Readout Chip Research Articles

Measured effectiveness of deep N-well substrate isolation in a 65 nm pixel readout chip prototype

The same charge sensitive preamplifier and discriminator circuit with different isolation strategies has been tested to compare the isolation of both analog and digital circuits from the substrate of a 65 nm bulk CMOS process to the isolation of only digital circuits, tying analog ground locally to the substrate. This study will show that the circuit with analog on the substrate and digital in deep N-well has better noise isolation between analog and digital.

Test beam characterization of irradiated 3D pixel sensors

Due to the large expected instantaneous luminosity, the future HL-LHC upgrade sets strong requirements on the radiation hardness of the CMS detector Inner Tracker. Sensors based on 3D pixel technology, with its superior radiation tolerance, comply with these extreme conditions. A full study and characterization of pixelated 3D sensors fabricated by FBK is presented here. The sensors were bump-bonded to RD53A readout chips and measured at several CERN SPS test beams. Results on charge collection and efficiency, for both non-irradiated and irradiated up to 1016 neq/cm2 samples, are presented. Two main studies are described: in the first the behaviour of the sensor is qualified as a function of irradiation, while kept under identical conditions; in the second the response is measured under typical operating conditions.

The CLAS12 Silicon Vertex Tracker

For the 12 GeV upgrade of Jefferson Laboratory, a Silicon Vertex Tracker (SVT) has been designed for the CLAS12 spectrometer using single-sided microstrip sensors fabricated by Hamamatsu Photonics. The sensors have a graded angle design to minimize dead areas and a readout pitch of 156μm, with intermediate strips. Each double-sided SVT module hosts three daisy-chained sensors on each side with a full strip length of 33 cm. There are 512 channels per module, read out by four Fermilab Silicon Strip Readout (FSSR2) chips, featuring data-driven architecture, mounted on a rigid–flex hybrid board. The modules are assembled in a barrel configuration using a unique cantilevered geometry to minimize the amount of material in the tracking volume. This paper is focused on the design, qualification of the performance, and experience in operating and commissioning the tracker during the first year of the data taking.

First pump-probe-probe hard X-ray diffraction experiments with a 2D hybrid pixel detector developed at the SOLEIL synchrotron.

A new photon-counting camera based on hybrid pixel technology has been developed at the SOLEIL synchrotron, making it possible to implement pump-probe-probe hard X-ray diffraction experiments for the first time. This application relies on two specific advantages of the UFXC32k readout chip, namely its high frame rate (50 kHz) and its high linear count rate (2.6 × 106 photons s-1 pixel-1). The project involved the conception and realization of the chips and detector carrier board, the data acquisition system, the server with its specific software, as well as the mechanical and cooling systems. This article reports on in-laboratory validation tests of the new detector, as well as on tests performed at the CRISTAL beamline within the targeted experimental conditions. A benchmark experiment was successfully performed, showing the advantages of the pump-probe-probe scheme in correcting for drifts of the experimental conditions.

Performances of highly irradiated 3d and planar pixel sensors interconnected to the RD53A readout chip

The High Luminosity upgrade of the CERN Large Hadron Collider (HL-LHC) calls for new highly radiation tolerant silicon pixel sensors, capable of withstanding fluences up to 2.3 × 1016 neq/cm2 (1 MeV equivalent neutrons). In this paper results obtained in beam test experiments with 3D and planar pixel sensors interconnected with the RD53A readout chip are reported. RD53A is the first prototype in 65 nm technology issued by the RD53 collaboration for the future readout chip to be used in the upgraded pixel detectors. The interconnected modules have been tested in an electron beam at DESY, before and after irradiation, which was performed at the CERN IRRAD facility for the 3D sensors or at the KIT Irradiation Center for the planar sensors, up to an equivalent fluence of 1 × 1016 neq/cm2. The sensors were made by FBK foundry in Trento, Italy, and their development was done in collaboration with INFN (Istituto Nazionale di Fisica Nucleare, Italy). The analysis of the collected data shows hit detection efficiencies around 99% measured after irradiation. All results are obtained in the framework of the CMS R&D activities.

