New Software-Based Readout Driver for the ATLAS Experiment

The High-Luminosity Large Hadron Collider (HL-LHC), scheduled to start operating in 2030, aims to increase the instantaneous luminosity by a factor of 10 compared to the LHC. To match this increase, the ATLAS experiment has been implementing a major upgrade program divided into two phases. The first phase (Phase-I), completed in 2022, introduced new trigger and detector systems that have been used during the Run 3 data taking period which began in July 2022. These systems have been used in conjunction with the new Data Acquisition (DAQ) Readout system, based on a software application called Software Readout Driver (SW ROD). SW ROD receives and aggregates data from the front-end electronics via the Front-End Link eXchange (FELIX) system and passes aggregated data fragments to the High-Level Trigger (HLT) system. During Run 3, SW ROD operates in parallel with the legacy Readout System (ROS) at an input rate of 100 kHz. For the Phase-II, the legacy ROS will be completely replaced with a new system based on the next generation of FELIX and an evolution of the SW ROD application called Data Handler. Data Handler has the same functional requirements as SW ROD but must be able to operate at an input rate of 1 MHz. To facilitate this evolution the SW ROD has been implemented using plugin architecture. This contribution presents the design and implementation of the SW ROD application for Run 3, along with the strategy for its evolution to the Phase-II Readout system. It discusses the lessons learned during Run 3 and describes the challenges that have been addressed to accomplish the demanding performance requirements of HL-LHC.

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.

The liquid argon calorimeters play a central role in the ATLAS experiment. The environment at the LHC collider imposes challenging tasks to their read-out system. To achieve measurements of particles and trigger signals at high precision, the detector signals are processed at various stages before reaching the data acquisition system (DAQ). Signals from the calorimeter cells are received by front-end boards, which digitize and sample the incoming pulse. Readout driver (ROD) boards further process the data at a trigger rate of up to 75 kHz. An optimal filtering procedure is applied to optimize the signal-to-noise ratio. The ROD boards calculate precise energy, time and quality of the detector pulse, which are then sent to the DAQ. In addition, the RODs perform a monitoring of the data. The architecture of the ATLAS liquid argon detector read-out is discussed, in particular the design and functionality of the ROD board. Performance results obtained with ROD prototypes as well as experience from complete test setups with final production boards are reported

The liquid argon calorimeters play a central role in the ATLAS (A Toroidal LHC Apparatus) experiment.The environment at the Large Hadron Collider (LHC)imposes strong constraints on the detectors readout systems.In order to achieve very high precision measurements,the detector signals are processed at various stages before reaching the Data Acquisition system (DAQ).Signals from the calorimeter cells are received by on-detector Front End Boards (FEB),which sample the incoming pulse every 25 ns and digitize itat a trigger rate of up to 75 kHz.Off-detector Read Out Driver (ROD)boards further process thedata and send reconstructed quantitiesto the DAQ while also monitoring the data quality.In this paper,the ATLAS Liquid Argon electronics chain is described first,followed by a detailed description of the off-detector readout system.Finally, the tests performed on the system are summarized.

The number of interactions per bunch crossing for the upgrade of the Large Hadron Collider is expected to be ten times greater than the actual one. As a consequence, the ATLAS detector for SLHC foresees the use of a larger number of readout channels and also a new trigger level is under development. In order to face with such issue, we developed a new architecture for the Read Out Driver (ROD) for the ATLAS RPC Muon Spectrometer in the barrel region. Presently, each ROD board receives ATLAS RPC Muon readout data and arranges all the data fragments of a sector of the spectrometer in a unique event, sending it to the next acquisition systems. Our new design is based on the new generation Xilinx Virtex5 FPGA and it works with a clock frequency six times greater than the actual bunch crossing rate of the LHC. We also implemented the output channel of the ROD, presently based on S-Link protocol, by using the GTP transceivers inside the FPGA. We present an overview of our design, focusing on the newly added hardware features.

ATLAS (A Toroidal LHC ApparatuS) is a general purpose experiment, which will start its operation at the Large Hadron Collider (LHC) at CERN in 2007. The ATLAS detector is designed to study the products of proton-proton collisions at c.m.s. energies of up to 14 TeV. Three Greek universities have taken the responsibility to construct 112 BIS-MDT (barrel inner small) chambers using 29000 drift tubes of /spl sim/1.7 m length that have been quality tested before assembly. This paper describes the quality assurance and quality control (QA/spl I.bar/QC) procedures for the monitored drift tubes (MDT), followed at the High Energy Physics Laboratory of the National Technical University of Athens. The quality parameters verification and the obtained results are presented.

