Prototype ATLAS IBL modules using the FE-I4A front-end readout chip

Silicon Sensor Technologies for the ATLAS IBL Upgrade

During Run 1 of the Large Hadron Collider (LHC), the ATLAS Pixel Detector has shown excellent performance. The ATLAS collaboration took advantage of the first long shutdown of the LHC during 2013 and 2014 and extracted the ATLAS Pixel Detector from the experiment, brought it to surface and maintained the services. This included the installation of new service quarter panels, the repair of cables, and the installation of the new Diamond Beam Monitor (DBM). Additionally, a completely new innermost pixel detector layer, the Insertable B-Layer (IBL), was constructed and installed in May 2014 between a new smaller beam pipe and the existing Pixel Detector. With a radius of 3.3cm the IBL is located extremely close to the interaction point. Therefore, a new readout chip and two new sensor technologies (planar and 3D) are used in the IBL. In order to achieve best possible physics performance the material budget was improved with respect to the existing Pixel Detector. This is realized using lightweight staves for mechanical support and a CO2 based cooling system.This paper describes the improvements achieved during the maintenance of the existing Pixel Detector as well as the performance of the IBL during the construction and commissioning phase. Additionally, first results obtained during the LHC Run 2 demonstrating the distinguished tracking performance of the new Four Layer ATLAS Pixel Detector are presented.

The upgrade for ATLAS detector will undergo different phase towards super-LHC. The first upgrade for the Pixel detector will consist of the construction of a new pixel layer which will be installed during the first shutdown of the LHC machine (LHC phase-I upgrade). The new detector, called Insertable B-Layer (IBL), will be inserted between the existing pixel detector and a new (smaller radius) beam-pipe at a radius of 3.3 cm. The IBL will require the development of several new technologies to cope with increase of radiation or pixel occupancy and also to improve the physics performance which will be achieved by reducing the pixel size and of the material budget. Three different promising sensor technologies (planar-Si, 3D-Si and diamond) are currently under investigation for the pixel detector. An overview of the project with particular emphasis on pixel module is presented in this paper.

Test beam results of irradiated modules for the CMS Phase-2 upgrade equipped with HPK planar pixel sensors and RD53B-CMS readout chips

During the first LHC long shutdown (2013/14) a new innermost pixel layer will be added to the present ATLAS Pixel Detector. The Insertable B-Layer (IBL) is a high-reliability, ultra light and radiation hard Pixel Detector assembled with 3D n-in-p and planar n-in-n pixel sensors. Facing the effects of increased luminosity and radiation damage, IBL is expected to improve the b-tagging efficiency, help with pattern recognition performance and add tracking precision with respect to the current detector. Single and double chip modules are loaded on local mechanical support, in the form of 14 staves arranged in cylindrical barrel around the beam pipe. The production of the modules has already started, aiming for a total production of 24 staves including spares. Systematic Quality Assurance (QA) and Quality Control (QC) plans concerning modules, staves and flex from production to final assembly have been put in place. QA is performed in several collaborating institutes and final validation before installation in the ATLAS experiment will be carried out at CERN. Dedicated set-ups have been constructed in order to perform the full chain of QAlQC tests on the production staves. A CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> cooling system is used to cool the pixel modules down to -35°C and an electronic chain similar to the final one has been developed. Furthermore a linear motion system carrying two 241 Am sources with an activity of 41 MBq each is mounted over the stave in order to perform a final characterization of the sensor's performance. The realization of source scans on the 24 production staves permits to analyze the response of sensors to radiation, to easily identify dead pixels, and to provide data for an eventual re-calibration of the charge calibration. The setup and first results obtained on prototype staves are described in detail.

Development of Edgeless Silicon Pixel Sensors on p-type substrate for the ATLAS High-Luminosity Upgrade

Various structures for n-in-p planar pixel sensors have been developed at KEK in order to cope with the huge particle fluence in the upcoming LHC upgrades. Performances of the sensors with different structures have been evaluated with testbeam. The n-in-p devices were connected by bump-bonding to the ATLAS Pixel front-end chip (FE-I4A) and characterized before and after the irradiation to 1×1016 1MeV neq/cm2. Results of measurements with 120GeV/c momentum pion beam at the CERN Super Proton Synchrotron (SPS) in September 2012 are presented.

The ATLAS Insertable B-Layer (IBL) is the innermost layer of pixel detectors, and was installed in May 2014 at a radius of 3.3 cm from the beam axis, between the existing Pixel detector and a new smaller radius beam-pipe. The new detector, built to cope with high radiation and occupancy, is the first large scale application of 3D sensors and CMOS 130 nm technology. The IBL detector construction was completed within about two years (2012 – 2014), and the key features and challenges met during the IBL project are presented, as well as its commissioning and operational experience at the LHC.

