Giancarlo Barbarino

Time structure of the extensive air shower front

Abstract The GREX/COVER_PLASTEX experiment has measured the temporal and spatial fine structure of the EAS disc at sea level in a new and original way, using resistive plate counter detectors for direct measurements of the arrival time of each particle crossing the detector. Data were taken at EAS core distances up to 100 m for shower size N > 105 (PeV energy range). Arrival times of shower particles were measured with nanosecond accuracy. More than 450000 air shower events have been included in this analysis.

Use of RPC in EAS physics with the COVER_PLASTEX experiment

Abstract Bakelite Resistive Plate Counters (RPCs) have been used for the first time in Extensive Air Shower (EAS) physics with the COVER_PLASTEX experiment in Haverah Park, near Leeds, UK for a detailed investigation of the space-time structure of the shower front. For this purpose a new front-end electronics has been developed and an accurate investigation on the RPC performances and pick-up characteristics has been performed. Measurements of the noise, cross talk, after-pulses and detector saturation have permitted to understand the behaviour of this detector in operational conditions. A direct comparison with scintillators of the GREX array demonstrates the capability of the RPC to measure the lateral distribution of shower particles and emphasizes the advantage of this detector for a detailed analysis of EAS front characteristics.

Silicon Photo Multipliers Detectors Operating in Geiger Regime: an Unlimited Device for Future Applications

Photon detectors are indispensable in many areas of fundamental physics research, particularly in the emerging fields of particle astrophysics, nuclear and particle physics, as well as in medical equipment (i.e. PET), in physical check-ups and diagnosis as in-vitro inspection (Radioimmunoassay and Enzyme immunoassay as luminescent, fluorescent, Chemiluminescent Immunoassay), biomedicine, industrial application, in environmental measurement equipment (like dust counters used to detect dust contained in air or liquids, and radiation survey monitors used in nuclear power plants). In astroparticle physics, photons detectors play a crucial role in the detection of fundamental physical processes: in particular, most of the future experiments which aimed at the study of very high-energy (GRB, AGN, SNR) or extremely rare phenomena (dark matter, proton decay, zero neutrinosdouble beta decay, neutrinos from astrophysical sources)[3-7] are based on photons detection. The needs of very high sensitivity push the designing of detectors whose sizes should greatly exceed the dimensions of the largest current installations. In the construction of such large-scale detectors no other option remains as using natural media atmosphere, deep packs of ice, water and liquefied gases at cryogenic temperatures [8-13]. In these (transparent) media, charged particles, originating from interaction or decays of primary particles, emit Cherenkov radiation or fluorescence light, detected by photosensitive devices. Hence, for the improvement in the quality of the experimental results a particular attention should be paid to the improvement of photon detectors performances. In underwater neutrino telescopes (but this is applicable also to other experiments) Cherenkov light, emitted by charged leptons stemming from neutrino interaction, hits photomultipliers (PMT) situated at different distances from the track. This implies, that the response of PMTs should be linear in a very wide range from high illumination to the single photon. Another area of interest is the direct searches of Dark Matter in form of WIMPs: in these experiments it is exploited the scintillation properties of double-phase (liquid-gas) detectors, where primary and secondary scintillation light signals are detected by high-efficiency PMTs, immersed in cryogenic liquids or low temperature gases (89 K for the liquid argon) [14-17]. The next generation of experiments requires further improvement in linearity, gain, and sensitivity (quantum efficiency and single photon counting capability) of PMTs.

Preliminary results on dielectric mirror damage due to the radiation of a high K undulator

Abstract Due to the high K value (4.8) of the LELA undulator, we expect a significant UV induced damage of TiO2ue5f8SiO2 dielectric mirrors. Preliminary tests on commercial grade mirrors exhibit a great loss of reflectivity, due to two distinct processes of induced degradation. One of them is surface absorption of carbon in the upper SiO2-air interface. It is not affected by annealing. The other corresponds to a volume damage induced by the high energy radiation present during injection into the accelerator or during the runs at 1.5 GeV for synchrotron radiation production.

