http://hdl.handle.net/2122/171 Sat, 18 May 2013 08:08:56 GMT 2013-05-18T08:08:56Z http://hdl.handle.net/2122/6116 Title: GEMS: Underwater spectrometer for long-term radioactivity measurements Authors: L.Sartini; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: GEMS (Gamma Energy Marine Spectrometer) is a prototype of an autonomous radioactivity sensor for underwater measurements, developed in the framework of the KM3NeT Design Study (DS) EC project. The spectrometer is sensitive to gamma rays produced by 40K decays and it is also able to detect other natural (e.g., 238U, 232Th) and anthropogenic radionuclides (e.g. 137Cs). The decay of 40K, contained in sea salt, particulate and sediments, is one of the main sources of photon background in the underwater environment. GEMS was first calibrated in the laboratory using known sources, also in order to evaluate the performance of the instrument. In November 2008 GEMS was deployed at a depth of 3200 m in the area of Capo Passero (in the Ionian Sea) to acquire data autonomously. After recovery of the spectrometer six months later (May 2009) it was found that the instrument had worked within the specifications and acquired data over the full deployment period. These data allowed us to investigate over a long period the possible variations of activity at the Capo Passero site. GEMS is suitable to be used either in autonomous mode or as payload of seafloor observatories or vehicles. Mon, 03 May 2010 22:00:00 GMT http://hdl.handle.net/2122/6116 2010-05-03T22:00:00Z http://hdl.handle.net/2122/1461 Title: The ocean wave dynamo: a source of magnetic field fluctuations Authors: Watermann, J.; NATO SACLANT Undersea Research Centre, La Spezia, Italy; Magunia, A.; Institut für Meteorologie und Geophysik, J.-W.-Goethe-Universitat, Frankfurt/Main, Germany; Gambetta, M.; Dipartimento di Scienze della Terra, Universitá di Genova, Italy; Bozzo, E.; Dipartimento di Scienze della Terra, Universitá di Genova, Italy Abstract: The alternating magnetic dynamo field of sea surface waves, a consequence of their Lorentz electric field, has been observed with a pair of simultaneously operated, closely spaced tri-axial magnetometers. Measurements from a magnetometer located in the centre of a tiny, uninhabited island served to compensate measurements from a near-shore magnetometer for magnetic pulsations of ionospheric origin, leaving the ocean wave dynamo field, effective close to shore only, as the dominant residual magnetic field. Amplitude and frequency of waves and swell were recorded with a vertical accelerometer (wave rider buoy) floating nearby on the sea surface. A spectral analysis was performed on ten nighttime intervals of three hours length each, and for every interval, the peak power of the surface waves (obtained from the wave rider) was compared with the peak power of the residual horizontal magnetic field (after the background field had been removed). The results suggest that the dual-sensor magnetic field observations yield, within the limits of statistical significance, a good quantitative description of the amplitude and frequency of sea surface waves and swell. Fri, 31 Jul 1998 22:00:00 GMT http://hdl.handle.net/2122/1461 1998-07-31T22:00:00Z