A. Comerma

Front End ASIC design for SiPM readout

A Front End ASIC for the readout of Silicon Photo-Multipliers is presented with the following features: wide dynamic range, high speed, multi channel, low input impedance current preamplifier, low power (7mW per channel), DC coupled input with common mode voltage control and separated timing and charge signal output. A detailed description of the SiPM modeling and parameter extraction is also included allowing the emulation of the signal generated by different commercial devices in the design simulation stage. Current prototype is the first step for a more complex mixed signal design including more channels, analog processing and digital outputs, thus reducing power consumption and increasing integration. This prototype includes basic blocks for 3 channels with: preamplifier with two separate signal paths and fast current discriminator with digital output.

FlexToT - Current mode ASIC for readout of common cathode SiPM arrays

A front end application specific integrated circuit (ASIC) for the readout of common cathode Silicon Photo-Multipliers arrays is presented with the following features: wide dynamic range, high speed, multi channel, low input impedance current amplifier, low power (≈10mW per channel), common cathode connection, directly coupled input with common mode voltage control and separated timing and charge signal output.A 16 channel prototype with 16 independent outputs for energy and pile-up detection and a single fast timing output is described. The low jitter current mode processing together with a configurable differential current mode logic (CML) output provides a timing signal suitable for Time of Flight (TOF) applications, such as TOF-PET (Positron Emission Tomography). Each channel delivers a digital output of a Time Over Threshold (TOT) type with a pulse width proportional to peak current (charge) input. The current mode input stage features a novel double feedback; a low speed feedback loop keeps input node voltage constant while a higher speed feedback loop keeps input impedance low. Dedicated circuitry allows SiPM high over-voltage operation, thus maximizing Photon Detection Efficiency (PDE) and timing resolution. Design was submitted in June 2012 in Austria Microsystems (AMS) 0.35 μm HBT BiCMOS technology and is under test.

Readout electronics for low dark count pixel detectors based on Geiger mode avalanche photodiodes fabricated in conventional CMOS technologies for future linear colliders

High sensitivity and excellent timing accuracy of the Geiger mode avalanche photodiodes make them ideal sensors as pixel detectors for particle tracking in high energy physics experiments to be performed in future linear colliders. Nevertheless, it is well known that these sensors suffer from dark counts and afterpulsing noise, which induce false hits (indistinguishable from event detection) as well as an increase in the necessary area of the readout system. In this work, we present a comparison between APDs fabricated in a high voltage 0.35 mm and a high integration 0.13 mm commercially available CMOS technologies that has been performed to determine which of them best fits the particle collider requirements. In addition, a readout circuit that allows low noise operation is introduced. Experimental characterization of the proposed pixel is also presented in this work.

Readout electronics for low dark count Geiger mode avalanche photodiodes fabricated in conventional HV-CMOS technologies for future linear colliders

This work presents low noise readout circuits for silicon pixel detectors based on Geiger mode avalanche photodiodes. Geiger mode avalanche photodiodes offer a high intrinsic gain as well as an excellent timing accuracy. In addition, they can be compatible with standard CMOS technologies. However, they suffer from a high intrinsic noise, which induces false counts indistinguishable from real events and represents an increase of the readout electronics area to store the false counts. We have developed new front-end electronic circuitry for Geiger mode avalanche photodiodes in a conventional 0.35 μm HV-CMOS technology based on a gated mode of operation that allows low noise operation. The performance of the pixel detector is triggered and synchronized with the particle beam thanks to the gated acquisition. The circuits allow low reverse bias overvoltage operation which also improves the noise figures. Experimental characterization of the fabricated front-end circuit is presented in this work.

