First-level Trigger Research Articles

Fast muon tracking with machine learning implemented in FPGA

In this work, we present a new approach for fast tracking on multiwire proportional chambers with neural networks. The tracking networks are developed and adapted for the first-level trigger at hadron collider experiments. We use Monte Carlo samples generated by Geant4 with a custom muon chamber, which resembles part of the thin gap chambers from the ATLAS experiment, for training and performance evaluations. The chamber has a total of seven gas gaps, where the first and last gas gaps are displaced by ∼1.5 m. Each gas gap has 50 channels with a size of 18–20 mm. Two neural network models are developed and presented: a convolutional neural network and a neural network optimized for the detector configuration of this study. In the latter network, a convolution layer is provided for each of three groups formed from 2–3 gas gaps of the chamber, and the outputs are fed into multilayer perceptrons in sequence. Both networks are transformed into hardware description language and implemented in Virtex UltraScale+ FPGA. The angular resolution is 2 mrad, which is comparable to the maximum resolution of the detector estimated by the minimum χ2 method. The latency achieved by the implemented firmware is less than 100 ns, and the throughput rate is 160 MHz.

The Data Acquisition System for the ATLAS Tile Calorimeter Phase-II Upgrade Demonstrator

The tile calorimeter (TileCal) is the central hadronic calorimeter of the ATLAS experiment at the large hadron collider (LHC). In 2025, the LHC will be upgraded leading to the high luminosity LHC (HL-LHC). The HL-LHC will deliver an instantaneous luminosity up to seven times larger than the LHC nominal luminosity. The ATLAS Phase-II upgrade (2025–2027) will accommodate the subdetectors to the HL-LHC requirements. As part of this upgrade, the majority of the TileCal on-detector and off-detector electronics will be replaced using a new readout strategy, where the on-detector electronics will digitize and transmit digitized detector data to the off-detector electronics at the bunch crossing frequency (40 MHz). In the counting rooms, the off-detector electronics will compute reconstructed trigger objects for the first-level trigger and will store the digitized samples in pipelined buffers until the reception of a trigger acceptance signal. The off-detector electronics will also distribute the LHC clock to the on-detector electronics embedded within the digital data stream. The TileCal Phase-II upgrade project has undertaken an extensive research and development program that includes the development of a Demonstrator module to evaluate the performance of the new clock and readout architecture envisaged for the HL-LHC. The Demonstrator module equipped with the latest version of the on-detector electronics was built and inserted into the ATLAS experiment. The Demonstrator module is operated and read out using a Tile PreProcessor (TilePPr) Demonstrator which enables backward compatibility with the present ATLAS Trigger and Data AcQuisition (TDAQ), and the timing, trigger, and command (TTC) systems. This article describes in detail the main hardware and firmware components of the clock distribution and data acquisition systems for the Demonstrator module, focusing on the TilePPr Demonstrator.

Electromagnetic calorimeter of Belle II

The electromagnetic calorimeter of the Belle II detector and its performance in the first SuperKEKB run during 2018 are described. It is a high-granularity calorimeter based on 8736 CsI(Tl) scintillating crystals. The scintillation light is detected by PIN photodiodes. Each calorimeter electronics readout channel includes a charge sensitive preamplifier attached to the crystal and a 2 MHz flash ADC followed by a wave form analysis (WFA) realized in FPGA which provides both amplitude and time reconstruction. Usage of the WFA reduces a contribution of the pile-up noise. High time resolution provides the beam background suppression. In the Belle II experiment the calorimeter is used for particle energy measurement, particle identification as well as for the collider luminosity measurement, it also contributes to the first-level trigger.

Performance results of the trigger logic implemented in EUSO-SPB

Abstract EUSO-SPB (Extreme Universe Space Observatory-Super Pressure Balloon) was the first mission of the JEM-EUSO program which implemented the First Level Trigger (FLT) logic to detect Ultra-High Energy Cosmic Rays (UHECRs) following the scheme developed for the JEM-EUSO mission. Experimental results matched the expected behavior of the logic and satisfied the requirements conceived for the FLT. The sensitivity of EUSO-SPB to the detection of UHECRs was established.

