120826173
Observation of UV photons with a microdot chamber
Microdot gas chambers have been developed which are suitable for imaging x-rays or minimum ionising particles. The problems encountered in the extension of the operating region to gains of over 10000 are described. Results obtained from single photo electron extraction by a UV source from the aluminium drift cathode are presented at avalanche gains of up to 30000. A solution is proposed, which will allow the imaging of single UV photons with less than 60 microns precision in both x and y directions simultaneously, using a detector integrated on to a quartz substrate.
120683548
Large-area low-pressure microstrip gas chambers for thermal neutron imaging
Abstract Thermal neutron imaging gas detectors using counting gas mixtures with gaseous neutron convertors (e.g. 3 He) suffer from inherent limitations in position and time-of-flight resolutions resulting from the long ranges of the released secondary ions in the counting gas and from parallax errors due to the necessary depth of the detector gas volume of >1 cm. In order to overcome these limitations a novel detector generation is presently being constructed utilizing composite neutron convertor foils ( 157 Gd or 6 Li overcoated with CsI) in combination with arrays of large-area microstrip and microdot gas chambers (MSGCs and MDOTs) which are operated in low-pressure, two-stage amplification mode and delivering unsurpassed gains. In this paper the optimization of MSGCs for low-pressure operation with 157 Gd convertors is discussed. The MSGCs are of technologically advanced, robust design, using 3 mm thick synthetic quartz substrates and two closely spaced electrode planes for true two-dimensional position readout. These metal planes are separated by a ∼3 μm thick SiO 2 /DLC double-layer deposited by means of plasma-enhanced CVD. The same fabrication technology is presently prepared for production of large-area MDOTs. The work shall be conducted in collaboration with nine teams from research institutes and industry.
56301921
High rate behavior and discharge limits in micro-pattern detectors
Abstract We present and discuss a set of systematic measurements, carried out with gaseous proportional micro-pattern detectors, in order to assess their maximum gain when irradiated with high-rate soft X-rays and heavily ionizing alpha particles. The inventory of detectors tested includes: micro-strips, micromegas, micro-dot, gas electron multiplier, CAT (compteur a trous), trench (or groove), micro-CAT (or WELL) detectors, as well as systems with two elements of gaseous amplification in cascade. We confirm the general trend of all single-stage detectors to follow Raether's criterion, i.e. a spontaneous transition from avalanche to streamer, followed by a discharge, when the avalanche size reaches a value of a few 10 7 ; a noticeable exception is the micro-dot counter holding more than 10 8 . In multiple structures, where the gain is shared between two devices in cascade, the maximum overall gain under irradiation is increased by at least one order of magnitude; we speculate this to be a consequence of a voltage dependence of Raether's limit, larger for low operating potentials. Our conclusion is that only multiple devices can guarantee a sufficient margin of reliability for operation in harsh LHC running conditions.
121783594
Strong interaction effects in kaonic atoms
Abstract X-rays produced by kaons stopping in targets of S, Co, Ni, Ag and Cd have been observed. The shifts and widths of the last observed mesic X-ray due to the effects of the strong interaction have been measured. In addition, the relative yield of the sulphur K − n = 4 → 3 transition has been measured.
122398469
Doppler-shifted nuclear gamma rays following stopped K− capture in aluminium
Abstract The Doppler broadened 26 Mg * decay gamma peak hasma peak has been observed in coincidence with stopped kaons in an Al target. The results are compared with predictions based on single-nucleon absorption of the kaon.
120592230
A multiterm Boltzmann analysis of drift velocity, diffusion, gain and magnetic-field effects in argon-methane-water-vapour mixtures
Abstract The effect of adding water vapour to argon-methane mixtures used in TPC-type detectors is investigated using the exact multiterm Boltzmann expansion. The transverse and longitudinal diffusion coefficients and the drift velocity are calculated with an accuracy of ± 3, ± 2 and ± 1% respectively. The calculations are extended into the avalanche region and compared to avalanche gain measurements. The effect of misalignment of the electric and magnetic fields on the drift direction is also investigated.
122993753
Recent results and perspectives of the NEMO project
Abstract The latest results and the activities towards the realization of a km 3 Cherenkov neutrino detector carried out by the NEMO Collaboration are described. The realization of a Phase-1 project has validated all relevant technologies proposed for the realization of the km 3 detector on a test site at 2000 m depth. The realization of a new infrastructure on the candidate Capo Passero site (for Phase-2 project) will provide the possibility to test detector components at 3500 m depth.
54839319
A search for time dependent neutrino emission from microquasars with the ANTARES telescope
Results are presented on a search for neutrino emission from a sample of six microquasars, based on the data collected by the ANTARES neutrino telescope between 2007 and 2010. By means of appropriate time cuts, the neutrino search has been restricted to the periods when the acceleration of relativistic jets was taking place at the microquasars under study. The time cuts have been chosen using the information from the X-ray telescopes RXTE/ASM and Swift/BAT, and, in one case, the gamma-ray telescope Fermi/LAT. No statistically significant excess has been observed, thus upper limits on the neutrino fluences have been derived and compared to the predictions by models. Constraints have been put on the ratio of proton to electron luminosity in the jets.
118568116
Updated limits on diffuse fluxes of cosmic neutrinos with 2008-2011 ANTARES data
The ANTARES neutrino telescope detects the Cherenkov radiation emitted along the path of charged particles produced in neutrino interactions. ANTARES is sensitive to all flavors even though it is optimized for muon neutrinos. Several algorithms estimating the deposited energy in the active volume of the detector have been developed and applied to the reconstruction of the primary neutrino energy - this allows to improve the search for a diffuse flux of astrophysical neutrinos. The search for a diffuse flux of cosmic neutrinos at very high energies (E_\nu > 30 TeV) is updated using 4 years of data with the full detector.
36324839
Searches for clustering in the time integrated skymap of the ANTARES neutrino telescope
This paper reports a search for spatial clustering of the arrival directions of high energy muon neutrinos detected by the ANTARES neutrino telescope. An improved two-point correlation method is used to study the autocorrelation of 3058 neutrino candidate events as well as cross-correlations with other classes of astrophysical objects: sources of high energy gamma rays, massive black holes and nearby galaxies. No significant deviations from the isotropic distribution of arrival directions expected from atmospheric backgrounds are observed.
120573311
Underwater acoustic positioning system for the SMO and KM3NeT - Italia projects
In the underwater neutrino telescopes, the positions of the Cherenkov light sensors and their movements must be known with an accuracy of few tens of centimetres. In this work, the activities of the SMO and KM3NeT-Italia teams for the development of an acoustic positioning system for KM3NeT-Italia project are presented. The KM3NeT-Italia project foresees the construction, within two years, of 8 towers in the view of the several km3-scale neutrino telescope KM3NeT.