Evaluation of the FlexToT ASIC on the readout of SiPM matrices and scintillators for PET

We have designed FlexToT, a flexible application specific integrated circuit (ASIC) using time-over-threshold (ToT) techniques for the readout of silicon photomultiplier (SiPM) arrays in positron emission tomography (PET) detectors. The FlexToT ASIC accommodates 16 independent channels in a small die size (2.93 mm by 2.54 mm) with low power consumption (10 mW per channel), providing output signals whose duration is proportional to the current amplitude at its inputs. The threshold, gain and other parameters can be independently set for each channel in a flexible configuration that can be tailored to different applications and devices. Herein we present the results on the evaluation of the FlexToT ASIC operating as front-end electronics for SiPM arrays S11828-3344M from Hamamatsu (Japan) coupled to LYSO:Ce scintillators in a simple PET tomograph demonstrator. Each detector block is composed of a LYSO:Ce matrix coupled to 4 SiPM arrays in a 2×2 mosaic, totaling 64 pixels (8×8) which are read out by 4 FlexToT ASICs. Using this demonstrator we have obtained PET images of 22Na point sources with spatial resolutions better than 2 mm full width at half maximum (FWHM), validating our design of the FlexToT ASIC on the readout of SiPM matrices and scintillators in PET applications.

Performance of FlexToT Time Based PET Readout ASIC for Depth of Interaction Measurements

J. Trenadoa∗, J. M. Celab, A. Comermaa†, D. Gascona, R. Graciania, L. Freixasb, J. Marinb, G. Martínezb, R. Masachsa, J.M. Perezb, P. Ratob, D. Sancheza, A. Sanuya, I. Sarasolab a University of Barcelona, Spain b CIEMAT, Spain E-mail: jtrenado@ecm.ub.edu, josemanuel.cela@ciemat.es, comerma@physi.uni-heidelberg.de, dgascon@ecm.ub.edu, graciani@ecm.ub.edu, lluis.freixas@ciemat.es, jesus.marin@ciemat.es, gustavo.martinez@ciemat.es, rmasachs@ecm.ub.edu, jm.perez@ciemat.es, pedro.rato@ciemat.es, dsanchez@ecm.ub.edu, asanuy@ecm.ub.edu, iciar.sarasola@ciemat.es

FIB-SEM as a tool for characterizing single-photon detectors

Single-photon avalanche diodes (SPADs) are nowadays the most consolidate solid-state alternative to photomultiplier tubes and time-correlated single-photon counting. Optical benches are used for the characterization of the noise figures of these detectors, including dark count, afterpulsing effects and cross-talk. With accurate optical setups it is possible to obtain resolutions down to 5 microns, but with todays technologies, this spot size can cover more than one single pixel. Moreover, on other common and envisaged applications like particle detection in Nuclear and High Energy Physics or as silicon photomultipliers for Cerenkov telescopes, this does not allow to observe what happens when a charge is generated between consecutive pixels. This work presents the innovative characterization of single-photon detectors with the aid of the electron beam generated in a dual beam FIB/SEM apparatus. A simple setup allows a very good control of the dose and the spot down to 5 nm at 30 keV, The characterization has been proven in photodetectors fabricated in a standard CMOS technology. The results have been validated by comparison with those obtained by optical setups, with simulation with PENELOPE (Penetration and Energy Loss of Positrons and Electrons) and by technology simulations with ISE-tCAD.

Scintillator Pad Detector: Very Front End Electronics. Design and Pre‐Series

The SPD (Scintillator Pad Detector) is a part of LHCb calorimeter which is designed to distinguish electrons and photons for this first level trigger. This detector is a plastic scintillator layer, divided in about 6000 cells of different size to obtain better granularity near the beam. Charged particles will produce, and photons will not, ionisation on the scintillator. This ionisation generates a light pulse that is collected by a Wavelength Shifting (WLS) fibre that is twisted inside the scintillator cell. The light is transmitted through a clear fibre to the readout system. For cost reduction, these 6000 cells are divided in groups using a MAPMT of 64 channels for receiving information in the readout system. The signal outing the SPD PMTs is rather unpredictable as a result of the low photostatistics, 20–30 photoelectrons per MIP, and the response of the WLS fibre, which has low decay time. Then, the signal processing must be performed by first integrating the total charge and later subtracting to avo...