120330344
High accuracy measurements of drift time in the streamer mode
Abstract A nitrogen laser focused to a 50 μm spot diameter with a minimum ionising energy deposit was used to scan a streamer tube. Results were obtained for the drift velocity and the spatial resolution. The resolution averaged, σ = ±25 μ m over the total drift length of 8 mm at atmospheric pressure. The charge multiplication region was also observed and could be separated into two regions, a region of low charge multiplication with increased drift velocity and an avalanche region with constant drift time.
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.
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.
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.
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.
121134571
Procedures and results of the measurements on large area photomultipliers for the NEMO project
Abstract The selection of the photomultiplier plays a crucial role in the R&D activity related to a large-scale underwater neutrino telescope. This paper illustrates the main procedures and facilities used to characterize the performances of 72 large area photomultipliers, Hamamatsu model R7081 sel. The voltage to achieve a gain of 5×10 7 , dark count rate and single photoelectron time and charge properties of the overall response were measured with a properly attenuated 410 nm pulsed laser. A dedicated study of the spurious pulses was also performed. The results prove that the photomultipliers comply with the general requirements imposed by the project.
118473267
A parameterisation of the flux and energy spectrum of single and multiple muons in the deep water or ice
Abstract Atmospheric muons play an important role in underwater/ice neutrino detectors. A parameterisation of the flux of single and multiple muon events, of their lateral distribution and energy spectrum is presented. The kinematics parameters were modelled starting from a full Monte Carlo simulation of the interaction of primary cosmic rays with atmospheric nuclei. The parametric formulas are valid for a vertical depth of 1.5–5 km w.e. and up to 85 ∘ for the zenith angle, and can be used as input for a fast simulation of atmospheric muons in underwater/ice detectors.
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.
120966174
The NEMO project: A status report
Abstract The latest results and the activities towards the construction of a km 3 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 NEMO Phase-1 project has validated several technologies proposed for the construction of the km 3 detector on a test site at 2000 m depth. The new infrastructure on the candidate Capo Passero site set up as part of the Phase-2 project will provide the possibility to test detector components at 3500 m depth.
110859812
The Central Logic Board and its auxiliary boards for the optical module of the KM3Net detector
The KM3Net neutrino telescope will be composed of many optical modules, each of them containing 31 (3") photomultipliers, connected to a Central Logic Board. The Central Logic Board integrates Time to Digital Converters that measure Time over Threshold of the photomultipliers signals while White Rabbit is used for the optical modules time synchronization. Auxiliary boards have also been designed and built in order to test and extend the performance of the Central Logic Board. The Central Logic Board, as well as the auxiliary boards, will be presented by focusing on the design consideration, prototyping issues and tests.