The High Luminosity upgrade of the CERN Large Hadron Collider (HL-LHC) requires new high-radiation tolerant silicon pixel sensors for the innermost part of the tracking detector in the CMS experiment. The innermost layer of the tracker, which is as close as 3 cm from the interaction point, will be exposed to a fluence of3.4× 1016 neqcm-2 during the high-luminosity operation period. The 3D pixel sensor technology has been proven to be the best option for such a layer in terms of radiation tolerance and low power consumption. An extensive program aiming at 3D pixel sensors has been carried out in the context of the CMS tracker R&D activities. The sensors have been produced by Fondazione Bruno Kessler (Trento, Italy) and Centro Nacional de Microelectrónica (Barcelona, Spain). They are connected with the CROCv1 readout chip, which is a prototype of the final version. The modules have been tested in beams at CERN and DESY, before and after irradiation up to an equivalent fluence of about1.6 × 1016 neqcm-2. An overview of the results obtained in the latest beam test experiments is presented, including hit detection efficiency and spatial resolution. The analysis of collected data shows excellent performance, with around 98% hit detection efficiencies measured after irradiation.

The phase 1 upgrade of the ATLAS [1] pixel detector will be done by inserting a fourth pixel layer together with a new beampipe into the recent three layer detector. This new detector, the Insertable B-Layer (IBL) should be integrated into the recent pixel system with as few changes in services as possible, but deliver some advantages over the recent system. One of those advantages will be a new data transmission link from the detector modules to the off-detector electronics, requiring a re-design of the electro-optical converters on the off-detector side. First ideas of how to implement those, together with some ideas to reduce cost by increasing the systems throughput are discussed.

Achievements of the ATLAS upgrade planar pixel sensors R&D project

An upgrade program is underway to increase the luminosity of the LHC up to about 7.5×1034 cm−2s−1 in 2027, with the goal of an integrated luminosity of 3000 fb−1 by the end of 2037. This High Luminosity scenario, HL-LHC, presents new challenges of higher data rates and increased radiation hardness for the pixel detector: a non-ionizing fluence of 2.3×1016 neq/cm2 an ionizing dose of 12 MGy, is expected on the inner pixel layer for 3000 fb−1 integrated luminosity. To maintain or even improve the performance of the present system, new technologies have to be fully exploited for the so-called Phase-II upgrade. Among them is the future version of front-end chips in 65-nm CMOS by the CERN RD53 Collaboration which supports small pixel sizes of 50×50 or 25×100 μm2 lower thresholds (∼ 1000 e−). For the development of the appropriate planar pixel sensor, CMS has recently launched a submission of n+-p sensors on 6 inch wafers with an active thickness of 150 μm at Hamamatsu. The submission consists of physically thinned, directly bonded and deep diffused wafers with p-stop or p-spray isolation. A variety of sensors with and without biasing scheme is designed to match the different read-out chips (RD53A, ROC4Sens, etc.) and first hybrid modules are assembled at Fraunhofer IZM. In this document, we will present an overview of the Phase II pixel R&D program and report on preliminary results on the HPK submission.

Optical link ASICs for LHC upgrades

We report on the design and TCAD simulations of planar active-edge pixel sensors within the INFN PixFEL project. These devices are intended as one of the building blocks for the assembly of a multilayer, four-side buttable tile for X-ray imaging applications in future Free Electron Laser facilities. The requirements in terms of very wide dynamic range and tolerance to extremely high ionizing radiation doses call for high operation voltages. A comprehensive TCAD simulation study is presented, aimed at the best trade-offs between the minimization of the edge region size and the sensor breakdown voltage.

The High Luminosity LHC upgrade demands enhanced tracking, prompting a complete replacement of ATLAS's Inner Detector with the all-silicon Inner Tracker (ITk). Spanning 33–291 mm from the beam pipe, ITk will use hybrid pixel detectors with 65 nm CMOS chips. The inner region, facing extreme radiation, will feature 3D pixel sensors due to their superior radiation tolerance, while the outer regions will use planar sensors. The production of 3D sensors is distributed among two vendors, FBK and SINTEF. The ITk linear triplet module consists of three hybrids (readout chip bump-bonded to a 3D pixel sensor) mounted on a flexible PCB. Extensive testing has been carried out on a linear triplet module in 2025 at CERN's test beam facilities, using 120 GeV pion beams to validate its performance under HL-LHC conditions. The most recent results of the module studied after irradiation will be presented here.