98 research outputs found
The Borexino detector at the Laboratori Nazionali del Gran Sasso
Borexino, a large volume detector for low energy neutrino spectroscopy, is
currently running underground at the Laboratori Nazionali del Gran Sasso,
Italy. The main goal of the experiment is the real-time measurement of sub MeV
solar neutrinos, and particularly of the mono energetic (862 keV) Be7 electron
capture neutrinos, via neutrino-electron scattering in an ultra-pure liquid
scintillator. This paper is mostly devoted to the description of the detector
structure, the photomultipliers, the electronics, and the trigger and
calibration systems. The real performance of the detector, which always meets,
and sometimes exceeds, design expectations, is also shown. Some important
aspects of the Borexino project, i.e. the fluid handling plants, the
purification techniques and the filling procedures, are not covered in this
paper and are, or will be, published elsewhere (see Introduction and
Bibliography).Comment: 37 pages, 43 figures, to be submitted to NI
New limits on nucleon decays into invisible channels with the BOREXINO Counting Test Facility
The results of background measurements with the second version of the
BOREXINO Counting Test Facility (CTF-II), installed in the Gran Sasso
Underground Laboratory, were used to obtain limits on the instability of
nucleons, bounded in nuclei, for decays into invisible channels ():
disappearance, decays to neutrinos, etc. The approach consisted of a search for
decays of unstable nuclides resulting from and decays of parents
C, C and O nuclei in the liquid scintillator and the water
shield of the CTF. Due to the extremely low background and the large mass (4.2
ton) of the CTF detector, the most stringent (or competitive) up-to-date
experimental bounds have been established: y, y, y and y, all at 90% C.L.Comment: 22 pages, 3 figures,submitted to Phys.Lett.
Science and technology of BOREXINO: A Real time detector for low-energy solar neutrinos: A Real Time Detector for Low Energy Solar Neutrinos
BOREXINO, a real-time device for low energy neutrino spectroscopy is nearing completion of construction in the underground laboratories at Gran Sasso, Italy (LNGS). The experiment's goal is the direct measurement of the flux of 7Be solar neutrinos of all flavors via neutrino-electron scattering in an ultra-pure scintillation liquid. Seeded by a series of innovations which were brought to fruition by large scale operation of a 4-ton test detector at LNGS, a new technology has been developed for BOREXINO. It enables sub-MeV solar neutrino spectroscopy for the first time. This paper describes the design of BOREXINO, the various facilities essential to its operation, its spectroscopic and background suppression capabilities and a prognosis of the impact of its results towards resolving the solar neutrino problem. BOREXINO will also address several other frontier questions in particle physics, astrophysics and geophysics
Measurements of extremely low radioactivity levels in BOREXINO
The techniques researched, developed and applied towards the measurement of
radioisotope concentrations at ultra-low levels in the real-time solar neutrino
experiment BOREXINO at Gran Sasso are presented and illustrated with specific
results of widespread interest. We report the use of low-level germanium gamma
spectrometry, low-level miniaturized gas proportional counters and low
background scintillation detectors developed in solar neutrino research. Each
now sets records in its field. We additionally describe our techniques of
radiochemical ultra-pure, few atom manipulations and extractions. Forefront
measurements also result from the powerful combination of neutron activation
and low-level counting. Finally, with our techniques and commercially available
mass spectrometry and atomic absorption spectroscopy, new low-level detection
limits for isotopes of interest are obtained.Comment: 27 pages, 5 figures. Submitted to Astroparticle Physics (17 Sep
2001). Spokesperson of the Borexino Collaboration: G. Bellini. Corresponding
author: W. Hampe
Study of neutrino electromagnetic properties with the prototype of the Borexino detector
Abstract The results of background measurements with the prototype of the Borexino detector (CTF) have been used to obtain an upper bound on the neutrino magnetic moment, µ ν . The new upper limit for µ ν from pp and 7 Be solar neutrinos is (5.5 × 10 −10 )µ B (90% c.l.) in the Standard Solar Model scenario. This is the first limit on µ ν obtained using sub-MeV neutrinos. The sensitivity of the prototype to the neutrino charge radius and the neutrino radiative decay are also presented
Genetic differentiation of Artemia franciscana (Kellogg, 1906) in Kenyan coastal saltworks
The nature of genetic divergence between the Artemia population native to San Francisco Bay, (SFB) USA and those from the introductions of SFB material in the Kenyan coast two decades ago were investigated using the mitochondrial DNA (mtDNA) and heat shock protein 70 (Hsp70) gene molecular markers. The DNA was extracted from 80 single Artemia cysts using the Chelex protocol. The 1,500 bp fragment of the 12S - 16S region of the mtDNA and a 1,935 bp fragment of the Hsp70 gene were amplified through Polymerase Chain Reaction (PCR) followed by Restriction Fragment Length Polymorphism (RFLP) digestion using appropriate endonucleases. The mtDNA analysis indicated higher haplotype diversity (0.76 ± 0.07) in Artemia from Fundisha saltworks while the rest of the samples were monomorphic. A private haplotype (AAABBA) in Fundisha samples confirmed a molecular evidence of a systematic genetic differentiation albeit in an insignificant manner (P > 0.05). There was molecular evidence of coexistence of SFB and GSL Artemia strains in Fundisha saltworks. The monomorphic DNA fingerprint in Kensalt Artemia cysts was probably caused by non-sequential Artemia culture system and limited mtDNA fragment size analysed. The Hsp70 gene RFLP fingerprint did not show any unique gene signatures in the Kenyan Artemia samples suggesting that other factors other than Hsp70 were involved in their superior thermotolerance. Further genetical studies based on the larger mtDNA fragment using robust genetic markers are recommended. Ecological studies of the heat shock protein family and the stress response would be more relevant than the qualitative RFLP technique
A continuous pleated birod for converting contractions into twisting through instability
The mechanical behavior of a structure made by joining two flexible flanges with a deformable pleated web, simply called continuous birod, is investigated. When axially loaded, the continuous birod shows an unconventional buckling phenomenon that couples axial contractions and helical twist, with a softening-hardening postcritical force–displacement response. In this work we propose an analytical model capable to predict the critical load and displacement of a continuous birod under axial compression. Our model does not contain any heuristic term: all the parameters have a clear physical-geometrical interpretation and can be easily identified. The obtained closed-form expressions for the critical load and displacement are in good agreement with experimental evidences and finite element simulations. The model can be exploited for the design of compliance and multistable devices for advanced applications
Linear Models of a Stiffened Plate via Gamma-Convergence
We consider a family of three-dimensional stiffened plates whose dimensions are scaled through different powers of a small parameter epsilon. The plate and the stiffener are assumed to be linearly elastic, isotropic, and homogeneous. By means of Gamma-convergence, we study the asymptotic behavior of the three-dimensional problems as the parameter e tends to zero. For different relative values of the powers of the parameter epsilon, we show how the interplay between the plate and the stiffener affects the limit energy. We derive twenty-three limit problems
Simultaneous measurement of gamma rays and radon emission (SIMGRAE) for solid samples radioactivity assessment
A gamma/radon high-sensitivity radioactivity counter has been built in the frame of a research and development aimed at assessing the effect of construction materials on the annual radioactive dose absorbed by individuals. The counter features simultaneous gamma measurement (by high-resolution germanium spectroscopy) and radon evaluation through electrostatic collection and alpha spectroscopy of radon daughters
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