Level Trigger Research Articles

Upgrade of the ATLAS muon system for the HL-LHC

Abstract The muon spectrometer of the ATLAS detector will be significantly upgraded during the Phase-II upgrade in Long Shutdown 3 in order to cope with the operational conditions at the High-Luminosity LHC in Run 4 and beyond. Most of the electronics for the Resistive Plate Chambers (RPC), Thin Gap Chambers (TGC), and Monitored Drift Tube (MDT) chambers will be replaced to make them compatible with the higher trigger rates and longer latencies necessary for the new level-0 trigger. The MDT chambers will be integrated into the level-0 trigger in order to sharpen the momentum threshold. Additional RPC chambers will be installed in the inner barrel layer to increase the acceptance and robustness of the trigger. Some of the MDT chambers in the inner barrel layer will be replaced with new small-diameter MDTs. New TGC triplet chambers in the barrel–endcap transition region will replace the current TGC doublets to suppress the high trigger rate from random coincidences in this region. The power system for the RPC, TGC, and MDT chambers and electronics will need to be replaced due to component obsolescence, aging, and radiation damage. A high- η tagger is under consideration to extend the angular acceptance for muon identification. The Phase-II upgrade concludes the process of adapting the muon spectrometer to the ever increasing performance of the LHC, which started with the Phase-I upgrade New Small Wheel project that will replace the Cathode Strip Chambers and the MDT chambers of the innermost endcap wheels by Micromegas and small-strip TGCs.

Background Suppression with the Belle II Neural Network Trigger

Neural networks are going to be used in the pipelined first level trigger of the upgraded flavor physics experiment Belle II at the high luminosity B factory SuperKEKB in Tsukuba, Japan. An instantaneous luminosity of L = 8 × 1035cm−2s−1 is anticipated, 40 times larger than the world record reached with the predecessor KEKB. Background tracks, with vertices displaced along the beamline (z-axis), are expected to be severely increased due to the high luminosity. Using input from the central drift chamber, the main tracking device of Belle II, the online neural network trigger provides 3D track reconstruction within the fixed latency of the first level trigger. In particular, the robust estimation of the z-vertices allows a significantly improved suppression of the machine background. Based on a Monte Carlo background simulation, the high event rate faced by the first level trigger is analyzed and the benefits of the neural network trigger are evaluated.

Real-time heterogeneous stream processing with NaNet in the NA62 experiment

The use of GPUs to implement general purpose computational tasks, known as GPGPU since fifteen years ago, has reached maturity. Applications take advantage of the parallel architectures of these devices in many different domains.Over the last few years several works have demonstrated the effectiveness of the integration of GPU-based systems in the high level trigger of various HEP experiments. On the other hand, the use of GPUs in the DAQ and low level trigger systems, characterized by stringent real-time constraints, poses several challenges.In order to achieve such a goal we devised NaNet, a FPGA-based PCI-Express Network Interface Card design capable of direct (zero-copy) data transferring with CPU and GPU (GPUDirect) while online processing incoming and outgoing data streams. The board provides as well support for multiple link technologies (1/10/40GbE and custom ones).The validity of our approach has been tested in the context of the NA62 CERN experiment, harvesting the computing power of last generation NVIDIA Pascal GPUs and of the FPGA hosted by NaNet to build in real-time refined physics-related primitives for the RICH detector (i.e. the Cerenkov rings parameters) that enable the building of more stringent conditions for data selection in the low level trigger.

Deposition in a changing paleogulf: evidence from the Pliocene–Quaternary sedimentary succession of the Nile Delta, Egypt

Sedimentary complexes of ancient gulfs provide valuable information about paleoenvironmental dynamics. The study of several Pliocene–Pleistocene sections allowed reconstruction of the regional stratigraphical framework in the southwestern fringes of the Nile Delta. The Kafr El-Shiekh, the Gar El-Muluk, and the Kom El-Shelul formations of the Zanclean Age and the Wastani Formation of the Piacenzian Age constitute the Pliocene sedimentary succession in the study area. The establishment of 11 facies types related to 5 facies associations coupled with the results of the stratigraphical study indicate the existence of a paleogulf corresponding to the modern delta and lower valley of the Nile. This Nile Paleogulf appeared and reached its maximum spatial extent in the beginning of the Pliocene. Then, it retreated gradually and disappeared before the end of this epoch when alluvial sedimentation reestablished. There was significant flux of siliciclastic material to the study area. The Zanclean Flood in the Mediterranean Sea allowed marine incursion in the study area where the river valley incised during the precedent Messinian Salinity Crisis. Regional tectonic uplift and filling of the accommodation space with siliciclastic material from the eroded land were the main controls on the paleogulf evolution. Strengthened glaciation triggered global sea level fall, and alluvial deposition dominated the study area in the late Pliocene–Pleistocene.

