The radioisotope concentrations in stainless steel for the cryostat of the GERDA experiment at the Laboratori Nazionali del Gran Sasso (LNGS) have been measured. A total of 13 different stainless ...steel batches have been screened by low-level
γ
-ray spectrometry with germanium detectors located at two underground laboratories. The article reports the discovery of commonly available stainless steel with very low concentrations of primordial and cosmogenic radionuclides. The concentrations are in the range of 1
mBq/kg and below. Only the manmade
60Co-isotope is present in all samples with a higher concentration of around 19
mBq/kg. Further, deviations from secular equilibrium in the natural decay chains of U and Th have been observed in some cases.
Many extensions of the Standard Model of particle physics explain the dominance of matter over antimatter in our Universe by neutrinos being their own antiparticles. This would imply the existence of ...neutrinoless double-β decay, which is an extremely rare lepton-number-violating radioactive decay process whose detection requires the utmost background suppression. Among the programmes that aim to detect this decay, the GERDA Collaboration is searching for neutrinoless double-β decay of
Ge by operating bare detectors, made of germanium with an enriched
Ge fraction, in liquid argon. After having completed Phase I of data taking, we have recently launched Phase II. Here we report that in GERDA Phase II we have achieved a background level of approximately 10
counts keV
kg
yr
. This implies that the experiment is background-free, even when increasing the exposure up to design level. This is achieved by use of an active veto system, superior germanium detector energy resolution and improved background recognition of our new detectors. No signal of neutrinoless double-β decay was found when Phase I and Phase II data were combined, and we deduce a lower-limit half-life of 5.3 × 10
years at the 90 per cent confidence level. Our half-life sensitivity of 4.0 × 10
years is competitive with the best experiments that use a substantially larger isotope mass. The potential of an essentially background-free search for neutrinoless double-β decay will facilitate a larger germanium experiment with sensitivity levels that will bring us closer to clarifying whether neutrinos are their own antiparticles.
Shielding of the GERDA experiment against external gamma background Barabanov, I.; Bezrukov, L.; Demidova, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2009, Volume:
606, Issue:
3
Journal Article
Peer reviewed
The GERmanium Detector Array (GERDA) experiment will search for neutrinoless double beta decay of Ge76 and is currently under construction at the INFN Laboratori Nazionali del Gran Sasso (LNGS) in ...Italy. The basic design of GERDA is the use of cryogenic liquid and water of high purity as a superior shield against the hitherto dominant background from external gamma radiation. In this paper we show by Monte Carlo simulations and analytical calculations how GERDA was designed to suppress this background at Qββ(Ge76)=2039keV to a level of about 10-4cts/(keVkgy).
Internal contaminations of 238U, 235U and 232Th in the bulk of high purity germanium detectors are potential backgrounds for experiments searching for neutrinoless double beta decay of 76Ge. The data ...from Gerda Phase I have been analyzed for alpha events from the decay chain of these contaminations by looking for full decay chains and for time correlations between successive decays in the same detector. No candidate events for a full chain have been found. Upper limits on the activities in the range of a few nBq/kg for 226Ra, 227Ac and 228Th, the long-lived daughter nuclides of 238U, 235U and 232Th, respectively, have been derived. With these upper limits a background index in the energy region of interest from 226Ra and 228Th contamination is estimated which satisfies the prerequisites of a future ton scale germanium double beta decay experiment.
The background in the 0νββ experiment Gerda Agostini, M.; Allardt, M.; Andreotti, E. ...
The European physical journal. C, Particles and fields,
04/2014, Volume:
74, Issue:
4
Journal Article
Peer reviewed
Open access
The GERmanium Detector Array (
Gerda
) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double beta (
0
ν
β
β
) decay of
76
Ge. The signature of the ...signal is a monoenergetic peak at 2039 keV, the
Q
β
β
value of the decay. To avoid bias in the signal search, the present analysis does not consider all those events, that fall in a 40 keV wide region centered around
Q
β
β
. The main parameters needed for the
0
ν
β
β
analysis are described. A background model was developed to describe the observed energy spectrum. The model contains several contributions, that are expected on the basis of material screening or that are established by the observation of characteristic structures in the energy spectrum. The model predicts a flat energy spectrum for the blinding window around
Q
β
β
with a background index ranging from 17.6 to 23.8
×
10
-
3
cts/(keV kg yr). A part of the data not considered before has been used to test if the predictions of the background model are consistent. The observed number of events in this energy region is consistent with the background model. The background at
Q
β
β
is dominated by close sources, mainly due to
42
K,
214
Bi,
228
Th,
60
Co and
α
emitting isotopes from the
226
Ra decay chain. The individual fractions depend on the assumed locations of the contaminants. It is shown, that after removal of the known
γ
peaks, the energy spectrum can be fitted in an energy range of 200 keV around
Q
β
β
with a constant background. This gives a background index consistent with the full model and uncertainties of the same size.
Radiation hard diamond sensors for future tracking applications Adam, W.; de Boer, W.; Borchi, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2006, Volume:
565, Issue:
1
Journal Article
Peer reviewed
Open access
Progress in experimental particle physics in the coming decade depends crucially upon the ability to carry out experiments in high-radiation areas. In order to perform these complex and expensive ...experiments, new radiation hard technologies must be developed. This paper discusses the use of diamond detectors in future tracking applications and their survivability in the highest radiation environments. We present results of devices constructed with the newest polycrystalline and single crystal Chemical Vapor Deposition diamond and their tolerance to radiation.
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