Multispectral photon-counting for medical imaging and beam characterization

We present the current status of our project of developing a photon counting detector for medical imaging. An example motivation lays in producing a monitoring and dosimetry device for boron neutron capture therapy, currently not commercially available. Our approach combines in-house developed detectors based on cadmium telluride or thick silicon with readout chip technology developed for particle physics experiments at CERN. Here we describe the manufacturing process of our sensors as well as the processing steps for the assembly of first prototypes. The prototypes use currently the PSI46digV2.1-r readout chip. The accompanying readout electronics chain that was used for first measurements will also be discussed. Finally we present an advanced algorithm developed by us for image reconstruction using such photon counting detectors with focus on boron neutron capture therapy. This work is conducted within a consortium of Finnish research groups from Helsinki Institute of Physics, Aalto University, Lappeenranta-Lahti University of Technology LUT and Radiation and Nuclear Safety Authority (STUK) under the RADDESS program of Academy of Finland.

An amperometric sensor readout chip and digital back-end with embedded integrator and redox potential generator for multi-analyte sensing applications

A fabricated amperometric sensor readout chip for interfacing with multiple electrochemical cells is presented. The chip incorporates a current integrator which can be used for charge determination and current accumulation for drift compensation. It also has a programmable redox potential generator. The front-end consists of a PMOS source input driven by a high gain OTA. It achieves very low input impedance and consequently, a wide current sensing range. The circuit utilizes pass elements acting as sensor enable for minimizing cross-talk. The current integrator utilizes a CCII+ with pre-settable gain. This is used to compensate for the sensor drift and degrading signal-noise-ratio whenever its enzyme is expended. The readout circuit was fabricated using TSMC 0.35 ​ ​μm technology. Digital interface was implemented onto an FPGA using the Altera 90 ​nm Cyclone II DE2 board. The system was tested using commercial two-electrode glucose and uric acid sensors, and a three-electrode uric acid biosensor. Experimentation confirms the functionality of the system using known analyte concentrations.

A Digital Readout IC for Microbolometer Imagers Offering Low Power and Improved Self-Heating Compensation

This paper presents a novel and power efficient readout architecture for uncooled microbolometers that offers adequate noise performance along with a circuit-based method for self-heating compensation. The proposed method employs an event-generation scheme and a time-mode readout chain to achieve dynamic mode of operation resulting in low power. The readout chain consists of a capacitive transimpedance amplifier (CTIA) based current-to-time converter followed by a two stage time-to-digital converter (TDC). The CTIA employs a novel integration scheme for time amplification along with a modified reset mechanism to achieve self-heating compensation. We also present a model to analyze the implications of time-mode readout on imager operation. An experimental readout chip, based on this approach, has been designed using a 130 nm bulk CMOS technology. The proposed architecture offers robust frontend processing and achieves a per channel power consumption of $66~\mu \text{W}$ , which is considerably lower than the most recently reported designs, while maintaining better than 10-mK readout noise equivalent temperature difference (NETD).

Compton-camera-based SPECT for thyroid cancer imaging.

Thyroid cancer is the most common type of endocrine-related cancer and the most common cancer in young women. Currently, single photon emission computed tomography (SPECT) and computed tomography (CT) are used with radioiodine scintigraphy to evaluate patients with thyroid cancer. The gamma camera for SPECT contains a mechanical collimator that greatly compromises dose efficiency and limits diagnostic sensitivity. Fortunately, the Compton camera is emerging as an ideal approach for mapping the distribution of radiopharmaceuticals inside the thyroid. In this preliminary study, based on the state-of-the-art readout chip Timepix3, we investigate the feasibility of using Compton camera for radiotracer SPECT imaging in thyroid cancer. A thyroid phantom is designed to mimic human neck, the mechanism of Compton camera-based event detection is simulated to generate realistic list-mode data, and a weighted back-projection method is developed to reconstruct the original distribution of the emission source. Study results show that the Compton camera can improve the detection efficiency for two or higher orders of magnitude comparing with the conventional gamma cameras. The thyroid gland regions can be reconstructed from the Compton camera measurements in terms of radiotracer distribution. This makes the Compton-camera-based SPECT imaging a promising modality for future clinical applications with significant benefits for dose reduction, scattering artifact reduction, temporal resolution enhancement, scan throughput increment, and others.