A new generation photodetector for astroparticle physics: the VSiPMT

Abstract The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design we proposed for a revolutionary photon detector. The main idea is to replace the classical dynode chain of a PMT with a SiPM (G-APD), the latter acting as an electron detector and amplifier. The aim is to match the large sensitive area of a photocathode with the performance of the SiPM technology. The VSiPMT has many attractive features. In particular, a low power consumption and an excellent photon counting capability. To prove the feasibility of the idea we first tested the performance of a special non-windowed SiPM by Hamamatsu (MPPC) as electron detector and current amplifier. Thanks to this result Hamamatsu realized two VSiPMT industrial prototypes. In this work, we present the results of a full characterization of the VSiPMT prototype.

GREX/COVER_PLASTEX: an experiment to analyze the space-time structure of extensive air showers produced by primary cosmic rays of 1015 eV

Abstract A novel experimental installation is described in which the traditional method of detecting extensive air showers with scintillation counters is significantly extended by the addition of limited streamer tube hodoscopes (LST) and layers of resistive plate counters (RPC). Runs with the scintillator array, GREX, at Haverah Park have demonstrated the power of the LST hodoscopes to determine the direction of arrival of muons, electrons and photons in air showers while the RPC system permits the relative arrival time of individual particles and the temporal thickness and structure of the shower disc to be obtained. The potential of these technical advances for studying the longitudinal profile of air showers produced by primaries of about 1000 TeV is briefly discussed. First measurements of thickness and time profile of EAS front are also reported.

Proof of feasibility of the Vacuum Silicon PhotoMultiplier Tube (VSiPMT)

The Vacuum Silicon PhotoMultiplier Tube (VSiPMT) is an innovative design we propose for a modern hybrid photodetector based on the combination of a Silicon PhotoMultiplier (SiPM) with a hemispherical vacuum glass PMT standard envelope. The basic idea is to replace the classical dynode chain of a PMT with a SiPM, which acts as an electron multiplying detector. Such a solution will match the goal of a large photocathode sensitive area with the performances of a SiPM. This will lead to many advantages such as lower power consumption, mild sensitivity to magnetic fields and high quantum efficiency. The feasibility of this idea has been throughly studied both from a theoretical and experimental point of view. As a first step we performed the full characterization of a special non-windowed Hamamatsu MPPC with a laser source. The response of the SiPM to an electron beam was studied as a function of the energy and of the incident angle by means of a Geant4-based simulation. In this paper we present the preliminary results of the characterization of the SiPM with an electron source and we discuss how the development of next generation SiPMs will overcome the main weaknesses of VSiPMT, such as relatively low PDE and high photocathode voltage.

The QTP system for the MACRO experiment at Gran Sasso

Abstract We describe a system to measure charge and time of the streamer tube signals developed, in collaboration with CAEN company, for the MACRO experiment. Intensive test on prototype and final production have been performed. Preliminary results are reported

NORA based TDC in 90 nm CMOS

Abstract This paper investigates the idea to construct Time-to-Digital Converter (TDC) circuits based on dynamic precharged NORA delay elements. A self-charging technique is proposed in order to accommodate the dynamic delay elements in a ring-oscillator like structure. The employ of dynamic logic allows to reduce the TDC resolution with respect to previous TDCs based on standard CMOS logic. The ring-oscillator like topology imparts a very large dynamic range to the proposed circuit. In the paper a TDC, based on a Pseudo-differential topology, is presented, that is robust against PVT and mismatch variations. The TDC is fabricated in 90xa0nm CMOS technology, and presents a resolution of 25xa0ps. Experimental measurements confirm the effectiveness of the idea and show that the proposed TDCs exhibit low INL and a large dynamic-range when compared with state-of-the art circuits.

The vacuum silicon photomultiplier tube (VSiPMT): A new concept of photon detector. first feasibility results

The future astroparticle experiments will study both energetic phenomena and extremely rare events from astro-physical sources. Since most of these families of experiments are carried out by using scintillation phenomena, Cherenkov or fluorescence radiation, the development of photosensitive detectors seems to be the right way to increase the experimental sensitivity. We therefore propose an innovative design for a modern, high gain, silicon-based Vacuum Silicon Photomultiplier Tube (VSiPMT), which combines three fully established and well-understood technologies: the manufacture of hemispherical vacuum tubes with the possibility of very large active areas, the photocathode glass deposition and the recent Geiger-mode avalanche silicon photodiode (G-APD) for which a mass production is today available. This new design, based on G-APD as the electron multiplier, allows overcoming the limits of the classical PMT dynode chain. In this work VSiPMT first feasibility results will be presented.