21 research outputs found
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TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution
The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a
satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A
ton-level liquid scintillator detector will be placed at about 30 m from a core
of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be
measured with sub-percent energy resolution, to provide a reference spectrum
for future reactor neutrino experiments, and to provide a benchmark measurement
to test nuclear databases. A spherical acrylic vessel containing 2.8 ton
gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon
Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full
coverage. The photoelectron yield is about 4500 per MeV, an order higher than
any existing large-scale liquid scintillator detectors. The detector operates
at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The
detector will measure about 2000 reactor antineutrinos per day, and is designed
to be well shielded from cosmogenic backgrounds and ambient radioactivities to
have about 10% background-to-signal ratio. The experiment is expected to start
operation in 2022
Multielectron transitions above the krypton K edge.
The structures above the Kr K edge are reported and for the first time interpreted as due to multielectron transitions involving K, M, and N electrons. The cross section of the 1s3d multielectron transition is analyzed and an onset more rapid than the one expected according to the ``shake'' model is observed. This behavior is quite well described by a model proposed by St\"ohr, Jaeger, and Rehr [Phys. Rev. Lett. 51, 821 (1983)] based on the exchange interaction
Minimal spanning tree algorithm for Îł-ray source detection in sparse photon images: cluster parameters and selection strategies
The minimal spanning tree (MST) algorithm is a graph-theoretical cluster-finding method. We previously applied it to Îł-ray bidimensional images, showing that it is quite sensitive in finding faint sources. Possible sources are associated with the regions where the photon arrival directions clusterize. MST selects clusters starting from a particular "tree" connecting all the point of the image and performing a cut based on the angular distance between photons, with a number of events higher than a given threshold. In this paper, we show how a further filtering, based on some parameters linked to the cluster properties, can be applied to reduce spurious detections. We find that the most efficient parameter for this secondary selection is the magnitude M of a cluster, defined as the product of its number of events by its clustering degree. We test the sensitivity of the method by means of simulated and real Fermi-Large Area Telescope (LAT) fields. Our results show that is strongly correlated with other statistical significance parameters, derived from a wavelet based algorithm and maximum likelihood (ML) analysis, and that it can be used as a good estimator of statistical significance of MST detections. We apply the method to a 2-year LAT image at energies higher than 3 GeV, and we show the presence of new clusters, likely associated with BL Lac objects
Noble Metal Small Cluster EXAFS
Many experimental and theoretical works (1) have been and are being performed on the structural properties of small metal clusters in order to investigate possible differences from the corresponding bulk metal structure. Attention is generally devoted to the following points: 1) if there is or not a contraction in the lattice parameter with decreasing cluster size; 2) if there is or not a structural transition from the bulk crystallographic structure to icosahedron which should be for thermodynamical and dense packing considerations the most stable structure for a few atoms system
The Adone wiggler xâray lithography beamline
A soft x-ray beamline, utilizing the radiation produced by the six-pole wiggler of the Adone storage ring, has been realized. The beamline allows the exposure of large area resists by means of a double-mirror scanning system or mechanically moving the wafer. The mechanical, geometrical, and spectral characteristics of the beamline will be described
Gli archivi e la montagna : scritti in onore di Paolo De Gasperis
Con il volume Gli archivi e la montagna. Scritti in onore di Paolo De Gasperis, la collana âDocumentaliaâ del Consiglio Nazionale delle Ricerche intende proporre un itinerario di studio inedito e âapertoâ, con lâobiettivo di realizzare uno strumento utile alla conoscenza e alla divulgazione del patrimonio archivistico e documentario custodito dalle maggiori istituzioni italiane interessate alla montagna, con approfondimenti sui loro progetti di ricerca e sulla cultura della montagna piĂč in generale.
Archivi e documenti prodotti dallâuomo nel suo rapporto con la montagna, vissuta, percorsa e salita con intenti scientifici, culturali, sportivi, esistenziali: fonti utili a indagare con metodo scientifico tali legami e a impostare ulteriori approfondimenti e itinerari di ricerca
Recommended from our members
TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution
The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a
satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A
ton-level liquid scintillator detector will be placed at about 30 m from a core
of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be
measured with sub-percent energy resolution, to provide a reference spectrum
for future reactor neutrino experiments, and to provide a benchmark measurement
to test nuclear databases. A spherical acrylic vessel containing 2.8 ton
gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon
Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full
coverage. The photoelectron yield is about 4500 per MeV, an order higher than
any existing large-scale liquid scintillator detectors. The detector operates
at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The
detector will measure about 2000 reactor antineutrinos per day, and is designed
to be well shielded from cosmogenic backgrounds and ambient radioactivities to
have about 10% background-to-signal ratio. The experiment is expected to start
operation in 2022
Recommended from our members
JUNO Physics and Detector
The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton LS detector
at 700-m underground. An excellent energy resolution and a large fiducial
volume offer exciting opportunities for addressing many important topics in
neutrino and astro-particle physics. With 6 years of data, the neutrino mass
ordering can be determined at 3-4 sigma and three oscillation parameters can be
measured to a precision of 0.6% or better by detecting reactor antineutrinos.
With 10 years of data, DSNB could be observed at 3-sigma; a lower limit of the
proton lifetime of 8.34e33 years (90% C.L.) can be set by searching for
p->nu_bar K^+; detection of solar neutrinos would shed new light on the solar
metallicity problem and examine the vacuum-matter transition region. A
core-collapse supernova at 10 kpc would lead to ~5000 IBD and ~2000 (300)
all-flavor neutrino-proton (electron) scattering events. Geo-neutrinos can be
detected with a rate of ~400 events/year. We also summarize the final design of
the JUNO detector and the key R&D achievements. All 20-inch PMTs have been
tested. The average photon detection efficiency is 28.9% for the 15,000 MCP
PMTs and 28.1% for the 5,000 dynode PMTs, higher than the JUNO requirement of
27%. Together with the >20 m attenuation length of LS, we expect a yield of
1345 p.e. per MeV and an effective energy resolution of 3.02%/\sqrt{E (MeV)}$
in simulations. The underwater electronics is designed to have a loss rate
<0.5% in 6 years. With degassing membranes and a micro-bubble system, the radon
concentration in the 35-kton water pool could be lowered to <10 mBq/m^3.
Acrylic panels of radiopurity <0.5 ppt U/Th are produced. The 20-kton LS will
be purified onsite. Singles in the fiducial volume can be controlled to ~10 Hz.
The JUNO experiment also features a double calorimeter system with 25,600
3-inch PMTs, a LS testing facility OSIRIS, and a near detector TAO