Boosted Decision Trees in the Level-1 Muon Endcap Trigger at CMS

The first implementation of a Machine Learning Algorithm inside a Level-1 trigger system at the LHC is presented. The Endcap Muon Track Finder (EMTF) at CMS uses Boosted Decision Trees (BDTs) to infer the momentum of muons in the forward region of the detector, based on 25 different variables. Combinations of these variables representing 230 distinct patterns are evaluated offline using regression BDTs. The predictions for the 230 input variable combinations are stored in a 1.2 GB look-up table in the EMTF hardware. The BDTs take advantage of complex correlations between variables, the inhomogeneous magnetic field, and non-linear effects – like inelastic scattering – to distinguish high momentum signal muons from the overwhelming low-momentum background. The new momentum algorithm reduced the background rate by a factor of three with respect to the previous analytic algorithm, with further improvements foreseen in the coming year.

The ATLAS Electron and Photon Triggers

Electron and photon triggers covering transverse energies from 5 GeV to several TeV are essential for signal selection in a wide variety of ATLAS physics analyses to study Standard Model processes and to search for new phenomena. The ATLAS trigger system is divided in a hardware-based Level-1 trigger and a software-based high-level trigger, both of which were upgraded during the LHC shutdown in preparation for Run 2 operation. To cope with the increasing luminosity and more challenging pile-up conditions at a centre-of-mass energy of 13 TeV, the trigger selections at each level are optimised to control the rates and keep efficiencies high. To achieve this goal multivariate analysis techniques are used. The ATLAS electron and photon triggers and their performance with Run 2 data are presented.

Multi-threading in the ATLAS High-Level Trigger

Over the next decade of LHC operation the instantaneous luminosity will reach up 7.5 times the design value with over 200 interactions per bunch-crossing. This will pose unprecedented challenges for the ATLAS trigger system.We report on a prototype of the High Level Trigger software that maximizes commonality with offline reconstruction software while retaining the key aspects of trigger functionality including regional reconstruction and early event rejection. We report on the first experience of migrating trigger algorithms to this new framework and present the next steps towards a full implementation of the ATLAS trigger within AthenaMT.

Evaluation of Demand Response on System Reliability and Cable Aging

Emergency loading implementation brings reliability and flexibility benefits to the operator. However, its application results in higher cable temperature, which may lead to increase of aging risk. Furthermore, demand response (DR) option can clip the customer loads and shift them to a different period. The DR clipping process reduces the loading of the network to avoid cable overheating and reduce its aging risk. The study aims to evaluate the impact of DR in increasing the reliability of the system as well as reducing the aging of the network. The proposed DR is implemented in the cable-based transmission network, as a complementary of emergency loading, by taking into account the large thermal inertia of the cable. It uses cable temperature elevation as the trigger as an alternative to demand level trigger, which is the traditional approach. The evaluation uses Sequential Monte Carlo Simulation (SMCS) on the IEEE 14 Bus Reliability Test System. The implementation of temperature-based DR reduces the network aging by 3% as well as expected energy not supplied by 34% compared to the emergency loading only.

Search for narrow and broad dijet resonances in proton-proton collisions at sqrt{s}=13 TeV and constraints on dark matter mediators and other new particles

Searches for resonances decaying into pairs of jets are performed using proton-proton collision data collected at sqrt{s}=13 TeV corresponding to an integrated luminosity of up to 36 fb−1. A low-mass search, for resonances with masses between 0.6 and 1.6 TeV, is performed based on events with dijets reconstructed at the trigger level from calorimeter information. A high-mass search, for resonances with masses above 1.6 TeV, is performed using dijets reconstructed offline with a particle-flow algorithm. The dijet mass spectrum is well described by a smooth parameterization and no evidence for the production of new particles is observed. Upper limits at 95% confidence level are reported on the production cross section for narrow resonances with masses above 0.6 TeV. In the context of specific models, the limits exclude string resonances with masses below 7.7 TeV, scalar diquarks below 7.2 TeV, axigluons and colorons below 6.1 TeV, excited quarks below 6.0 TeV, color-octet scalars below 3.4 TeV, W′ bosons below 3.3 TeV, Z′ bosons below 2.7 TeV, Randall-Sundrum gravitons below 1.8 TeV and in the range 1.9 to 2.5 TeV, and dark matter mediators below 2.6 TeV. The limits on both vector and axial-vector mediators, in a simplified model of interactions between quarks and dark matter particles, are presented as functions of dark matter particle mass and coupling to quarks. Searches are also presented for broad resonances, including for the first time spin-1 resonances with intrinsic widths as large as 30% of the resonance mass. The broad resonance search improves and extends the exclusions of a dark matter mediator to larger values of its mass and coupling to quarks.

