C.M. Mollo

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.

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.

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.

A new instrument for high statistics measurement of photomultiplier characteristics

Since the early days of experimental particle physics photomultipliers (PMTs) have played an important role in the detector design. Thanks to their capability of fast photon counting, PMTs are extensively used in the new-generation of astroparticle physics experiments, such as air, ice and water Cherenkov detectors. Small size PMTs (

First results of performance tests of the newly designed Vacuum Silicon Photo Multiplier Tube (VSiPMT).

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The trigger and data acquisition for the NEMO-Phase 2 tower

3 inches diameter) show little sensitivity to the Earth magnetic field, small transit time, stable transit time spread; the price per photocathode area is less comparing to the one for the large area PMTs, typically used so far in such applications. Together with developments and reduced price of multichannel electronics, the use of PMTs of 3-inches or smaller diameter is a promising option even for nowadays large volume detectors. In this paper we report on the design and performance of a new instrument for mass characterisation of PMTs (from 1 inch to 3 inches size), capable to calibrate hundreds of PMTs per day and provide measurements of dark counts, signal amplitude, late-, delayed-, pre- and after-pulses, transit time and transit time spread.

Long-term optical background measurements in the Capo Passero deep-sea site

We invented (2007) the VSiPMT, a novel, high-gain, photo detector device and we publically proposed this idea in an International Conference for the first time at the 11th Topical Seminar on Innovative Particle and Radiation Detectors (IPRD08) in Siena, triggering deep discussions on the feasibility of the device itself and on the convenience of such a solution. After several years spent in designing, evaluation, tests and eventually negotiations with some suppliers, we finally got a couple of prototypes of the Vacuum Silicon Photo Multiplier Tube (VSiPMT) made under our specifications by Hamamatsu. We present in this paper the most important results of characterization tests of the first prototypes of the VSiPMT.

VSiPMT: An hybrid approach to high resolution photodetectors

In the framework of the Phase 2 of the NEMO neutrino telescope project, a tower with 32 optical modules is being operated since march 2013. A new scalable Trigger and Data Acquisition System (TriDAS) has been developed and extensively tested with the data from this tower. Adopting the all-data-to-shore concept, the NEMO TriDAS is optimized to deal with a continuous data-stream from off-shore to on-shore with a large bandwidth. The TriDAS consists of four computing layers: (i) data aggregation of isochronal hits from all optical modules; (ii) data filtering by means of concurrent trigger algorithms; (iii) composition of the filtered events into post-trigger files; (iv) persistent data storage. The TriDAS implementation is reported together with a review of dedicated on-line monitoring tools.

VSiPMT for underwater neutrino telescopes

In March 2013, the Nemo Phase-2 tower has been successfully installed at 100 km off-shore Capo Passero (Italy) and 3500 m depth. This 8-floor tower hosts 32 10-inch PMTs. Results from optical background measurements are presented. In particular, the analyzed rates show stable and low baseline values, compatible with the contribution of 40K light emission, with a small percentage of light bursts due to bioluminescence. All these features are a confirmation of the stability and good optical nature of the site.

R&D of a pioneering system for a high resolution photodetector: The VSiPMT

The VSiPMT (Vacuum Silicon Photomultiplier Tube) is an innovative design for a revolutionary hybrid photodetector. The idea consists in replacing the classic dynode chain of a classic PMT with a SiPM. This new device aims at extending SiPM technology to large detection volumes. In this configuration, we match the large sensitive area of a photocathode with the performance of SiPM technology, which thererefore acts like an electron detector and current amplifier. The excellent photon counting capability, fast response, low power consumption and great stability are among the most attractive features of the VSiPMT. Hamamatsu realized two VSiPMT industrial prototypes with a photocathode of 3 mm diameter. In this work we present the progresses on the realization of a 1-inch prototype based on CsI photocathode and the preliminary tests we are performing on it.