561 research outputs found
Production and characterization of a <sup>222</sup>Rn-emanating stainless steel source
Precise radon measurements are a requirement for various applications,ranging from radiation protection over environmental studies to materialscreening campaigns for rare-event searches. All of them ultimately depend onthe availability of calibration sources with a known and stable radon emanationrate. A new approach to produce clean and dry radon sources by implantation ofRa ions into stainless steel has been investigated. In a proof ofprinciple study, two stainless steel plates have been implanted incollaboration with the ISOLDE facility located at CERN. We present results froma complete characterization of the sources. Each sample provides a radonemanation rate of about 2 Bq, which has been measured using electrostatic radonmonitors as well as miniaturized proportional counters. Additional measurementsusing HPGe and alpha spectrometry as well as measurements of the radonemanation rate at low temperatures were carried out.<br
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
Radon daughter removal from PTFE surfaces and its application in liquid xenon detectors
Long-lived radon daughters are a critical background source in experiments
searching for low-energy rare events. Originating from radon in ambient air,
radioactive polonium, bismuth and lead isotopes plate-out on materials that are
later employed in the experiment. In this paper, we examine cleaning procedures
for their capability to remove radon daughters from PTFE surfaces, a material
often used in liquid xenon TPCs. We found a large difference between the
removal efficiency obtained for the decay chains of Rn and Rn,
respectively. This indicates that the plate-out mechanism has an effect on the
cleaning success. While the long-lived Rn daughters could be reduced by
a factor of ~2, the removal of Rn daughters was up to 10 times more
efficient depending on the treatment. Furthermore, the impact of a nitric acid
based PTFE cleaning on the liquid xenon purity is investigated in a small-scale
liquid xenon TPC
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
Statistical Analysis of future Neutrino Mass Experiments including Neutrino-less Double Beta Decay
We perform a statistical analysis with the prospective results of future
experiments on neutrino-less double beta decay, direct searches for neutrino
mass (KATRIN) and cosmological observations. Realistic errors are used and the
nuclear matrix element uncertainty for neutrino-less double beta decay is also
taken into account. Three benchmark scenarios are introduced, corresponding to
quasi-degenerate, inverse hierarchical neutrinos, and an intermediate case. We
investigate to what extend these scenarios can be reconstructed. Furthermore,
we check the compatibility of the scenarios with the claimed evidence of
neutrino-less double beta decay.Comment: Matches published version: Europhys.Lett.85:51002 (2009). Format
changed suitably for ArXi
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
Dark Matter Results from 100 Live Days of XENON100 Data
We present results from the direct search for dark matter with the XENON100
detector, installed underground at the Laboratori Nazionali del Gran Sasso of
INFN, Italy. XENON100 is a two-phase time projection chamber with a 62 kg
liquid xenon target. Interaction vertex reconstruction in three dimensions with
millimeter precision allows to select only the innermost 48 kg as ultra-low
background fiducial target. In 100.9 live days of data, acquired between
January and June 2010, no evidence for dark matter is found. Three candidate
events were observed in a pre-defined signal region with an expected background
of 1.8 +/- 0.6 events. This leads to the most stringent limit on dark matter
interactions today, excluding spin-independent elastic WIMP-nucleon scattering
cross-sections above 7.0x10^-45 cm^2 for a WIMP mass of 50 GeV/c^2 at 90%
confidence level.Comment: 5 pages, 5 figures; matches accepted versio
Implications on Inelastic Dark Matter from 100 Live Days of XENON100 Data
The XENON100 experiment has recently completed a dark matter run with 100.9
live-days of data, taken from January to June 2010. Events in a 48kg fiducial
volume in the energy range between 8.4 and 44.6 keVnr have been analyzed. A
total of three events have been found in the predefined signal region,
compatible with the background prediction of (1.8 \pm 0.6) events. Based on
this analysis we present limits on the WIMP-nucleon cross section for inelastic
dark matter. With the present data we are able to rule out the explanation for
the observed DAMA/LIBRA modulation as being due to inelastic dark matter
scattering off iodine at a 90% confidence level.Comment: 3 pages, 3 figure
Comment on "On the subtleties of searching for dark matter with liquid xenon detectors"
In a recent manuscript (arXiv:1208.5046) Peter Sorensen claims that
XENON100's upper limits on spin-independent WIMP-nucleon cross sections for
WIMP masses below 10 GeV "may be understated by one order of magnitude or
more". Having performed a similar, though more detailed analysis prior to the
submission of our new result (arXiv:1207.5988), we do not confirm these
findings. We point out the rationale for not considering the described effect
in our final analysis and list several potential problems with his study.Comment: 3 pages, no figure
New results on solar neutrino fluxes from 192 days of Borexino data
We report the direct measurement of the ^7Be solar neutrino signal rate
performed with the Borexino detector at the Laboratori Nazionali del Gran
Sasso. The interaction rate of the 0.862 MeV ^7Be neutrinos is
49+-3(stat)+-4(syst) counts/(day * 100ton). The hypothesis of no oscillation
for ^7Be solar neutrinos is inconsistent with our measurement at the 4sigma
level. Our result is the first direct measurement of the survival probability
for solar nu_e in the transition region between matter-enhanced and
vacuum-driven oscillations. The measurement improves the experimental
determination of the flux of ^7Be, pp, and CNO solar nu_e, and the limit on the
magnetic moment of neutrinos
- …