Protecting Museum Collections from Vibrations Due to Construction: Vibration Statistics, Limits, Flexibility and Cooperation

ABSTRACT Vibrations due to heavy construction work continue to be a major concern for museums. Although there has been an increase in research on the effect of vibrations on objects of cultural heritage in recent years, selecting measures to protect collections and remain open during construction work continues to be difficult because of a lack of data on what objects can actually withstand, the complexity of vibration loads, and the uniqueness of each situation. The major renovation of the Central Library in Liverpool, UK, which shared walls with the World Museum and Walker Art Gallery, both of which belong within National Museums Liverpool, showed how museums and other institutions can successfully deal with such situations. An integral approach was taken, beginning with an extensive risk analysis to determine which objects could remain on display, which needed extra protection and regular condition monitoring, and which had to be removed. The museums then negotiated a vibration protocol and action plan with the contractors, including continuous monitoring, and trigger levels requiring consultation or work stoppage. Vibration data were also stored and used for later analysis. This integral approach was successful in protecting the collections on exhibition, with only two incidents of reported damage directly related to vibrations. A combination of museum staff experience, excellent communications with the contractors, and some flexibility in defining vibration limits provided a successful recipe for both museums. The analysis of the vibration data using the basic engineering concept of the Palmgren-Miner rule, supports a more flexible approach to setting vibration limits based on recently published guidelines.

A multi-channel PCI express readout board for fast readout of large pixel detectors

Recently the ATLAS Pixel Detector at CERN has been upgraded by inserting an additional layer of pixels, the Insertable B-Layer (IBL). In addition, the off-detector readout electronics of the other layers that composed the Pixel Detector (the B-Layer, the Layer 1, the Layer 2 and the Disks) were updated using the IBL readout boards. The system has been updated, one layer at a time, giving priority to the next critical layer as the luminosity and level-1 trigger frequency increased. Hence, after IBL, the first critical layer was the Layer 2, then the Layer 1 and finally the B-Layer and the Disks. Eventually, after the technical stop in 2018 the entire ATLAS Pixel Detector will share the same off-detector readout electronics.In parallel with the commissioning of the upgrade of the current ATLAS Pixel Detector we have designed and fabricated a new readout electronic board to address the requirements of the LHC Phase-2 upgrade. Two batches of prototypes of a Peripheral Component Interconnect Express (PCIe) Gen. 2 boards have been designed and fabricated, the second being a patched version of the first. The first batch was composed of two boards, called Pixel ReadOut Driver (Pixel_ROD) and the second batch was made of five cards called π-LUP. All the boards feature many of the input–output ports and interfaces to address the requirements of the future front-end electronics being developed for the Large Hadron Collider (LHC) Phase-2 upgrade. Thus, the current VERSABUS Module Eurocard (VME) bus will be replaced with the PCIe bus to accommodate the huge increase of throughput (data to be transferred to the DAQ). In this new scenario, the GigaBit Transceiver (GBT) and Aurora protocols are compatible with our boards and the GBTx and RD53A chips will be the first components to be interfaced with. Some laboratory results and measurements are presented here.

The implementation of Global Feature EXtractor (gFEX) - the ATLAS Calorimeter Level 1 Trigger system for LHC Run-3 upgrade