New luminescence lifetime macro-imager based on a Tpx3Cam optical camera.

The properties of a novel ultra-fast optical imager, Tpx3Cam, were investigated for macroscopic wide-field phosphorescent lifetime imaging (PLIM) applications. The camera is based on a novel optical sensor and Timepix3 readout chip with a time resolution of 1.6 ns, recording of photon arrival time and time over threshold for each pixel, and readout rate of 80 megapixels per second. In this study, we coupled the camera to an image intensifier, a 760 nm emission filter and a 50 mm lens, and with a super-bright 627nm LED providing pulsed excitation of a 18 × 18 mm sample area. The resulting macro-imager with compact and rigid optical alignment of its main components was characterised using planar phosphorescent O2 sensors and a resolution plate mask. Several acquisition and image processing algorithms were evaluated to optimise the system resolution and performance for the wide-field PLIM, followed by imaging a variety of phosphorescent samples. The new PLIM system looks promising, particularly for phosphorescence lifetime-based imaging of O2 in various chemical and biological samples.

Performance of new radiation-tolerant thin planar and 3D columnar n[formula omitted] on p silicon pixel sensors up to a maximum fluence of [formula omitted] n[formula omitted]/cm[formula omitted

The High Luminosity upgrade of the CERN Large Hadron Collider (HL-LHC) calls for new high radiation-tolerant solid-state pixel sensors, capable of surviving irradiation fluences up to a few 1016neq/cm2 at ∼3cm from the interaction point. The INFN ATLAS-CMS joint research activity, in collaboration with Fondazione Bruno Kessler, is aiming at the development of thin n+ on p type pixel sensors to be operated at the HL-LHC. The R&D covers both planar and 3D pixel devices made on substrates obtained by the Direct Wafer Bonding technique. The active thickness of the planar sensors studied in this paper is 100μm or 130μm, that of 3D sensors 130μm. First prototypes of hybrid modules, bump-bonded to the present CMS readout chips (PSI46 digital), have been characterized in beam tests. First results on their performance before and after irradiation up to a maximum fluence of ∼5×1015neq/cm2 are reported in this article.

Imaging of the Ruptured Aortic Aneurysm Wall and Atherosclerotic Plaque by High Resolution X-Ray Computed Tomography, the New Tool for Prevention of Acute Cardio-Vascular Events

Introduction - In the recent years a significant progress has been reached in the development of novel hybrid pixel detectors, which combine a sensor of high-Z material for efficient X-ray registration and a readout chip. This allows to achieve high spatial resolution and capability of instant signal processing.

Module development for the HL-LHC ATLAS ITk Pixel upgrade

For the Large Hadron Collider (LHC) Phase 2 upgrade ATLAS will replace its current inner detector with an all-silicon Inner Tracker (ITk) to achieve high performance in a very high occupancy and radiation environment. The ITk consists of strip and pixel modules. Here the focus is placed on the assembly and testing procedures needed to assure the quality of the pixel modules to be installed in the detector. Ongoing developments and activities are discussed, e.g. with a special focus on the effect of mechanical stress in the connection of sensor and readout chip in the module due to thermal effects.

