The upgrade of the ATLAS 1 tracking detector for the High-Luminosity Large Hadron Collider (LHC) at CERN requires novel radiation hard silicon sensor technologies. Significant effort has been put ...into the development of monolithic CMOS sensors but it has been a challenge to combine a low capacitance of the sensing node with full depletion of the sensitive layer. Low capacitance brings low analog power. Depletion of the sensitive layer causes the signal charge to be collected by drift sufficiently fast to separate hits from consecutive bunch crossings (25 ns at the LHC) and to avoid losing the charge by trapping. This paper focuses on the characterization of charge collection properties and detection efficiency of prototype sensors originally designed in the framework of the ALICE Inner Tracking System (ITS) upgrade 2. The prototypes are fabricated both in the standard TowerJazz 180nm CMOS imager process 3 and in an innovative modification of this process developed in collaboration with the foundry, aimed to fully deplete the sensitive epitaxial layer and enhance the tolerance to non-ionizing energy loss. Sensors fabricated in standard and modified process variants were characterized using radioactive sources, focused X-ray beam and test beams before and after irradiation. Contrary to sensors manufactured in the standard process, sensors from the modified process remain fully functional even after a dose of 1015neq/cm2, which is the the expected NIEL radiation fluence for the outer pixel layers in the future ATLAS Inner Tracker (ITk) 4.
Abstract
Depleted Monolithic Active Pixel Sensor (DMAPS) sensors developed in the Tower Semiconductor 180 nm CMOS imaging process have been designed in the context of the ATLAS ITk upgrade Phase-II ...at the HL-LHC and for future collider experiments. The “MALTA-Czochralski (MALTA-Cz)” full size DMAPS sensor has been developed with the goal to demonstrate a radiation hard, thin CMOS sensor with high granularity, high hit-rate capability, fast response time and superior radiation tolerance. The design targets radiation hardness of > 10
15
(1 MeV) n
eq
/cm
2
and 100 Mrad TID. The sensor shall operate as tracking sensor with a spatial resolution of ≈ 10 μm and be able to cope with hit rates in excess of 100 MHz/cm
2
at the LHC bunch crossing frequency of 40 MHz. The 512 × 512 pixel sensor uses small collection electrodes (3.5 μm) to minimize capacitance. The small pixel size (36.4 × 36.4 μm
2
) provides high spatial resolution. Its asynchronous readout architecture is designed for high hit-rates and fast time response in triggered and trigger-less detector applications. The readout architecture is designed to stream all hit data to the multi-channel output which allows an off-sensor trigger formation and the use of hit-time information for event tagging.
The sensor manufacturing has been optimised through process adaptation and special implant designs to allow the manufacturing of small electrode DMAPS on thick high-resistivity p-type Czochralski substrate. The special processing ensures excellent charge collection and charge particle detection efficiency even after a high level of radiation. Furthermore the special implant design and use of a Czochralski substrate improves the sensor's time resolution. This paper presents a summary of sensor design optimisation through process and implant choices and TCAD simulation to model the signal response. Beam and laboratory test results on unirradiated and irradiated sensors have shown excellent detection efficiency after a dose of 2 × 10
15
1 MeV n
eq
/cm
2
. The time resolution of the sensor is measured to be
σ
= 2 ns.
Fiber optic sensors in the ATLAS Inner Detector Scherino, L.; Schioppa, E.J.; Arapova, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2022, Letnik:
1029
Journal Article
Recenzirano
Odprti dostop
A prototype system of Fiber Optic Sensors (FOS) for the accurate measurement of temperature and relative humidity, has been installed inside the Inner Detector volume of the ATLAS experiment at the ...LHC. The goal is to evaluate the behavior of the technology against radiation effects, and possibly to assess its suitability for future collider experiments, starting from HL-LHC. It follows the description of the work that has led to the choice of the sensors, their testing and calibration in the laboratory, their successive installation and operation in ATLAS, and the development of the data acquisition chain. The first results on performance are reported.
X-ray transition radiation detectors (TRDs) are used for particle identification in both high energy physics and astroparticle physics. In most of the detectors, emission of the X-ray transition ...radiation (TR) starts at Lorentz factors above γ∼500 and reaches saturation at γ∼2÷3⋅103. However, many experiments require particle identification up to γ∼105, which is very difficult to achieve with conventional detectors. Semiconductor pixel detectors offer a unique opportunity for precise simultaneous measurements of spectral and angular parameters of TR photons. Test beam studies of the energy and the angular distributions of TR photons emitted by electrons and muons of different momenta crossing several types of radiators were performed at the CERN SPS with a 480 μm thick silicon detector bonded to a Timepix3 chip. High resolution images of the energy−angle phase space of the TR produced by different radiators were obtained and compared with MC simulations. The characteristic interference patterns are in agreement with the theoretical models with an unprecedented level of details. The studies presented in this paper also show that simultaneous measurements of both the energy and the emission angles of the TR X-rays could be used to enhance the particle identification performances of TRDs.