As part of the ATLAS Phase-I Upgrade, the global Feature EXtractor (gFEX) is one of several hardware modules designed to help maintain the ATLAS Level-1 trigger acceptance rate with the increasing Large Hadron Collider (LHC) luminosity and the increasing Pile-Up conditions. The gFEX is used to identify patterns of energy associated with the hadronic decays of high momentum Higgs, W & Z bosons, top quarks, and exotic particles in real time at the 40 MHz LHC bunch crossing rate. The board is required to receive coarse-granularity (Δη×Δφ = 0.2×0.2 gTower) information from the entire ATLAS calorimeters on 276 optical fibers. A prototype v1 with one Xilinx ZYNQ FPGA, and one Vertex-7 FPGA for technology validation has been designed and tested in 2015. With the lessons learned from the prototype v1, a prototype v2 with three Vertex UltraScale FPGAs and one ZYNQ FPGA has been implemented to verify full functionalities of gFEX in 2016. Based on the prototype v2 design, a prototype v3, the final gFEX prototype, is implemented, which is an ATCA module consisting of three Vertex UltraScale+ FPGAs, one ZYNQ UltraScale+ SoC, and 35 MiniPODs. This board receives up to 300 fiber optical links from calorimeters and transmits trigger data on 96 links to the to the ATLAS Level-1 Topological trigger (L1Topo [1]) at the speed up to 12.8 Gb/s. There are also 24 electrical links on board for communication between two FPGAs with the speed up to 25.6 Gb/s. The performance of three prototype boards have been tested and evaluated. For the prototype v3 board, the high-speed optical links are stable at 12.8 Gb/s with Bit Error Ratio (BER) < 1 × 10-15. The low-latency parallel GPIO (General Purpose I/O) buses between FPGAs are stable at 1.12 Gb/s. The peripheral components of ZYNQ UltraScale+ SoC, such as 16 GB DDR4 DIMM, UART, SPI flashes, and Ethernet, have also been verified. The test results of the prototype v3 board validate the gFEX technologies, architecture and full functionalities. Now the final production board is being produced.

FELIX: the New Detector Interface for the ATLAS Experiment

During the next major shutdown (2019-2020), the ATLAS experiment at the LHC will adopt the Front-End Link eXchange (FELIX) system as the interface between the data acquisition, detector control and TTC (Timing, Trigger and Control) systems and new or updated trigger and detector front-end electronics. FELIX will function as a router between custom serial links from front-end ASICs and FPGAs to data collection and processing components via a commodity switched network. Links may aggregate many slower links or be a single high bandwidth link. FELIX will also forward the LHC bunch-crossing clock, fixed latency trigger accepts and resets received from the TTC system to front-end electronics. The FELIX system uses commodity server technology in combination with FPGA-based PCIe I/O cards. The FELIX servers will run a software routing platform serving data to network clients. Commodity servers connected to FELIX systems via the same network will run the new Software Readout Driver (SW ROD) infrastructure for event fragment building and buffering, with support for detector or trigger specific data processing, and will serve the data upon request to the ATLAS High Level Trigger for Event Building and Selection. This paper will cover the design and status of FELIX, the SW ROD, results of early performance testing and integration tests with several ATLAS front-ends.

Design and Evaluation of the LAr Trigger Digitizer Board in the ATLAS Phase-I Upgrade

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.

Effect of Cardiogenic Oscillations on Trigger Delay During Pressure Support Ventilation.

Sensitive flow or pressure triggers are usually applied to improve ventilator response time. Conversely, too sensitive triggers can incur risk of auto-triggering, a type of asynchrony in which a breath is triggered without inspiratory muscle activity. A frequent cause of auto-triggering is cardiogenic oscillations, characterized by cyclical variations in pressure and flow waveforms caused by cardiac contractions. Our goal was to test trigger performance and capacity to abolish auto-triggering in 5 different ICU ventilators using different simulated levels of cardiogenic oscillations. A mechanical breathing simulator was used to test 5 different ICU ventilators' trigger response time and capacity to minimize auto-triggering in conditions with 0, 0.25, 0.5, and 1 cm H2O cardiogenic oscillation. Each ventilator was evaluated until an ideal trigger was found (the most sensitive that abolished auto-triggering). When the least sensitive flow trigger was unable to avoid auto-triggering, a pressure trigger was used. We compared time delay, airway pressure drop until triggering, and work of breathing before each trigger, all at the ideal trigger level for each cardiogenic oscillation amplitude. We also assessed the proportion of auto-triggered breaths in the whole range of trigger levels tested. Larger cardiogenic oscillations were associated with more frequent auto-triggering. To avoid auto-triggering, less sensitive triggers were required (+2.51 L/min per 1 cm H2O increase in cardiogenic oscillation; 95% CI 2.26-2.76, P < .001). Time delay increased with larger cardiogenic oscillations, because less sensitive trigger levels were required to abolish auto-triggering (4.79-ms increase per 1 L/min increment on flow trigger). More sensitive triggers led to faster ventilator response, but also to more frequent auto-triggering. To avoid auto-triggering, less sensitive triggers were required, with consequent slower trigger response. To compare trigger performance in a scenario that more closely represents clinical practice, evaluation of the tradeoff between time delay and frequency of auto-triggering should be considered.

