LHCb RICH Upgrade: an overview of the photon detector and electronics system

The LHCb experiment is one of the four large detectors operating at the LHC at CERN and it is mainly devoted to CP violation measurements and to the search for new physics in rare decays of beauty and charm hadrons. The data from the two Ring Image Cherenkov (RICH-1 and RICH-2) detectors are essential to identify particles in a wide momentum range. From 2019 onwards 14 TeV collisions with luminosities reaching up to $2\cdot10^{33}$ cm$^{-2}$ s$^{-1}$ with 25 ns bunch spacing are planned, with the goal of collecting 5 fb$^{-1}$ of data per year. In order to avoid degradation of the PID performance at such high rate (40 MHz), the RICH detector has to be upgraded. New photodetectors (Multi-anode photomultiplier tubes, MaPMTs) have been chosen and will be read out using a 8-channels chip, named CLARO, designed to sustain a photon counting rate up to 40 MHz, while minimizing the power consumption and the cross-talk. A 128-bit digital register allows selection of thresholds and attenuation values and provides features useful for testing and debugging. Photosensors and electronics are arranged in basic units, the first prototypes of which have been tested in charged particle beams in autumn 2014. An overview of the CLARO features and of the readout electronics is presented

Photodetectors and front-end electronics for the LHCb RICH upgrade

The RICH detectors of the LHCb experiment provide identification of hadrons produced in high energy proton-proton collisions in the LHC at CERN over a wide momentum range (2 to 100 GeV/c). Cherenkov light is collected on photon detector planes sensitive to single photons. The RICH will be upgraded (in 2019) to read out every bunch crossing, at a rate of 40 MHz. The current hybrid photon detectors (HPD) will be replaced with multi-anode photomultiplier tubes (customisations of the Hamamatsu R11265 and the H12699 MaPMTs). These 8$\times$8 pixel devices meet the experimental requirements thanks to their small pixel size, high gain, negligible dark count rate ($\sim$50 Hz/cm$^2$) and moderate cross-talk. The measured performance of several tubes is reported, together with their long-term stability. A new 8-channel front-end chip, named CLARO, has been designed in 0.35 $\mu$m CMOS AMS technology for the MaPMT readout. The CLARO chip operates in binary mode and combines low power consumption (\hbox{$\sim$1 mW/Ch}), wide bandwidth (baseline restored in $\leq$25 ns) and radiation hardness. A 12-bit digital register permits the optimisation of the dynamic range and the threshold level for each channel and provides tools for the on-site calibration. The design choices and the characterization of the electronics are presented

Characterization of the Hamamatsu R11265-103-M64 multi-anode photomultiplier tube

The aim of this paper is to fully characterize the new multi-anode photomultiplier tube R11265-103-M64, produced by Hamamatsu. Its high effective active area (77%), its pixel size, the low dark signal rate and the capability to detect single photon signals make this tube suitable for an application in high energy physics, such as for RICH detectors. Four tubes and two different bias voltage dividers have been tested. The results of a standard characterization of the gain and the anode uniformity, the dark signal rate, the cross-talk and the device behaviour as a function of temperature have been studied. The behaviour of the tube is studied in a longitudinal magnetic field up to 100 Gauss. Shields made of a high permeability material are also investigated. The deterioration of the device performance due to long time operation at intense light exposure is studied. A quantitative analysis of the variation of the gain and the dark signals rate due to the aging is described.Comment: 22 page

Large area Si low-temperature light detectors with Neganov-Luke effect

Next generation calorimetric experiments for the search of rare events rely on the detection of tiny amounts of light (of the order of 20 optical photons) to discriminate and reduce background sources and improve sensitivity. Calorimetric detectors are the simplest solution for photon detection at cryogenic (mK) temperatures. The development of silicon based light detectors with enhanced performance thanks to the use of the Neganov-Luke effect is described. The aim of this research line is the production of high performance detectors with industrial-grade reproducibility and reliability.Comment: 4 pages, 2 figure

Transformer coupling and its modelling for the flux-ramp modulation of rf-SQUIDs

Microwave frequency domain multiplexing is a suitable technique to read out a large number of detector channels using only a few connecting lines. In the HOLMES experiment this is based on inductively coupled rf-SQUIDs (Superconducting QUantum Interference Devices) fed by TES (Transition Edge Sensors). Biasing of the whole rf-SQUID chain is provided with a single transmission line by means of the recently introduced flux-ramp modulation technique, a sawtooth signal which allows signal reconstruction while operating the rf-SQUIDs in open loop condition. Due to the crucial role of the sawtooth signal, it is very important that it does not suffer from ground loop disturbances and EMI. Introducing a transformer between the biasing source and the SQUIDs is very effective in suppressing disturbances. The sawtooth signal has slow and fast components, and the period can vary between a few kHz up to MHz depending on the TES signal and SQUID characteristics. A transformer able to face such a broad range of conditions must have very stringent characteristics and needs to be custom designed. Our solution exploits standard commercial, and inexpensive, transformers for LAN networks used in a suitable combination. A model that allows to take care of the low as well as of the high frequency operating range has been developed

Optic pathway glioma in type 1 neurofibromatosis: Review of its pathogenesis, diagnostic assessment, and treatment recommendations

Type 1 neurofibromatosis (NF1) is a dominantly inherited condition predisposing to tumor development. Optic pathway glioma (OPG) is the most frequent central nervous system tumor in children with NF1, affecting approximately 15-20% of patients. The lack of well-established prognostic markers and the wide clinical variability with respect to tumor progression and visual outcome make the clinical management of these tumors challenging, with significant differences among distinct centers. We reviewed published articles on OPG diagnostic protocol, follow-up and treatment in NF1. Cohorts of NF1 children with OPG reported in the literature and patients prospectively collected in our center were analyzed with regard to clinical data, tumor anatomical site, diagnostic workflow, treatment and outcome. In addition, we discussed the recent findings on the pathophysiology of OPG development in NF1. This review provides a comprehensive overview about the clinical management of NF1-associated OPG, focusing on the most recent advances from preclinical studies with genetically engineered models and the ongoing clinical trials