Radiation tolerance of a column parallel CMOS sensor with high resistivity epitaxial layer

CMOS Monolithic Active Pixel Sensors (MAPS) demonstrated excellent performances in the field of charged particle tracking. Among their strong points are an single point resolution few μm, a light material budget of 0.05% X0 in combination with a good radiation tolerance and high rate capability. Those features make the sensors a valuable technology for vertex detectors of various experiments in heavy ion and particle physics. To reduce the load on the event builders and future mass storage systems, we have developed algorithms suited for preprocessing and reducing the data streams generated by the MAPS. This real-time processing employs remaining free resources of the FPGAs of the readout controllers of the detector and complements the on-chip data reduction circuits of the MAPS.

The features of the 180nm TowerJazz1 CMOS technology allow for the first time the use of CMOS Monolithic Active Pixel Sensors (MAPS) under the harsh operational conditions of the LHC experiments. The stringent requirements of the ALICE Inner Tracking System (ITS) in terms of material budget, radiation hardness, readout speed and a low power consumption have thus lead to the choice of MAPS as baseline technology option for the recently approved upgrade of the ITS and are the key drivers for R&D efforts on basic transistor and Explorer and MIMOSA pixel sensor prototypes produced in TowerJazz technology. Though the radiation loads expected for the ITS are below those of ATLAS and CMS, it is however necessary to assess the radiation hardness for ITS MAPS prototypes. Total Ionizing Dose (TID) radiation hardness has been established for basic transistor structures using a 60keV X-ray machine. The main operational characteristics and detection properties such as noise, charge collection efficiency and signal over noise ratio of Explorer-0 and MIMOSA32 and MIMOSA34 pixel sensor prototypes have been studied using X-rays (55Fe) and test beams at CERN and DESY before and after Non Ionizing Energy Loss (NIEL) and TID irradiation. In this paper the results of these R&D activities will be presented and discussed.

This paper reviews the development of CMOS Monolithic Active Pixel Sensors (MAPS) for future vertex detectors. MAPS are developed in a standard CMOS technology. In the imaging field, where the technology found its first applications, they are also known as CMOS Image Sensors. The use of MAPS as a detector for particle physics was first proposed at the end of 1999. Since then, their good performance in terms of spatial resolution, efficiency, radiation hardness have been demonstrated and work is now well under way to deliver the first MAPS-based vertex detectors.

Development of a triple well CMOS MAPS device with in-pixel signal processing and sparsified readout capabilities

CMOS Monolithic Active Pixel Sensors (MAPS) have demonstrated excellent performance as tracking detectors for charged particles. They provide an outstanding spatial resolution (a few μm), a detection efficiency of ≳99.9%, very low material budget (0.05% X0) and good radiation tolerance (≳ 1 Mrad, ≳ 1014 neq/cm2) [1]. This recommends them as an interesting technology for various applications in heavy ion and particle physics.For the vertex detectors of CBM and ALICE, we are aiming at developing large scale sensors with an integration time of 30μs. Reaching this goal is eased by features available in CMOS-processes with 0.18μm feature size. To exploit this option, some sensor designs have been migrated from the previously used 0.35μm processes to this novel process. We report about our first findings with the devices obtained with a focus on noise and the tolerance to ionizing radiation.

A general purpose beam telescope of new generation has been constructed and tested. Four reference planes of the telescope are based on CMOS Monolithic Active Pixel Sensors (MAPS), thinned down to less than 100 microns. Noise optimized, high precision tracking pixel sensors have been designed and fabricated for this application using AMS 0.35 OPTO process. Single sensor consists of 512times512 pixel array with a pitch of 10 mum, providing an active area of 5times5 mm2. Measured signal-to-noise ratio for minimum ionizing particle (MIP) is more than 27 at room temperature and extrapolated single point (2D) resolution is below 1 mum. Use of such sensors for beam telescope provide an attractive solution for high precision tracking of minimum ionizing particles even in case of their relatively low energy. Telescope tracking performance study, including beam tests results with hundreds GeV pions is presented. Comparison of sensors fabricated using standard (14 mum thick epitaxy) and experimental (20 mum epitaxy) wafers is also discussed.

Response of the MIMOSIS-1 CMOS Monolithic Active Pixel Sensor to particle beams with different dE/dx

The Heavy Flavor Tracker (HFT) is a recently installed micro-vertex detector upgrade to the STAR experiment at RHIC, consisting of three subsystems with various technologies of silicon sensors arranged in 4 concentric cylinders. The two innermost layers of the HFT close to the beam pipe, the Pixel (“PXL”) subsystem, employ CMOS Monolithic Active Pixel Sensor (MAPS) technology that integrate the sensor, front-end electronics, and zero-suppression circuitry in one silicon die. This paper presents selected characteristics of the PXL detector part of the HFT and the hardware, firmware and software associated with the readout system for this detector.