The innermost part of the ATLAS (A Toroidal LHC Apparatus) experiment at the LHC (Large Hadron Collider), CERN (Conseil Eurpeenne pour la Recherche Nucleaire), will be a pixel detector, which is presently under construction. To operate the approx. 1700 detector modules and their related readout electronics a sophisticated power supply system is required. Its design constraints are the high power density and the sensitivity of the read out chips developed in deep sub-micron technology. A high granularity of the system is desired to allow individual adjustment and to minimize the number of elements out of service. We describe the layout of the full power supply system and concentrate on the components designed in-house: the supply system for the optical link, which offers the possibility of handling a high number of channels at a reasonable price and the remotely-programmable regulator stations, which protect the sensitive front end electronics.

Since the start of Large Hadron Collider (LHC) operation at √ s = 7 TeV in Spring 2010, the number of collisions produced has grown roughly exponentially with running time. By the end of the 2010 run, a sample of integrated luminosity around 45 pb had been collected, at a peak luminosity of around 10 cms. In addition, the first LHC run with lead ion collisions in November yielded approximately 9 μb at a nucleon-nucleon centre of mass energy of √ s = 2.76 TeV. The ATLAS detector [1] performed well throughout the 2010 run and its response was quickly understood. The results contained in this talk [2] are based on varying sample sizes taken from the 2010 data. LHC physics is an extremely fast-moving field. By the time of writing (May 2011), the 2011 data sample has already reached an integrated luminosity of over 250 pb, such that many of the results here will soon be superceded. For a complete current list of ATLAS publications and preliminary results, see [3].

Online track reconstruction is an important ingredient for the event selection at Large Hadron Collider (LHC) experiments. In the ATLAS experiment the first stage where this goal will be achievable is the software-based Second Level Trigger (LVL2). In this contribution we present an algorithm for fast pattern recognition and reconstruction of charged tracks and of the primary vertex in the framework of the High Level Trigger (HLT) of ATLAS. The pattern recognition makes extensive use of MC look-up-tables to quickly identify, in the innermost layers of the ATLAS silicon detectors, triplets of space points reconstructed from hits produced by the same track. The reconstruction strategy is compared, in the ATLAS LVL2 framework, with an alternative tracking algorithm, showing the complementarity of the two approaches. The algorithm's performance is presented for different event topologies and luminosities, showing good tracking capabilities and uniform results within mean execution times which are compatible with the LVL2 requirements.

The Phase-I upgrade of the trigger readout electronics for the ATLAS liquid argon (LAr) calorimeters will be installed during the second long shutdown of the Large Hadron Collider (LHC) in 2019-2020, which will enable enhanced instantaneous luminosities during LHC Run 3 from 2021 through 2023. In this trigger upgrade, the so-called supercells are introduced to provide higher granularity, higher resolution, and longitudinal shower shape information from the LAr calorimeters to the Level-1 trigger processors. A new LAr trigger digitizer board (LTDB) will process and digitize up to 320 channels of supercell signals and transmit them via 40 fiber optical links to the back-end where the data are further processed and transmitted to the trigger processors. Five pairs of bidirectional GigaBit Transceiver links are used for slow control and monitoring between LTDB and the front-end link eXchange (FELIX) in the ATLAS trigger and data acquisition (TDAQ) system. The LTDB also outputs 64 summed analog legacy signals to the current tower builder board via a new baseplane. A test system for the production of 124 LTDBs has been developed, supporting configuration and calibration of all application-specified integrated circuits (ASICs) on the LTDB, as well as evaluation of full LTDB functionality.

In this paper we present the performance of two algorithms currently running in the Tile Calorimeter Read-Out Driver boards for the commissioning of ATLAS. The first algorithm presented is the so called Optimal Filtering. It reconstructs the deposited energy in the Tile Calorimeter and the arrival time of the data. The second algorithm is the MTag which tags low transverse momentum muons that may escape the ATLAS muon spectrometer first level trigger.Comparisons between online (inside the Read-Out Drivers) and offline implementations are done with an agreement around 99% for the reconstruction of the amplitude using the Optimal Filtering algorithm and a coincidende of 93% between the offline and online tagged muons for the MTag algorithm. The processing time is measured for both algorithms running together with a resulting time of 59.2 μs which, although above the 10 μs of the first level trigger, it fulfills the requirements of the commissioning trigger ( ∼ 1 Hz). We expect further optimizations of the algorithms which will reduce their processing time below 10 μs.