The new octal amplifier–shaper–discriminator chip for the ATLAS MDT chambers at HL-LHC

In order to fully exploit the physics potential of the ATLAS experiment at the HL-LHC, the trigger rate of and maximum latency of the first-level trigger system will be increased to 1 MHz and 10 μ s , respectively. In addition, a new first-level muon track trigger with high momentum resolution based on the ATLAS precision Muon Drift-Tube (MDT) chambers will be employed which requires triggerless readout. The TDC ASICs of the current front-end electronics of the MDT chambers are incompatible with these requirements. The front-end boards, each with a TDC chip and three 8-channel amplifier–shaper–discriminator (ASD) chips have to be replaced. Therefore, a new octal ASD2 ASIC has been developed in modern 130 nm IBM/Global Foundries CMOS technology. The chip also contains a Wilkinson ADC to perform both time-over-threshold and signal charge measurement. The ASD design has been fully qualified for the serial production of 80000 chips for ATLAS. The performance in terms of signal rise time and channel uniformity significantly surpasses the one of the previous chip while keeping the power consumption constant. In addition to the characterization with test pulses, several chips have been mounted on the front-end boards and tested in a muon beam at the Gamma Irradiation Facility GIF++ at CERN up to high counting rates where the superior drift time and spatial resolution becomes evident. • New Amplifier–Shaper–Discriminator chips for the readout of ATLAS (s)MDT chambers at HLLHC. • Design of new ASD chip in 130 nm CMOS IBM/Global Foundries technology completed. • Improved signal rise time and channel uniformity. • Radiation hardness far better than needed in the ATLAS muon spectrometer at HLLHC. • Successful full performance test in a muon beam at CERN under intense gamma irradiation.

Track Finding in CMS for the Level-1 Trigger at the HL-LHC

The High Luminosity LHC (HL-LHC) will deliver luminosities of up to 5 × 1034 Hz/cm2, with an average of about 140 overlapping proton-proton collisions per bunch crossing. These extreme pileup conditions place stringent requirements on the trigger system to be able to cope with the resulting event rates. A key component of the CMS upgrade for HL-LHC is a track trigger system which would identify tracks with transverse momentum above 2 GeV/c already at the first-level trigger. This paper presents the status of proposals for implementing the L1 tracking in conjunction with the planned upgrade for the silicon tracker of the CMS experiment.

Associative Memory Pattern Matching for the L1 Track Trigger of CMS at the HL-LHC

The High Luminosity LHC (HL-LHC) will deliver a luminosity of up to 5 × 10 34 cm −2 s −1 , with an average of about 140 overlapping proton-proton collisions per bunch crossing. These extreme pileup conditions place stringent requirements on the trigger system to be able to cope with the resulting event rates. A key component of the CMS upgrade for HL-LHC is a track trigger system, able to identify tracks with transverse momenta above 2 GeV/c already at the first-level trigger. We present here the status of the implementation of a prototype system, based on the combination of Associative Memory custom ASIC and modern Field Programmable Gate Array (FPGA) devices, with the purpose to demonstrate the concept based on state-of-the-art technologies, and to direct the efforts of the necessary R&D toward a final system.

L1 track triggering at CMS for High Luminosity LHC

The High Luminosity LHC (HL-LHC) is expected to deliver luminosities of 5 × 1034 c -2 -1, with an average number of overlapping proton-proton collisions per bunch crossing (pileup) of about 140. These extreme pileup conditions place stringent requirements on the experiments' trigger systems to cope with the resulting event rates. For the CMS experiment, a key component of the detector upgrade for the HL-LHC is a track-trigger system which would identify tracks with transverse momentum above 2 GeV already at the first-level (L1) trigger. Here, a proposal for implementing L1 tracking using ``tracklets" is presented. The expected performance of the L1 tracking from simulation studies and the use of L1 tracks to define trigger objects are discussed.

