S. Blin

MAROC, a generic photomultiplier readout chip

The MAROC ASICs family is dedicated to the readout of 64-channel Multi Anode PMT and similar detectors. Its main roles are to correct the gain spread of MAPMT channels thanks to an individual variable gain preamplifier and to discriminate the input signals (from 50fC i.e 1/3 photo-electron) in order to produce 64 trigger outputs. A multiplexed analog charge output is also available with a dynamic range around 10 pe (∼1.6 pC) and a 12 bit Wilkinson ADC is embedded. Three versions of this chip have been submitted. MAROC 2 is the production version for the ATLAS luminometer and MAROC3 is a version with lower dissipation and significant improvements concerning the charge (30 pe: ∼5 pC) and trigger (discrimination from 10fC). This third version showed very good characteristics that are presented here.

MAROC : Multi-Anode readout chip

MAROC is the readout chip designed for the ATLAS luminometer made of Roman pots. It is used to readout 64 channels multi-anode photomultipliers and supplies 64 trigger outputs and a multiplexed charge output. The second version of this ASIC was received during summer 2006. It has been thoroughly tested at LAL since. This paper presents the results obtained and shows that the performances were found in agreement with the main requirements.

Hadron beam test of a scintillating fibre tracker system for elastic scattering and luminosity measurement in ATLAS

A scintillating fibre tracker is proposed to measure elastic proton scattering at very small angles in the ATLAS experiment at CERN. The tracker will be located in so-called Roman Pot units at a distance of 240 m on each side of the ATLAS interaction point. An initial validation of the design choices was achieved in a beam test at DESY in a relatively low energy electron beam and using slow off-the-shelf electronics. Here we report on the results from a second beam test experiment carried out at CERN, where new detector prototypes were tested in a high energy hadron beam, using the first version of the custom designed front-end electronics. With a spatial resolution of 25 mu m an adequate tracking performance was obtained, under conditions which are similar to the situation at the LHC. In addition, the alignment method using so-called overlap detectors was studied and shown to have the expected precision. (Less)

Development of a 3D imaging calorimeter in lanthanum bromide for gamma-ray space astronomy

The new generation of high light-output inorganic scintillators i.e. cerium-doped lanthanum(III) bromide (LaBr3:Ce) show a promising future in application as a space-based γ-ray calorimeter. Its internal qualities such as good energy resolution or radiation tolerance are well suited for detection of γ-rays in the MeV range, thus providing access to, so far, understudied questions in physics of nucleosynthesis, the active Sun or astrophysical compact objects. For this purpose, under the project of creating a new Compton telescope prototype, we have studied the response of a detection module comprising a 5×5 cm2 area and 1 cm thick LaBr3:Ce crystal scintillator coupled to a 64 channel multi-anode photomultiplier read out by the ASIC MAROC. Measurements with various radioactive sources have been compared with detailed GEANT4 simulations that include the tracking of the near-UV photons produced in the scintillation crystal. The localization of the first interaction point of incident γ-rays have been studied from the measured charge distributions using an artificial neural network. Together with the other measured properties, the position resolution that we obtain makes this detector module very interesting for the next generation of space telescopes operating in the medium-energy γ-ray domain.

DEVELOPMENT OF A DETECTOR (ALFA) TO MEASURE THE ABSOLUTE LHC LUMINOSITY AT ATLAS

The ATLAS collaboration plans to determine the absolute luminosity of the CERN LHC at Interaction Point 1 by measuring the trajectory of protons elastically scattered at very small angles (μrad). A scintillating fibre tracker system called ALFA (Absolute Luminosity For ATLAS) is proposed for this measurement. Detector modules will be placed above and below the LHC beam axis in roman pot units at a distance of 240 m on cach side of the ATLAS interaction point. They allow the detectors to approach the beam axis to millimeter distance. Overlap detectors also based on the scintillating fibre technology, will measure the precise relative position of the two detector modules, Results obtained during beam tests at DESY and at CERN validate the detectors design and demonstrate the achievable resolution. We also report about radiation hardness studies of the scintillating fibres to estimate the lifetime of the ALFA system at different operating conditions of the LHC. (Less)

Performance of CATIROC: ASIC for smart readout of large photomultiplier arrays

CATIROC (Charge And Time Integrated Read Out Chip) is a complete read-out chip manufactured in AustriaMicroSystem (AMS) SiGe 0.35 μm technology, designed to read arrays of 16 photomultipliers (PMTs). It is an upgraded version of PARISROC2 [1] designed in 2010 in the context of the PMm2 (square meter PhotoMultiplier) project [2]. CATIROC is a SoC (System on Chip) that processes analog signals up to the digitization and sparsification to reduce the cost and cable number. The ASIC is composed of 16 independent channels that work in triggerless mode, auto-triggering on the single photo-electron. It provides a charge measurement up to 400 photoelectrons (70 pC) on two scales of 10 bits and a timing information with an accuracy of 200 ps rms. The ASIC was sent for fabrication in February 2015 and then received in September 2015. It is a good candidate for two Chinese projects (LHAASO and JUNO). The architecture and the measurements will be detailed in the paper.