Partial discharge detection on 320 kV VSC-HVDC XLPE cable with artificial defects under DC voltage

VSC-HVDC power transmission systems based on extruded cables are being commissioned with higher rated voltages and longer distances in recent years. In China, the rated voltage of commissioned VSC-HVDC cable projects has been increased from 160 to 200 kV, and then to 320 kV in the past 5 years. To investigate the feasibility of discovering insulation defects of an XLPE HVDC cable system using partial discharge detection under DC voltage, a test cable loop was built using the same batch of 320 kV HVDC XLPE cable used to construct the Xiamen ± 320 kV VSC-HVDC project. Artificial defects of insulation wound and semi-conductive layer tips were designed and constructed at the joint. The two types of defects were effectively detected by the HVDC partial discharge test, and the measured results show distinguished discharge characteristics. Suggestions for determining trigger level and partial discharge inception voltage under DC voltage for partial discharge detection of extruded HVDC cables are given.

Trigger Study on the AMoRE-Pilot Detector

We present a systematic trigger study for the Advanced Molybdenum-based Rare process Experiment (AMoRE), an international project searching for the neutrinoless double beta decay ( $$0\nu \beta \beta $$ ) of $$^{100}\hbox {Mo}$$ . AMoRE utilizes a heat and light detection method at millikelvin temperatures. A detector module of AMoRE is composed of a large crystal absorber and metallic magnetic calorimeter temperature sensors. We applied a software filter with various conditions to the continuously saved data from the current AMoRE setup. With a trigger level set to 5 times the standard deviation of the noise signals resulting from a Butterworth filter, an energy threshold, defined as the energy of the signals leading to a 50% trigger efficiency, was found to be 2.2 keV.

T77. Reference values for jitter recordings with concentric needle electrodes on stimulated frontalis

Single fiber electromyography (SFEMG) serves as the most sensitive technique to assess neuromuscular transmission (NMT). In recent years, disposable concentric needle electrodes (CNE) become an alternative to single fiber electrodes for recordings because of concerns about the risk of transmitting infections. Reference values for this new method should be established first before its clinical use in differential diagnosis of neuromuscular junction disorders. We recruited 73 patients, 32 males and 41 females (18–83 years, mean age 52.2 ± 14.0 years), with eyelid, ocular, or weakness symptoms other than myasthenia gravis (MG). None of them had neuromuscular junction diseases, facial nerve palsy or myopathies. The facial nerve was stimulated at the temporal branch with surface electrodes. CNE recorded 20 apparent single fiber action potentials (ASFAPs) from the frontalis for each subjects. Jitter was measured with amplitude level trigger method and expressed as the mean consecutive difference (MCD). The mean MCD were 17.68 ± 3.30 μs for subjects and 17.66 ± 7.81 μs for individual potentials. For ensuring higher specificity, we set the mean values plus 3 SD as the upper normal limits, and figured out the corresponding cut-offs of 28 μs for mean jitter values and 42 μs for jitter values of individual potentials. Our data derived from disease control subjects are similar to those of previous studies by other authors on healthy controls. It is a helpful supplement to the reference value pool of CNE-SFEMG of the frontalis. Introducing patients with confusing diseases into the reference population will increase the ability of this technique to differentiate MG from non-NMT disorders.

Improved TARP development based upon mine specific data

The trigger action response plans (TARPs) are inherent to managing the multiple hazards such as: high gas content with multiple coal seams, high spontaneous combustion (sponcom) propensity, heat and ventilation. TARPs aim to provide assurance and guidance when the situation deviates from the original plan or there is a change conditions that could be hazardous. Over the years, learnings from various incidents has continuously required the coal operations to re-visit the TARP trigger values that were based on historic data or based on guidance values from the industry. In most cases, the background to the basis of TARP statistical data, viz., average, maximum, hourly, daily for the monitoring or sampling location is also unknown. Introduction of real-time monitoring devices to monitor the gases and airflows has provided greater understanding of the hazard scenarios and their controls. This paper analyses the carbon monoxide data from operating longwall mines and compares these with the historic trigger values to understand the changes and determine improvement opportunities while setting trigger levels in the TARPs. As an example of setting trigger values, those used in during the sealing of a panel are explored in terms of setting values based upon the sampling location and the level of risk. It is envisaged that the learning’s shared herein would further enhance the understanding and management of multiple hazards in Australian coal mines.

Hadron Calorimeter (Projectile Spectator Detector—PSD) of NA61/SHINE experiment at CERN

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