We report here on a novel analysis of the complete set of four Stokes parameters that uniquely determine the linear and/or circular polarization of the radio signal for an extensive air shower. The ...observed dependency of the circular polarization on azimuth angle and distance to the shower axis is a clear signature of the interfering contributions from two different radiation mechanisms, a main contribution due to a geomagnetically-induced transverse current and a secondary component due to the build-up of excess charge at the shower front. The data, as measured at LOFAR, agree very well with a calculation from first principles. This opens the possibility to use circular polarization as an investigative tool in the analysis of air shower structure, such as for the determination of atmospheric electric fields.
Neutrino-induced showers in the ANTARES deep-sea telescope Dorosti Hasankiadeh, Q.; Löhner, H.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2013, Letnik:
725
Journal Article
Recenzirano
Reconstruction of neutrino-induced showers, initiated by neutral-current interactions, can extend the sensitivity of the ANTARES detector to all neutrino flavors. A major challenge in reconstructing ...showers is their selection from an overwhelming background of down-going atmospheric muons. We have developed a shower selection strategy in order to select up-going showers with high efficiency and purity. We have tuned the selection strategy on Monte-Carlo simulations containing the proper amount of background and atmospheric neutrino-induced showers. The obtained results indicate an efficiency of 21% with a purity better than 90% for the shower selection. We applied the selection strategy to ANTARES experimental data and observed a satisfactory performance of the discriminating variables.
Performance of photo-sensors for KM3NeT Dorosti Hasankiadeh, Q.; Kavatsyuk, O.; Löhner, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2013, Letnik:
725
Journal Article
Recenzirano
The future deep-sea neutrino telescope of multi cubic-km size, KM3NeT, has been designed for an efficient search for high energy neutrinos originating from galactic and extragalactic sources. The ...detection principle relies on the measurement of Cherenkov light emitted from relativistic charged secondary particles caused by the interaction of neutrinos with matter inside or surrounding the active detection volume. In order to provide a homogeneous photon acceptance and to reduce the environmental background by local coincidences between neighbouring photo sensors, a digital optical module (DOM) containing an array of 31 3-in. diameter photomultiplier tubes (PMTs) has been designed. Optimum performance requires sensitivity to single-photo electrons, high collection efficiency at low dark noise, homogeneous photo-cathode response and excellent timing properties. We have studied the response to single photo electrons of a newly developed 3-in. diameter PMT from ET Enterprises Ltd. A 2D-scanning system with a picosecond laser illuminating various positions on the photo-cathode surface was employed to study the timing and homogeneity of the PMT. Results of these investigations indicate good photo-cathode homogeneity, low dark noise on the sub-kHz level, and an average transit-time spread below 2ns. Simulations indicate a significantly improved signal-to-background ratio in the multi-PMT DOM as compared to a triplet of optical modules each housing a single 10-in. PMT.
Photo-sensors for a Multi-PMT optical module in KM3NeT Kavatsyuk, O.; Dorosti-Hasankiadeh, Q.; Löhner, H.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2011, Letnik:
626
Journal Article
Recenzirano
A deep-sea Neutrino Telescope of at least 1
km
3 size (KM3NeT) is being designed to search for high-energy (1–1000
TeV) neutrinos originating from galactic and extragalactic sources. The detection ...principle exploits the measurement of Cherenkov light emitted by charged particles resulting from neutrino interactions in the matter surrounding the telescope. An optical module containing an array of 31 3-in. diameter photomultiplier tubes is a promising alternative to an optical module containing one 10-in. diameter phototube. The single photo-electron response of 3-in. diameter phototubes (Photonis XP53B20 and ETEL 9822B) has been investigated. Phototube characteristics such as the collection efficiency, transit-time spread and peak-to-valley ratio were determined at various positions across the photocathode surface in a remote-controlled 2D scanning system. Results of these investigations are reported and the perspectives to employ the investigated phototube types in the Multi-PMT optical module of the future KM3NeT detector are discussed.
