A new generation photodetector for astroparticle physics: the VSiPMT

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

Why the distribution matters: using discrete event simulation to demonstrate the impact of the distribution of procedure times on hospital operating room utilisation and average procedure cost

Background: Economic evaluations include estimates of surgical procedures costs that have usually been derived by allocating operating room (OR) costs in proportion to the average duration of different procedure types. However, ORs run with average utilisation below 100%, due to idle time between procedures and at the end of the day. Longer and less predictable procedures generate greater OR idle time, for a given tolerance of schedule over-runs. Estimates of surgical procedure costs that are based on average procedure duration alone as a measure of OR resource consumption will not capture the impact of the length and variability of procedure duration on OR idle time and capacity utilisation. Objective: To demonstrate how real-world OR scheduling practices lead to different levels of resource consumption than predicted by simple micro-costing approaches based on average procedure duration, and how those differences can vary between procedures with significantly different distributions of duration. Methods: We use a discrete event simulation model, calibrated with real-world data from a single surgical centre in Belgium, to compare simulated resource consumption, including idle time, for two alternative surgical procedures for ablation for atrial fibrillation. Results: We demonstrate that simple micro-costing approaches can under-estimate effective resource consumption between 31% and 48% for a procedure with long and unpredictable duration. For a shorter and more predictable procedure the under-estimate is only 15%. Conclusion: Simple approaches to estimating procedure costs may under-estimate resource consumption and do so in a way that is biased against technologies with shorter and more predictable procedure duration. For health technology decisions where a substantial part of costs are OR resources, a more sophisticated approach, taking account of the real-world implications of the distribution of procedure durations, should be used to avoid potential bia

A versatile cryogenic system for liquid argon detectors

Detectors for direct dark matter search using noble gases in liquid phase as detection medium need to be coupled to liquefaction, purification and recirculation systems. A dedicated cryogenic system has been assembled and operated at the INFN-Naples cryogenic laboratory with the aim to liquefy and purify the argon used as active target in liquid argon detectors to study the scintillation and ionization signals detected by large SiPMs arrays. The cryogenic system is mainly composed of a double wall cryostat hosting the detector, a purification stage to reduce the impurities below one part per billion level, a condenser to liquefy the argon, a recirculation gas panel connected to the cryostat equipped with a custom gas pump. The main features of the cryogenic system are reported as well as the performances, long term operations and stability in terms of the most relevant thermodynamic parameters.Comment: Prepared for submission to JINST - LIDINE2022 September 21-23, 2022 - University of Warsaw Librar

The VSiPMT project

Photon detection is a key factor to study many physical processes in several areas of fundamental physics research. Focusing the attention on photodetectors for particle astrophysics, the future experiments aimed at the study of very high-energy or extremely rare phenomena (e.g. dark matter, proton decay, neutrinos from astrophysical sources) will require additional improvements in linearity, gain, quantum efficiency and single photon counting capability. To meet the requirements of this class of experiments, we propose a new design for a modern hybrid photodetector: the VSiPMT (Vacuum Silicon PhotoMultiplier Tube). The idea is to replace the classical dynode chain of a PMT with a SiPM, which therefore acts as an electron detector and amplifier. The aim is to match the large sensitive area of a photocathode with the performances of the SiPM technology. We now present the preliminary study we are performing to realize a 3-inches VSiPMT prototype