ALICE (A Large Ion Collider Experiment) is the heavy-ion experiment at the Large Hadron Collider (LHC) at CERN. As an important part of its upgrade plans, the ALICE experiment will schedule the installation of a new Inner Tracking System (ITS) during the Long Shutdown 2 (LS2) of the LHC. The new ITS layout will consist of seven concentric layers, $\approx$ 12.5 Gigapixel camera covering about 10m$^2$ with Monolithic Active Pixel Sensors (MAPS). This choice of technology has been guided by the tight requirements on the material budget of 0.3$\%$ X/X$_0$ per layer for the three innermost layers and backed by the significant progress in the field of MAPS in recent years. The technology initially chosen for the ITS upgrade is the TowerJazz 180 nm CMOS Technology. It offers a standard epitaxial layer of 15 - 18 $\mu$m with a resistivity between 1 and 5 k$\Omega$~cm$^{-1}$ and a gate oxide thickness below 4 nm, thus being more robust to Total Ionizing Dose (TID). The main subject of this thesis is to implement a novel digital pixel readout architecture for MAPS. This thesis aims to study this novel readout architecture as an alternative to the rolling-shutter readout. However, this must be investigated through the study of several chip readout architectures during the R$\&$D phase. Another objective of this thesis is the study and characterization of TowerJazz, if it meets the Non-Ionizing Energy Loss (NIEL) and Single Event Effects (SEE) of the ALICE ITS upgrade program. Other goals of this thesis are: Implementation of the top-down flow for this CMOS process and the design of multiple readouts for different prototypes up to the assembly of a full-scale prototype. Characterization of the radiation hardness and SEE of the chips submitted to fabrication. Characterization of full custom designs using analog simulations and the generation of digital models for the simulation chain needed for the verification process. \item Implementation and study of different digital readouts to meet the ITS upgrade program in integration time, pixel size and power consumption, from the conceptual idea, production and fabrication phase. SChapter 1 is a brief overview of CERN, the LHC and the detectors complex. The ALICE ITS will be explained, focusing on the ITS upgrade in terms of detector needs and design constraints. Chapter 2 explains the properties of silicon detectors and the detector material and the principles of operation for MAPS. Chapters 3 and 4 describe the ALPIDE prototypes and their readout based on MAPS; this forms the central part of this work, including the multiple families of pixel detectors fabricated in order to reach the final design for the ITS. The ALPIDE3/pALPIDE3B chip, the latest MAPS chip designed, will be explained in detail, as well focusing in the matrix digital readout. In chapter 5 the noise measurements and its characterization are presented including a brief summary of detector response to irradiation with soft X-rays, sources and particle beams. on the ITS upgrade in terms of detector needs and design constraints. Chapter 2 explains the properties of silicon detectors and the detector material and the principles of operation for MAPS. Chapters 3 and 4 describe the ALPIDE prototypes and their readout based on MAPS; this forms the central part of this work, including the multiple families of pixel detectors fabricated in order to reach the final design for the ITS. The ALPIDE3/pALPIDE3B chip, the latest MAPS chip designed, will be explained in detail, as well focusing in the matrix digital readout. In chapter 5 the noise measurements and its characterization are presented including a brief summary of detector response to irradiation with soft X-rays, sources and particle beams.

ID: 139 Monte Carlo simulations for imaging in proton therapy

ALICE plans an upgrade of its Inner Tracking System for 2018. The development of a monolithic active pixel sensor for this upgrade is described. The TowerJazz 180 nm CMOS imaging sensor process has been chosen as it is possible to use full CMOS in the pixel due to the offering of a deep pwell and also to use different starting materials.The ALPIDE development is an alternative to approaches based on a rolling shutter architecture, and aims to reduce power consumption and integration time by an order of magnitude below the ALICE specifications, which would be quite beneficial in terms of material budget and background. The approach is based on an in-pixel binary front-end combined with a hit-driven architecture. Several prototypes have already been designed, submitted for fabrication and some of them tested with X-ray sources and particles in a beam. Analog power consumption has been limited by optimizing the Q/C of the sensor using Explorer chips. Promising but preliminary first results have also been obtained with a prototype ALPIDE. Radiation tolerance up to the ALICE requirements has also been verified.

The use of CMOS Monolithic Active Pixel Sensors for high precision minimum ionizing particle tracking has been proven to be a viable and powerful novel experimental technique. In this approach a lightly doped thin and partially depleted silicon epitaxial layer is used as a radiation sensitive detector volume. The readout electronics circuitry is integrated directly on top of epitaxy using standard commercial CMOS process. For the pixel pitch of 20/spl mu/m particle tracking precision of below 2/spl mu/m and full efficiency have been measured in the past. In this work measurements with CMOS MAPS fabricated on non-epitaxial, high resistivity substrate are presented. Efficient and performing MIP tracking is demonstrated, also for a large 40/spl mu/m pixel readout pitch. These results proves that the use of epitaxial substrate for MAPS fabrication is not mandatory, opening much larger choice of possible CMOS processes in the future.

Monolithic active pixel sensors (MAPS) in a VLSI CMOS technology

Advantages of a vertical integration process in the design of DNW MAPS

The MIMOSA pixel sensors developed in Strasbourg have demonstrated attractive features for the detection of charged particles in high energy physics. So far, full-size sensors have been prototyped only with analog readout, which limits the output rate to about 1000 frames/second. The new MIMOSA 26 sensor provides a 2.2 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> sensitive surface with an improved readout speed of 10,000 frames/second and data throughput compression. It incorporates pixel output discrimination for binary readout and zero suppression micro-circuits at the sensor periphery to stream only fired pixel out. The sensor is back from foundry since february 2009 and has being characterized in laboratory and in test beam. The temporal noise is measured around 13-14 e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> and an operation point corresponding to an efficiency of 99.5±0.1 % for a fake rate of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> per pixel can be reached at room temperature. MIMOSA 26 equips the final version of the EUDET beam telescope and prefigures the architecture of monolithic active pixel sensors (MAPS) for coming vertex detectors (STAR, CBM and ILC experiments) which have higher requirements. Developments in the architecture and technology of the sensors are ongoing and should allow to match the desired readout speed and radiation tolerance. Finally, the integration of MAPS into a micro-vertex detector is addressed. A prototype ladder equipped, on both sides, with a row of 6 MIMOSA 26-like sensors is under study, aiming for a total material budget about 0.3% X <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> .