Multi-PMT optical module for the KM3NeT neutrino telescope Kavatsyuk, O.; Dorosti-Hasankiadeh, Q.; Löhner, H.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2012, Letnik:
695
Journal Article
Recenzirano
The future cubic kilometre scale neutrino telescope KM3NeT will employ a novel type of a Digital Optical Module (DOM), developed during the recent FP6 Design Study. A pressure-resistant glass sphere ...hosts 31 photomultiplier tubes (PMTs) of 3-in. diameter, together with all the electronics for high-voltage generation and signal readout. The optical module forms a complete stand-alone detector that is connected to the outside world via a single optical fibre and two copper conductors providing electrical power. The advantages of using multiple small PMTs in the same DOM are the higher quantum efficiency (>30% expected), smaller transit time spread, better two-photon separation capability and directional sensitivity. Moreover, a longer operating lifetime is expected than for large PMTs due to the accumulation of less charge on the anode. In addition, small PMTs are insensitive to the Earth's magnetic field and do not require μ-metal shielding. In order to maximise the detector sensitivity, each PMT will be surrounded by an expansion cone collecting photons that would normally miss the photocathode. Such an expansion cone consists of an aluminium ring filled with silicone gel. An increase in the overall sensitivity, integrated over all angles of incidence, was estimated to be about 27%. Monte-Carlo simulations have shown that a detector configuration with multi-PMT DOMs requires three times less OMs to achieve the same performance as conventional OMs hosting 10-in. PMTs. Prototype DOMs are currently being built by the KM3NeT consortium.
The prototype detection unit of the KM3NeT detector Adrián-Martínez, S.; Ageron, M.; Anghinolfi, M. ...
The European physical journal. C, Particles and fields,
02/2016, Letnik:
76, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A prototype detection unit of the KM3NeT deep-sea neutrino telescope has been installed at 3500m depth 80 km offshore the Italian coast. KM3NeT in its final configuration will contain several ...hundreds of detection units. Each detection unit is a mechanical structure anchored to the sea floor, held vertical by a submerged buoy and supporting optical modules for the detection of Cherenkov light emitted by charged secondary particles emerging from neutrino interactions. This prototype string implements three optical modules with 31 photomultiplier tubes each. These optical modules were developed by the KM3NeT Collaboration to enhance the detection capability of neutrino interactions. The prototype detection unit was operated since its deployment in May 2014 until its decommissioning in July 2015. Reconstruction of the particle trajectories from the data requires a nanosecond accuracy in the time calibration. A procedure for relative time calibration of the photomultiplier tubes contained in each optical module is described. This procedure is based on the measured coincidences produced in the sea by the
40
K background light and can easily be expanded to a detector with several thousands of optical modules. The time offsets between the different optical modules are obtained using LED nanobeacons mounted inside them. A set of data corresponding to 600 h of livetime was analysed. The results show good agreement with Monte Carlo simulations of the expected optical background and the signal from atmospheric muons. An almost background-free sample of muons was selected by filtering the time correlated signals on all the three optical modules. The zenith angle of the selected muons was reconstructed with a precision of about 3
∘
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The multi-PMT optical module for KM3NeT Löhner, H.; Dorosti-Hasankiadeh, Q.; Heine, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Letnik:
718
Journal Article
Recenzirano
In the future neutrino telescope KM3NeT a novel type of optical module (OM) will be employed to optimize the sensitivity to Cherenkov photons and maximize the environmental background suppression. ...The multi-PMT OM, a pressure-resistant glass sphere containing 31 photomultiplier tubes (PMTs) of 3-in. diameter, has been developed and prototyped including electronics for high-voltage generation, signal digitization and optical signal transmission. Monte-Carlo simulations show that a multi-PMT OM configuration requires three times less OMs to achieve the same performance as conventional OMs hosting 10-in. PMTs.
A flux of neutrons from an astrophysical source in the Galaxy can be detected in the Pierre Auger Observatory as an excess of cosmic-ray air showers arriving from the direction of the source. To ...avoid the statistical penalty for making many trials, classes of objects are tested in combinations as nine "target sets," in addition to the search for a neutron flux from the Galactic center or from the Galactic plane. Within a target set, each candidate source is weighted in proportion to its electromagnetic flux, its exposure to the Auger Observatory, and its flux attenuation factor due to neutron decay. These searches do not find evidence for a neutron flux from any class of candidate sources. Tabulated results give the combined p-value for each class, with and without the weights, and also the flux upper limit for the most significant candidate source within each class. These limits on fluxes of neutrons significantly constrain models of EeV proton emission from non-transient discrete sources in the Galaxy.
We report here on a novel analysis of the complete set of four Stokes parameters that uniquely determine the linear and/or circular polarization of the radio signal for an extensive air shower. The ...observed dependency of the circular polarization on azimuth angle and distance to the shower axis is a clear signature of the interfering contributions from two different radiation mechanisms, a main contribution due to a geomagnetically-induced transverse current and a secondary component due to the build-up of excess charge at the shower front. The data, as measured at LOFAR, agree very well with a calculation from first principles. This opens the possibility to use circular polarization as an investigative tool in the analysis of air shower structure, such as for the determination of atmospheric electric fields.
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