Angelo Rivetti

A low-power 10 bit ADC in a 0.25 /spl mu/m CMOS: design considerations and test results

This paper presents the design and test of a low power analog to digital converter implemented in a commercial 0.25 /spl mu/m CMOS technology. The circuit has been developed to serve as a building block in multi-channel data acquisition systems for high energy physics (HEP) applications. Therefore medium resolution (10 bits), very low power consumption and high modularity are the key features of the design. In HEP experiments the resistance of the electronics to the ionizing radiation is often a primary issue. Hence the ADC has been laid-out using a radiation tolerant approach. The test results show that the chip operates as a full 10 bit converter up to a clock frequency of 30 MHz. No degradation in performance has been measured after a total dose of 10 Mrd (SiO/sub 2/).

A 64-channel ASIC for TOFPET applications

A 64-channel ASIC for TOF PET imaging is presented. The circuit provides time and energy measurements of events produced by a SiPM coupled to a L(Y)SO fast scintillator. This ASIC is developed in the framework of the EndoTOFPETUS collaboration as an option for the readout of external 200×200 mm plate detector, which consists of 3×3×15 mm crystals and 3×3 mm (active area) SiPMs. Using the chip with non-segmented and/or higher light yield crystals is possible. The same applies for photodetectors with different gain, polarity, or even higher dark count rate. The targeted 200 ps timing resolution for the system and the need for a low power consumption have driven the choice of a closed-loop amplifier input stage and a 50 ps time binning TDC based on analogue interpolation. A power consumption between 5 to 10 mW per channel is expected to guarantee a SNR of at least 20 dB for the single photon, using a SiPM with 320 pF terminal capacitance.

The GBLD: a radiation tolerant laser driver for high energy physics applications

The GigaBit Laser Driver (GBLD) is a radiation tolerant ASIC which is part of the GigaBit Transceiver (GBT) chipset. It is aimed to drive both edge emitting and VCSEL laser diodes at a data rate in excess of 5 Gb/s. The GBLD can provide a modulation current up to 24 mA and a bias current up to 43 mA. Pre- and de-emphasis functions are implemented to compensate for high external capacitive loads and asymmetric laser response. The chip is designed in a 130 nm CMOS technology and is powered by a single 2.5 V supply.

A large dynamic range radiation-tolerant analog memory in a quarter-micron CMOS technology

An analog memory prototype containing 8*128 cells has been designed in a commercial quarter-micron CMOS process. The aim of this work is to investigate the possibility of designing large dynamic range mixed-mode switched capacitor circuits for high-energy physics (HEP) applications in deep submicron CMOS technologies. Special layout techniques have been used to make the circuit radiation tolerant. The memory cells employ gate-oxide capacitors for storage, permitting a very high density. A voltage write-voltage read architecture has been chosen to minimize the sensitivity to absolute capacitor values. The measured input voltage range is 2.3 V (the power supply voltage V/sub DD/ is equal to 2.5 V), with a linearity of almost 8 bits over 2 V. The dynamic range is more than 11 bits. The pedestal variation is /spl plusmn/0.5 mV peak-to-peak. The noise measured, which is dominated by the noise of the measurement setup, is around 0.8 mV rms. The characteristics of the memory have been measured before irradiation and after 100 kGy (SiO/sub 2/), and they do not degrade after irradiation.

A low-power low-noise synchronous pixel front-end chain in 65 nm CMOS technology with local fast ToT encoding and autozeroing for extreme rate and radiation at HL-LHC

A low-power and low-noise synchronous front-end chain in a commercial 65 nm CMOS technology suitable for the future pixel upgrades at the CERN Large Hadron Collider (LHC) is presented. A shaper-less Charge-Sensitive Amplifier (CSA) with constant current feedback provides triangular pulse shaping for linear Time-over-Threshold (ToT) charge measurement. The sensor leakage current is compensated by the same feedback network. A track-and-latch voltage comparator is adopted for the hit discrimination. The hit generation is synchronized with a 40 MHz clock, minimizing time-walk issues in the time-stamp assignment. Fast ToT charge encoding up to 8-bit resolution can be retrieved at the pixel level exploiting a high-frequency self-generated clock signal. This is obtained by turning the latch into a voltage-controlled oscillator (VCO) using asynchronous logic. Pixel-to-pixel threshold variations are compensated by means of an autozeroed scheme, thus avoiding the need of a on-pixel D/A converter. An array of 8 × 8 cells with 50 μm × 50 μm pixel size has been prototyped. Design specifications, implementation and test results are discussed.

Characterization of the ALICE Silicon Drift Detectors using an infrared laser

The Inner Tracking System of the ALICE experiment at LHC uses Silicon Drift Detectors in two cylindrical layers located at radial distance of ≈ 15 and ≈ 24 cm from the beam axis. The spatial resolution of silicon drift detectors can be strongly affected by inhomogeneities of the doping concentration, temperature effects and non-linearity of the drift potential distribution. Before the detector commissioning, an extensive study and characterization of all the produced detectors has been performed. For this purpose, a specific measuring station, based on a laser mapping system, has been developed.