High-resolution MEMS inertial sensor combining large-displacement buckling behaviour with integrated capacitive readout

Commercially available gravimeters and seismometers can be used for measuring Earth’s acceleration at resolution levels in the order of {mathrm{ng}}/sqrt {mathrm{Hz}} (where g represents earth’s gravity) but they are typically high-cost and bulky. In this work the design of a bulk micromachined MEMS device exploiting non-linear buckling behaviour is described, aiming for {mathrm{ng}}/sqrt {mathrm{Hz}} resolution by maximising mechanical and capacitive sensitivity. High mechanical sensitivity is obtained through low structural stiffness. Near-zero stiffness is achieved through geometric design and large deformation into a region where the mechanism is statically balanced or neutrally stable. Moreover, the device has an integrated capacitive comb transducer and makes use of a high-resolution impedance readout ASIC. The sensitivity from displacement to a change in capacitance was maximised within the design and process boundaries given, by making use of a trench isolation technique and exploiting the large-displacement behaviour of the device. The measurement results demonstrate that the resonance frequency can be tuned from 8.7 Hz–18.7 Hz, depending on the process parameters and the tilt of the device. In this system, which combines an integrated capacitive transducer with a sensitivity of 2.55 aF/nm and an impedance readout chip, the theoretically achievable system resolution equals 17.02 {mathrm{ng}}/sqrt {mathrm{Hz}}. The small size of the device and the use of integrated readout electronics allow for a wide range of practical applications for data collection aimed at the internet of things.

FPGA implementation of 10 G Ethernet-based DAQ systems for pixel detectors

High Energy Photon Source-Test Facility is a project to study and verify the feasibility of the key technologies which will be applied to that of High Energy Photon Source (HEPS). The pixel array detector is one of the most important components of synchrotron radiation detection. In order to meet the requirements of the X-ray detection of HEPS, it was asked to independently develop a pixel array detector prototype with an effective detection area larger than $$8 \times 8\,\text {cm}^{2}$$, a spatial resolution better than 200 $$\upmu $$m, a detectable energy range from 8 to 20 keV, and a frame rate higher than 1 kHz. The readout electronics system using the field-programmable gate array (FPGA) as its core of the digital logic makes the basic functions of the detector prototype feasibility by implementing all the configuration and data readout of the BPIX which is the dedicated pixel readout chip designed for Chinese next generation of synchrotron light source and working in the single-photon counting mode. Considering the large amount of data generated by pixel detectors and the demand for real-time data acquisition at higher frame rates, a firmware based on the TCP/IP protocol was developed in FPGA. The implementation of 1 G/10 G Ethernet hub firmware provides a method of processing multi-ports Gigabit data and improving bandwidth. The key idea is the conversion of the GMII/XGMII bus in 1 G/10 G Ethernet protocol and the Arbitrator module applying Round-Robin algorithms. The firmware converts and gathers TCP/IP frames from Gigabit network to 10-Gigabit network successfully. Through measurement, the bandwidth of the hub can reach 8.57 Gbps. A pixel detector integrated with 1 G/10 G Ethernet hub completes the readout of large flux data on 1.5 mega pixels detector at 1.2 kHz frame rate.

First annealing studies of irradiated silicon sensors with modified ATLAS pixel implantations

Planar silicon pixel sensors with modified n+-implantation shapes based on the IBL pixel sensor were designed in Dortmund. The sensors with a pixel size of 250 μm × 50 μm are produced in n+-in-n sensor technology. The charge collection efficiency should improve with electrical field strength maxima created by the different n+-implantation shapes. Therefore, higher particle detection efficiencies at lower bias voltages could be achieved. The modified pixel designs and the IBL standard design are placed on one sensor to test and compare the designs. The sensor can be read out with the FE-I4 readout chip. At the iWoRiD 2018, measurements of sensors irradiated with protons and neutrons respectively at different facilities were presented and showed incongruent results. Unintended annealing during irradiation was considered as an explanation for the observed differences in the hit detection efficiency for two neutron irradiated sensors. This hypothesis will be examined and confirmed in this work, presenting first annealing studies of sensors irradiated with neutrons in Ljubljana.