The evolution of the Trigger and Data Acquisition System in the ATLAS experiment

The ATLAS experiment, aimed at recording the results of LHC proton-proton collisions, is upgrading its Trigger and Data Acquisition (TDAQ) system during the current LHC first long shutdown. The purpose of the upgrade is to add robustness and flexibility to the selection and the conveyance of the physics data, simplify the maintenance of the infrastructure, exploit new technologies and, overall, make ATLAS data-taking capable of dealing with increasing event rates. The TDAQ system used to date is organised in a three-level selection scheme, including a hardware-based first-level trigger and second- and third-level triggers implemented as separate software systems distributed on separate, commodity hardware nodes. While this architecture was successfully operated well beyond the original design goals, the accumulated experience stimulated interest to explore possible evolutions. We will also be upgrading the hardware of the TDAQ system by introducing new elements to it. For the high-level trigger, the current plan is to deploy a single homogeneous system, which merges the execution of the second and third trigger levels, still separated, on a unique hardware node. Prototyping efforts already demonstrated many benefits to the simplified design. In this paper we report on the design and the development status of this new system.

Development of an Endcap DIRC for PANDA

The aim of this research is to develop a planar DIRC detector showing advantages and performance similar to a classical, barrel shaped DIRC, but at smaller polar angles which cannot be accessed using a cylindrical geometry. The device will complement the PANDA Barrel DIRC by covering polar angles from 5° to 22°. The envisaged π/K-separation is ≥3σ up to 4GeV/c.A major challenge is the adaption of the device to the PANDA environment including a magnetic field of ~1–2T, high rates and radiation, limited space for optics and sensors as well as the lack of a common first-level trigger. This paper discusses a detector design which forms a compromise between these constraints and available hardware, a specific analytic reconstruction method, a performance estimation based on Geant4 simulations and finally the successful particle identification using a recent R&D prototype.

Upgraded Readout Electronics for the ATLAS Liquid Argon Calorimeters at the High Luminosity LHC

The ATLAS liquid-argon calorimeters produce a total of 182,486 signals which are digitized and processed by the front-end and back-end electronics at every triggered event. In addition, the front-end electronics sum analog signals to provide coarsely grained energy sums, called trigger towers, to the first-level trigger system, which is optimized for nominal LHC luminosities. However, the pile-up background expected during the high luminosity phases of the LHC will be increased by factors of 3 to 7. An improved spatial granularity of the trigger primitives is therefore proposed in order to improve the identification performance for trigger signatures, like electrons or photons, at high background rejection rates. For the first upgrade phase in 2018, new Liquid Argon Trigger Digitizer Boards are being designed to receive higher granularity signals, digitize them on detector and send them via fast optical links to a new, off-detector digital processing system. The digital processing system applies digital filtering and identifies significant energy depositions. The refined trigger primitives are then transmitted to the first level trigger system to extract improved trigger signatures. The general concept of the upgraded liquid-argon calorimeter readout together with the various electronics components to be developed for such a complex system is presented. The research activities and architectural studies undertaken by the ATLAS Liquid Argon Calorimeter Group are described, particularly details of the on-going design of mixed-signal front-end electronics, of radiation tolerant optical-links, and of the high-speed off-detector digital processing system.

Upgraded readout electronics for the ATLAS LAr calorimeter at the phase I of LHC

The ATLAS Liquid Argon (LAr) calorimeters produce a total of 182,486 signals which are digitized and processed by the front-end and back-end electronics at every triggered event. In addition, the front-end electronics is summing analog signals to provide coarsely grained energy sums, called trigger towers, to the first-level trigger system, which is optimized for nominal LHC luminosities. However, the pile-up noise expected during the high luminosity phases of LHC will be increased by factors of 3–7. An improved spatial granularity of the trigger primitives is therefore proposed in order to improve the identification performance for trigger signatures, like electrons or photons, at high background rejection rates. The general concept of the upgraded LAr calorimeter readout together with the various electronics components to be developed for such a complex system is presented. The R&D activities and architectural studies undertaken by the ATLAS LAr Calorimeter group are described.