Measurement results of the MALTA monolithic pixel detector Schioppa, E.J.; Asensi Tortajada, I.; Berdalovic, I. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
958
Journal Article
Recenzirano
MALTA is a full scale monolithic pixel detector implemented in TowerJazz 180 nm CMOS technology. The small pixel electrode allowed for the implementation of a fast, low noise and low power front-end, ...which is sensitive to the charge released by ionizing radiation in a 20–25 μm deep depleted region. The novel asynchronous matrix architecture is designed to ensure low power consumption and high rate capability. Such features make MALTA a possible candidate for the outer layer of ATLAS Inner Tracker (ITk) upgrade. Unirradiated and irradiated MALTA sensors have been extensively tested in laboratory and with high energy particle beams. Results of this measurements campaign are shown, and the further improvements that are being implemented in the next versions of the chip are discussed.
A 300 μm thick thin p-on-n silicon sensor was connected to an energy sensitive pixel readout ASIC and exposed to a beam of highly energetic charged particles. By exploiting the spectral information ...and the fine segmentation of the detector, we were able to measure the evolution of the transverse profile of the charge carriers cloud in the sensor as a function of the drift distance from the point of generation. The result does not rely on model assumptions or electric field calculations. The data are also used to validate numerical simulations and to predict the detector spectral response to an X-ray fluorescence spectrum for applications in X-ray imaging.
X-ray Transition radiation detectors (TRDs) are used for particle identification in both high energy physics and astroparticle physics. Particle identification is often achieved based on a threshold ...effect of the X-ray transition radiation (TR). In most of the detectors, TR emission starts at γ factors above ∼500 and reaches saturation at γ∼2−3⋅103. However, many experiments require particle identification up to γ∼105, which is difficult to achieve with current detectors, based only on the measurement of the photon energy together with the particle ionization losses. Additional information on the Lorentz factor can be extracted from the angular distribution of TR photons. TRDs based on pixel detectors give a unique opportunity for precise measurements of spectral and angular distributions of TR at the same time. A 500 μm thick silicon sensor bump bonded to a Timepix3 chip was used in a test beam measurement at the CERN SPS. A beam telescope was employed to separate clusters produced by the primary beam particles from the potential TR clusters. Spectral and angular distributions of TR were studied with high precision for the first time using beams of pions, electrons and muons at different momenta. In this paper, the measurement and analysis techniques are described, and first results are presented.
The last couple of years have seen the development of Depleted Monolithic Active Pixel Sensors (DMAPS) fabricated with a process modification to increase the radiation tolerance. Two large scale ...prototypes, Monopix with a column drain synchronous readout, and MALTA with a novel asynchronous architecture, have been fully tested and characterized both in the laboratory and in test beams. This showed that certain aspects have to be improved such as charge collection after irradiation and the output data rate. Some improvements resulting from extensive TCAD simulations were verified on a small test chip, Mini-MALTA. A detailed cluster analysis, using data from laboratory and test beam studies, at different biases, for high and low thresholds and before and after irradiation is presented, followed by detailed simulations showing that the digital architecture for both chips is capable of dealing with data rates of around 80 MHz/cm2 similar to what it is expected in the outer layer of the ATLAS inner tracker upgrade for the HL-LHC. The data rate capability and output bandwidth are studied using realistic hits generated by the ATLAS detector simulation framework.
Detector prototypes are commonly characterised in testbeams, either using charged particles or X-rays. Charged particles are used to quantify detector performance in terms of absolute efficiency, ...while X-rays can provide additional information about the detector structure. This paper presents an alternative approach to calculating charged particle efficiencies, using the results of an X-ray testbeam of the mini-MALTA CMOS prototype at Diamond Light Source, and additional laboratory measurements. Results are presented for an unirradiated and an irradiated sample and compared to the results of charged particle testbeams at SPS and ELSA. The extrapolated efficiencies are in agreement with the measured values. Additionally, the extrapolated efficiency maps provide more insight about the location of the pixel inefficiencies, due to the better spatial resolution of the X-ray testbeam.
This paper outlines the results of investigations into the effects of radiation damage in the mini-MALTA depleted monolithic pixel sensor prototype. Measurements were carried out at Diamond Light ...Source using a micro-focus X-ray beam, which scanned across the surface of the device in 2 μm steps. This allowed the in-pixel photon response to be measured directly with high statistics. Three pixel design variations were considered: one with the standard continuous n− layer layout and front-end, and extra deep p-well and n− gap designs with a modified front-end. Five chips were measured: one unirradiated, one neutron irradiated, and three proton irradiated. The standard design showed a decrease of 12% in pixel response after irradiation to 1e15 neq∕cm2. For the two new designs the pixel response did not decrease significantly after irradiation. A decrease of pixel response at high biasing voltages was observed. The charge sharing in the chip was quantified and found to be in agreement with expectations.
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