Towards MYTHEN III - prototype characterisation of MYTHEN III.0.2

The MYTHEN detector is a single photon counting microstrip detector with 50 μm pitch developed at Paul Scherrer Institute for powder diffraction experiments at the Swiss Light Source. After more than ten years of operation of MYTHEN II, a new readout chip MYTHEN III was designed in 110 nm UMC technology to upgrade the current detector. It is designed to improve all aspects, specifically noise performance, count rate capability, threshold dispersion and frame rate. Each strip in the MYTHEN III chip features a dual polarity front end consisting of a charge sensitive amplifier and a shaper with variable gain and shaping time, as well as three comparators and three gateable 24-bit counters. The internal counting logic allows for different modes of operation: energy-windowing, charge sharing suppression, count rate improvement and pump-probe with multiple time slots. The architecture of the chip and its characterisation results will be presented. The first two prototypes have been tested in the lab and at the synchrotron. The RMS noise is reduced to 178 electrons (−24% compared to MYTHEN II) and thanks to the three thresholds in the chip, we can detect multiple analog signals in the shaper at high photon flux and thereby reach a count rate of 25 MHz per strip. Based on these results, a full scale chip with 128 channels was developed and sent to production.

Serial powering and high hit rate efficiency measurement for the Phase 2 Upgrade of the CMS Pixel Detector

A serially powered pixel detector is the baseline choice for the High Luminosity upgrade of the inner tracker of the CMS experiment. A serial power distribution scheme, compared to parallel powering, requires less cable mass, offers higher power efficiency and is less susceptible to voltage transients. A prototype pixel readout chip has been designed for serial powering in 65 nm CMOS technology by the RD53 collaboration. Performance results from testing the prototype chip, called RD53A, are reported. The performance of RD53A operating in a chain consisting of four chips powered in series is compared with the performance under a conventional powering scheme. Additionally, the readout efficiency of RD53A in a high hit rate environment in different operation modes is presented for the first time. The results indicate that serial powering is a robust and reliable power distribution scheme.

Radiation hard active pixel sensor with [formula omitted][formula omitted][formula omitted] pixel size designed for capacitive readout with RD53 ASIC

A new concept for a capacitively coupled particle detector (CCPD) is described. Sensor and readout chips are attached using a small number of large bumps. A sensor chip for such a CCPD has been designed and tested. The sensor chip is based on the HVCMOS structure. Deep n-well is used as the charge collecting electrode. To allow strong amplification, which is necessary for chip to chip signal transmission, a novel CMOS based comparator with rail to rail output swing has been implemented in each pixel. The pixel outputs are connected to transmitting electrodes implemented in the top metal layer of the sensor chip. Using special address encoding a group of 16 pixels is connected to 8 transmitting electrodes. The pixel size is 25μm×50μm and the transmitting electrode pitch is 50μm×50μm. Therefore a standard HL-LHC readout chip developed by RD53 collaboration can be used for readout of the sensor.

Module development for the Phase-2 ATLAS ITk Pixel upgrade

For the high luminosity upgrade of the Large Hadron Collider (HL-LHC), the instantaneous luminosity is expected to reach unprecedented values, resulting in about 200 proton-proton interactions in a typical bunch crossing. To cope with the resultant increase in occupancy, bandwidth and radiation damage, the ATLAS Inner Detector will be replaced by an all-silicon system, the Inner Tracker (ITk). The innermost part of ITk will consist of a state-of-the-art pixel detector, with an active area of about 14 m2, which will provide tracking capability up to |η|=4. Detector requirements in terms of radiation hardness and occupancy, as well as thermal performance depend strongly on the distance from the interaction region. Therefore, the innermost layer will feature 3D silicon sensors, due to their inherent radiation hardness and low power consumption, while the remaining layers will employ planar silicon sensors with thickness ranging from 100 μm to 150 μm. All hybrid detector modules will be read out by novel ASICs, implemented in 65 nm CMOS technology and thinned to 150 μm, which will be connected to the silicon sensors using bump bonding. With the recent arrival of the first readout chip prototype, the RD53A chip, prototype modules are being built to study sensor and chip properties, thermal performance, as well as bump bonding yield in lab measurements and beam test campaigns. Irradiation studies are ongoing. The report will present latest results from the module characterization measurements both before and after irradiation.