INSIDE in-beam positron emission tomography system for particle range monitoring in hadrontherapy

Abstract. The quality assurance of particle therapy treatment is a fundamental issue that can be addressed by developing reliable monitoring techniques and indicators of the treatment plan correctness. Among the available imaging techniques, positron emission tomography (PET) has long been investigated and then clinically applied to proton and carbon beams. In 2013, the Innovative Solutions for Dosimetry in Hadrontherapy (INSIDE) collaboration proposed an innovative bimodal imaging concept that combines an in-beam PET scanner with a tracking system for charged particle imaging. This paper presents the general architecture of the INSIDE project but focuses on the in-beam PET scanner that has been designed to reconstruct the particles range with millimetric resolution within a fraction of the dose delivered in a treatment of head and neck tumors. The in-beam PET scanner has been recently installed at the Italian National Center of Oncologic Hadrontherapy (CNAO) in Pavia, Italy, and the commissioning phase has just started. The results of the first beam test with clinical proton beams on phantoms clearly show the capability of the in-beam PET to operate during the irradiation delivery and to reconstruct on-line the beam-induced activity map. The accuracy in the activity distal fall-off determination is millimetric for therapeutic doses.

An overview of the Clear-PEM breast imaging scanner

We present an overview of the Clear-PEM breast imaging scanner. Clear-PEM is a unique dual-head Positron Emission Mammography scanner using APD-based detector modules that are capable of measuring depth-of-interaction (DOI) with a resolution of 2 mm in 20 mm long LYSO:Ce crystals. Such capability leads to an image spatial resolution of 1.2 mm and a high efficiency, foreseeing the detection of 3 mm breast lesions in less than 7 minutes exams. The full system comprises 192 detector modules in a total of 6144 LYSO:Ce crystals and 384 32-pixel APD arrays readout by ASICs with 192 input channels that represents an unprecedented level of integration in PET systems. Throughout the project and besides the detector module, we had developed dedicated Frontend and Data Acquisition electronics, the mechanical design and construction of the detector heads and the robotic gantry, as well as all the software that include calibration (energy, time and DOI), normalization and image reconstruction algorithms. In this work we will discuss the developments and present the commissioning results of the detector before the beginning of the clinical trials program, scheduled for the end of the present year.

Characterization of the Clear-PEM breast imaging scanner performance

We present results on the characterization of the Clear-PEM breast imaging scanner. Clear-PEM is a dual-head Positron Emission Mammography scanner using APD-based detector modules that are capable of measuring depth-of-interaction (DOI) with a resolution of 2 mm in LYSO:Ce crystals. The full system comprises 192 detector modules in a total of 6144 LYSO:Ce crystals and 384 32-pixel APD arrays readout by ASICs with 192 input channels, which represents an unprecedented level of integration in APD-based PET systems. The system includes Frontend and Data Acquisition electronics and a robotic gantry for detector placement and rotation. The software implements calibration (energy, time and DOI), normalization and image reconstruction algorithms. In this work, the scanner main technical characteristics, calibration strategies and the spectrometric performance in a clinical environment are presented. Images obtained with point sources and extended uniform sources are also presented. The first commissioning results show 99.7% active channels. After calibration, the dispersion of the channels absolute gain is 15.3%, which demonstrate that despite the large number of channels the system is rather uniform. The mean energy resolution at 511 keV is 15.9% for all channels, and the mean DOI constant is 5.9%/mm, which is consistent with a 2 mm DOI resolution, or better. The coincidence time resolution at 511 keV, for a energy window between 400 and 600 keV, is 5.2 ns FWHM. The image resolution measured with point sources was found to be of the order of 1.3 mm FWHM. The DOI capability was found to have a strong impact on the image sharpness. Images of extended uniform 68Ge sources, corrected for sensitivity and for the artifacts due detector dead spaces, have good uniformity. First clinical breast images are presented.

Online proton therapy monitoring: clinical test of a Silicon-photodetector-based in-beam PET

Particle therapy exploits the energy deposition pattern of hadron beams. The narrow Bragg Peak at the end of range is a major advantage but range uncertainties can cause severe damage and require online verification to maximise the effectiveness in clinics. In-beam Positron Emission Tomography (PET) is a non-invasive, promising in-vivo technique, which consists in the measurement of the β+ activity induced by beam-tissue interactions during treatment, and presents the highest correlation of the measured activity distribution with the deposited dose, since it is not much influenced by biological washout. Here we report the first clinical results obtained with a state-of-the-art in-beam PET scanner, with on-the-fly reconstruction of the activity distribution during irradiation. An automated time-resolved quantitative analysis was tested on a lacrimal gland carcinoma case, monitored during two consecutive treatment sessions. The 3D activity map was reconstructed every 10u2009s, with an average delay between beam delivery and image availability of about 6u2009s. The correlation coefficient of 3D activity maps for the two sessions (above 0.9 after 120u2009s) and the range agreement (within 1u2009mm) prove the suitability of in-beam PET for online range verification during treatment, a crucial step towards adaptive strategies in particle therapy.