ALICE (A Large Ion Collider Experiment) is designed to address the physics of strongly interacting matter, and in particular the properties of the Quark-Gluon Plasma (QGP), using proton-proton, ...proton-nucleus and nucleus-nucleus collisions at the CERN LHC.
Quantum Chromo Dynamics (QCD) is well-established as the gauge theory of strong interactions. However, several of its fundamental aspects are not well-understood at present. There remain important ...open questions about the parton-hadron transition and the nature of confinement, and about the nature of QCD matter at high temperature. A much deeper insight into the mechanisms underlying chiral-symmetry breaking and the origin of light-quark mass is necessary.
The ALPIDE chip is a CMOS Monolithic Active Pixel Sensor being developed for the Upgrade of the ITS of the ALICE experiment at the CERN Large Hadron Collider. The ALPIDE chip is implemented with a ...180nm CMOS Imaging Process and fabricated on substrates with a high-resistivity epitaxial layer. It measures 15mm×30mm and contains a matrix of 512×1024pixels with in-pixel amplification, shaping, discrimination and multi-event buffering. The readout of the sensitive matrix is hit driven. There is no signaling activity over the matrix if there are no hits to read out and power consumption is proportional to the occupancy. The sensor meets the experimental requirements of detection efficiency above 99%, fake-hit probability below 10−5 and a spatial resolution of 5μm. The capability to read out Pb–Pb interactions at 100kHz is provided. The power density of the ALPIDE chip is projected to be less than 35mW/cm2 for the application in the Inner Barrel Layers and below 20mW/cm2 for the Outer Barrel Layers, where the occupancy is lower. This contribution describes the architecture and the main features of the final ALPIDE chip, planned for submission at the beginning of 2016. Early results from the experimental qualification of full scale prototype predecessors are also reported.
•The ALPIDE chip, an innovative CMOS pixel particle detector is described.•It achieves excellent detection performance figures and very low power consumption.•The characterization of prototypes confirms the achievement of the specifications.
A new 10m2 inner tracking system based on seven concentric layers of Monolithic Active Pixel Sensors will be installed in the ALICE experiment during the second long shutdown of LHC in 2019–2020. The ...monolithic pixel sensors will be fabricated in the 180nm CMOS Imaging Sensor process of TowerJazz. The ALPIDE design takes full advantage of a particular process feature, the deep p-well, which allows for full CMOS circuitry within the pixel matrix, while at the same time retaining the full charge collection efficiency. Together with the small feature size and the availability of six metal layers, this allowed a continuously active low-power front-end to be placed into each pixel and an in-matrix sparsification circuit to be used that sends only the addresses of hit pixels to the periphery. This approach led to a power consumption of less than 40mWcm−2, a spatial resolution of around 5μm, a peaking time of around 2μs, while being radiation hard to some 10131MeVneq/cm2, fulfilling or exceeding the ALICE requirements.
Over the last years of R & D, several prototype circuits have been used to verify radiation hardness, and to optimize pixel geometry and in-pixel front-end circuitry. The positive results led to a submission of full-scale (3cm×1.5cm) sensor prototypes in 2014. They are being characterized in a comprehensive campaign that also involves several irradiation and beam tests. A summary of the results obtained and prospects towards the final sensor to instrument the ALICE Inner Tracking System are given.
Abstract
A new forward calorimeter (FoCal), covering the pseudorapidity range 3.4 ≤
η
≤ 5.8, is proposed in order to extend the physics reach of ALICE during the LHC Run 4. The FoCal comprises a ...high-granularity electromagnetic calorimeter with silicon pixel and pad readout as well as a hadronic calorimeter. FoCal gives access to the nuclear gluon densities down to Bjorken-x ∼ 10
−6
, where they are not constrained by other measurements and their evolution may be affected by non-linear effects of quantum chromodynamics. The hadronic subsystem of FoCal (FoCal-H) will be based on capillary copper tubes with scintillating fibers inside. A full-length prototype was assembled and it was exposed to a non-separated charged particle beam in the H2 SPS CERN beamline in November 2022. An energy scan from 60 to 350 GeV was performed and the reconstructed signals are processed in a custom developed ROOT based environment. The design of the 2022 prototype as well as the first results from the energy reconstruction are presented.
Abstract The ITS3 upgrade baseline design employs MAPS (Monolithic Active Pixel Sensor) in bent state. Bending experiments with the existing ITS2 MAPS (=Alpide chip) show it remains functional but ...with relative large analog supply current changes. It is shown that by the piezoresistive effect, rotation of current mirror FETs can be responsible which was confirmed after validating the layout. Measured Gauge Factor has proper sign but is 3 times lower than typical values derived from literature. The magnitude of the measured strain induced PMOS V th shift is as expected but the sign differs for compressive strain with some of the literature.
Abstract The ALICE ITS3 is a novel vertex detector replacing the innermost layers of ITS2 during LS3. Composed of three truly cylindrical layers of wafer-sized 65 nm stitched Monolithic Active Pixel ...Sensors, ITS3 provides high-resolution tracking of charged particles generated in heavy-ion collisions. This contribution presents an overview of the ITS3 detector, highlighting its design features, integration and cooling, and the ongoing development towards the final sensor. Furthermore, the paper introduces the off-detector service electronics, which play an essential role in the readout, control, and power supply of the detector.
Abstract During the next Long Shutdown (LS3) of the LHC, planned for 2026, the innermost three layers of the ALICE Inner Tracking System will be replaced by a new vertex detector composed of curved ...ultra-thin monolithic silicon sensors. The R&D initiative on monolithic sensors of the CERN Experimental Physics Department, in cooperation with the ALICE ITS3 upgrade project, prepared the first submission of chip designs in the TPSCo 65 nm technology, called MLR1 (Multi Layer Reticle). It contains four different test structures with different process splits and pixel designs. These proceedings illustrate the first validation of the technology in terms of pixel performance and radiation hardness.
Abstract The Inner Tracking System (ITS) of the ALICE experiment at CERN will undergo an upgrade during the LHC long shutdown 3, in which the three innermost tracking layers will be replaced. This ...upgrade, named the Inner Tracking System 3 (ITS3), employs stitched wafer-scale Monolithic Active Pixel Sensors fabricated in a 65 nm CMOS process. The sensors are 260 mm in length and thinned to less than 50 μm then bent to form truly half-cylindrical half-barrels. The feasibility of this process for the ITS3 was explored with the first test production run (MLR1) in 2021, whose goal was to evaluate the charged particle detection efficiency and the sensor performance under non-ionising and ionising radiation up to the expected levels for ALICE ITS3 of 10 13 1 MeV n eq cm -2 (NIEL) and 10 kGy (TID). Three sensor flavours were produced to investigate this process: Analog Pixel Test Structure (APTS), Circuit Exploratoire 65 (CE65) and Digital Pixel Test Structure (DPTS). This contribution gives an overview of the MLR1 submission and test results, describing the different sensor flavours and presenting the results of the performance measurements done with particle beams for various chip variants and irradiation levels.
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