal
power correlated, highly thermalized neutron field with a fluence rate of
(74530)cmd. These neutrons that are produced by nuclear
fission inside the reactor core, are reduced by a factor of 10 on
their way to the CONUS shield. With a high-purity Ge detector without shield
the -ray background was examined including highly thermal power
correlated N decay products as well as -lines from neutron
capture. Using the measured neutron spectrum as input, it was shown, with the
help of Monte Carlo simulations, that the thermal power correlated field is
successfully mitigated by the installed CONUS shield. The reactor-induced
background contribution in the region of interest is exceeded by the expected
signal by at least one order of magnitude assuming a realistic ionization
quenching factor of 0.2.Comment: 28 pages, 28 figure
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