Optical background measurement in a potential site for the NEMO KM undersea neutrino telescope

We describe the measurement of the deep sea optical background in some sites south of Capo Passero, Sicily. A continuous flux of about 440 photons cm -2 s -1 in the wavelength interval 440-550 nm is estimated due to the decays of the 40K contained in the sea water. Bioluminescence light bursts are also observed and an example of time evolution is reported. All the measurements were accomplished using a deep sea module also described in this article

Gear transmission dynamic: Effects of tooth profile deviations and support flexibility

In this work a non-linear dynamic model of spur gear transmissions previously developed by the authors is extended to include both desired (relief) and undesired (manufacture errors) deviations in the tooth profile. The model uses a hybrid method for the calculation of meshing forces, which combines FE analysis and analytical formulation, so that it enables a very straightforward implementation of the tooth profile deviations. The model approach handles well non-linearity due to the variable meshing stiffness and the clearances involved in gear dynamics, also including the same phenomena linked to bearings. In order to assess the ability of the model to simulate the impact of the deviations on the transmission dynamics, an example is presented including profile deviations under different values of transmitted torque. Several results of this example implementation are presented, showing the model's effectiveness.This paper has been developed in the framework of Project DPI2006-14348 funded by the Spanish Ministry of Science and Technology

Measurement of the atmospheric muon flux with the NEMO Phase-1 detector

The NEMO Collaboration installed and operated an underwater detector including prototypes of the critical elements of a possible underwater km3 neutrino telescope: a four-floor tower (called Mini-Tower) and a Junction Box. The detector was developed to test some of the main systems of the km3 detector, including the data transmission, the power distribution, the timing calibration and the acoustic positioning systems as well as to verify the capabilities of a single tridimensional detection structure to reconstruct muon tracks. We present results of the analysis of the data collected with the NEMO Mini-Tower. The position of photomultiplier tubes (PMTs) is determined through the acoustic position system. Signals detected with PMTs are used to reconstruct the tracks of atmospheric muons. The angular distribution of atmospheric muons was measured and results compared with Monte Carlo simulations.Comment: Astrop. Phys., accepte

Status of NEMO

The activities towards the realization of a km3 Cherenkov neutrino detector carried out by the NEMO Collaboration are described. Long-term exploration of a 3500 m deep-sea site close to the Sicilian coast has shown that it is optimal for the installation of the detector. The realization of a Phase-1 project, which is under way, will validate the proposed technologies for the realization of the km3 detector on a Test Site at 2000 m depth. The realization of a new infrastructure on the candidate site (Phase-2 project) will provide the possibility to test detector components at 3500 m depth

Sensitivity of an underwater Cerenkov km3 telescope to TeV neutrinos from Galactic Microquasars

In this paper are presented the results of Monte Carlo simulations on the capability of the proposed NEMO-km$^3$ telescope to detect TeV muon neutrinos from Galactic microquasars. For each known microquasar we compute the number of detectable events, together with the atmospheric neutrino and muon background events. We also discuss the detector sensitivity to neutrino fluxes expected from known microquasars, optimizing the event selection also to reject the background; the number of events surviving the event selection are given. The best candidates are the steady microquasars SS433 and GX339-4 for which we estimate a sensitivity of about $5\cdot10^{-11}$ erg/cm$^2$ s; the predicted fluxes are expected to be well above this sensitivity. For bursting microquasars the most interesting candidates are Cygnus X-3, GRO J1655-40 and XTE J1118+480: their analyses are more complicated because of the stochastic nature of the bursts.Comment: 20 pages, 3 figures, accepted by Astroparticle Physic

Expansion cone for the 3-inch PMTs of the KM3NeT optical modules

[EN] Detection of high-energy neutrinos from distant astrophysical sources will open a new window on the Universe. The detection principle exploits the measurement of Cherenkov light emitted by charged particles resulting from neutrino interactions in the matter containing the telescope. A novel multi-PMT digital optical module (DOM) was developed to contain 31 3-inch photomultiplier tubes (PMTs). In order to maximize the detector sensitivity, each PMT will be surrounded by an expansion cone which collects photons that would otherwise miss the photocathode. Results for various angles of incidence with respect to the PMT surface indicate an increase in collection efficiency by 30% on average for angles up to 45 degrees with respect to the perpendicular. Ray-tracing calculations could reproduce the measurements, allowing to estimate an increase in the overall photocathode sensitivity, integrated over all angles of incidence, by 27% (for a single PMT). Prototype DOMs, being built by the KM3NeT consortium, will be equipped with these expansion cones.This work is supported through the EU, FP6 Contract no. 011937, FP7 grant agreement no. 212252, and the Dutch Ministry of Education, Culture and Science.Adrián Martínez, S.; Ageron, M.; Aguilar, JA.; Aharonian, F.; Aiello, S.; Albert, A.; Alexandri, M.... (2013). Expansion cone for the 3-inch PMTs of the KM3NeT optical modules. Journal of Instrumentation. 8(3):1-19. https://doi.org/10.1088/1748-0221/8/03/T03006S1198

Sull'adattamento di sonde per NMR

A method for evaluating the matching of a radiofrequency generator to an inductive load is described which may be usefully in the design of NMR probes. It is also reported a universal chart to be used in evaluating for matching network parameters