The ATLAS experiment at CERN has planned many upgrades, in order to cope with the instantaneous luminosity that will be delivered by the Large Hadron Collider (LHC) machine in the next decade. These upgrades will allow the ATLAS experiment to keep or improve its current performance for Run 3, expected to start in 2021, and for the High Luminosity LHC program (HL-LHC) expected to start in ∼2027. For Run 3, we expect an instantaneous luminosity of 2-3 × 1034 cm−2 s−1 and an average pileup of ~80 collisions/bunch crossing, while for the HL-LHC phase, an instantaneous luminosity of 7.5 × 1034 cm−2 s−1 and an average pileup of ~200 collisions/bunch crossing are foreseen. Although the upgrades are essential to achieve the physics goals, they represent a huge challenge for the detector, trigger and data acquisition (TDAQ) systems. The status of the upgrade activities is presented.

The standard model of particle physics1–4 describes the known fundamental particles and forces that make up our Universe, with the exception of gravity. One of the central features of the standard model is a field that permeates all of space and interacts with fundamental particles5–9. The quantum excitation of this field, known as the Higgs field, manifests itself as the Higgs boson, the only fundamental particle with no spin. In 2012, a particle with properties consistent with the Higgs boson of the standard model was observed by the ATLAS and CMS experiments at the Large Hadron Collider at CERN10,11. Since then, more than 30 times as many Higgs bosons have been recorded by the ATLAS experiment, enabling much more precise measurements and new tests of the theory. Here, on the basis of this larger dataset, we combine an unprecedented number of production and decay processes of the Higgs boson to scrutinize its interactions with elementary particles. Interactions with gluons, photons, and W and Z bosons—the carriers of the strong, electromagnetic and weak forces—are studied in detail. Interactions with three third-generation matter particles (bottom (b) and top (t) quarks, and tau leptons (τ)) are well measured and indications of interactions with a second-generation particle (muons, μ) are emerging. These tests reveal that the Higgs boson discovered ten years ago is remarkably consistent with the predictions of the theory and provide stringent constraints on many models of new phenomena beyond the standard model.

The commissioning of the hadronic Tile Calorimeter (TileCal) of the ATLAS experiment was largely complete and the detector fully operational before the LHC first beam on 10 September 2008. During the installation phase of the experiment, a large number of online tools have been developed in order to test the correct functionality of the hardware. These tools were specifically designed for TileCal from the DVS (Diagnostic and Verification System) of the ATLAS TDAQ software. At the same time, Read-Out software packages were designed and tested to satisfy LHC requirements in particular for high rate data acquisition. In parallel, the commissioning of the slow control system which controls and monitors such things as the low voltage and the high voltage, as well as infrastructure and safety, was ongoing. The large number of channels (almost 10000) and the complexity of the detector require the development of advanced tools for calibrating and validating the online and offline reconstruction. A set of monitoring tools has been also developed in order to certify the various stages of data flow from the detector front-end to the Read-Out Drivers (RODs) and the Read-Out System (ROS) and finally the reconstructed parameters. Additional tools based on the slow read-out system (Integrator read-out) have been developed in order to monitor photo-tube mean currents and provide luminosity and beam condition information. The TileCal detector has been fully integrated with the other subsystems and is intensively involved since the beginning in the commissioning phase with cosmic ray events. Many calibration and performance studies were done using these cosmic data in order to validate the energy reconstruction, the timing, energy loss of muons, etc.

Recent results on studies of hard scattering processes and jet quenching in nuclear collisions from the ATLAS and CMS experiments at the Large Hadron Collider (LHC) are reviewed. They are based on high statistics samples of PbPb collisions at √ sNN = 2.76 TeV collected at the LHC in 2011, and pp collisions at √ s = 2.76 TeV and pPb collisions at √ sNN = 5.02 TeV collected in 2013. New results for the jet nuclear modification factor, RAA, confirm a strong suppression of jet production. Modifications of jet fragmentation properties in PbPb collisions, are observed. In pPb collisions jets are not strongly modified, but some non-scaling behavior of jet rates in collisions with different centralities is observed by ATLAS. New measurements for the electroweak boson production in pPb collisions allow a more precise testing of parton distributions in lead nuclei with the conclusion that the EPS09 description of nuclear modifications of parton distribution functions is preferred.