The data acquisition and transport design for NEMO Phase 2

Many high energy physics experiments (Auger, IceCube, NEMO, Km3Net) currently taking data or planned in the near future consist of big and sparse detectors that acquire a huge amount of data. This kind of topology requires the ability to acquire physics information in different places of the detector and correlate them using the occurrence time, usually with a sub-ns precision. The architecture described here provides a real-time data transport layer, used to implement the data acquisition system for the NEMO experiment, and consists of a synchronous link with fixed and deterministic latency. The system clock, distributed at every level of the apparatus, has been derived by the signals provided by a GPS receiver during the operating configuration. The aim of this contribution is to give an overview of the NEMO electronic system: the underwater electronics sample signals from photomultipliers and acquires slow-control data from both oceanographic instruments and dedicated sensors, allowing to monitor the operational conditions of the apparatus. The whole data are sent to the laboratory through a fully bi-directional fiber optic link. On-shore the data are received by dedicated boards that distribute them to the first-level trigger and to the slow-control system. A description of the different stages of data acquisition and transport will be given.

ATLAS TDAQ System: Current Status and Performance

Abstract In this paper we will report on the operation and the performance of the ATLAS data-flow system during the 2011 physics run of the Large Hadron Collider at 7 TeV. The data-flow system is responsible for reading out, formatting and conveying the event data, eventually saving the selected events into the mass storage. In 2010 the ATLAS Trigger and Data Acquisition system has been operated with an overall e_ciency of 96%, while meeting evolving and demanding conditions. By the end of the proton run, the instantaneous peak luminosity had increased by 5 orders of magnitudes. Correspondingly, the ATLAS first-level trigger rate grew by a factor 100, reaching 40 kHz, roughly half of the design rate. Concurrently, the event building and data saving rates reached and exceeded the design performance. Moreover, the installation of additional computing power yielded a system whose characteristics are now comparable with the final ones. In this paper we report on achievements and problems encountered during 2010 and 2011. On this basis, we will follow discussing the preparations for the remaining 2011 data-taking period, in particular with respect to the expected increase in luminosity and the predicted reaching of the design first-level trigger rate.

The Performance of the ATLAS Trigger System in the LHC Proton-Proton Collisions

In this paper we will report on the operation and the performance of the ATLAS data-flow system during the 2011 physics run of the Large Hadron Collider at 7 TeV. The data-flow system is responsible for reading out, formatting and conveying the event data, eventually saving the selected events into the mass storage. In 2010 the ATLAS Trigger and Data Acquisition system has been operated with an overall efficiency of 96%, while meeting evolving and demanding conditions. By the end of the proton run, the instantaneous peak luminosity had increased by 5 orders of magnitudes. Correspondingly, the ATLAS first-level trigger rate grew by a factor 100, reaching 40 kHz, roughly half of the design rate. Concurrently, the event building and data saving rates reached and exceeded the design performance. Moreover, the installation of additional computing power yielded a system whose characteristics are now comparable with the final ones. In this paper we report on achievements and problems encountered during 2010 and 2011. On this basis, we will follow discussing the preparations for the remaining 2011 data-taking period, in particular with respect to the expected increase in luminosity and the predicted reaching of the design first-level trigger rate.

The ATLAS trigger - commissioning with cosmic rays

The ATLAS detector at CERN's LHC will be exposed to proton-proton collisions from beams crossing at 40 MHz. At the design luminosity there are roughly 23 collisions per bunch crossing. ATLAS has designed a three-level trigger system to select potentially interesting events. The first-level trigger, implemented in custom-built electronics, reduces the incoming rate to less than 100 kHz with a total latency of less than 2.5μs. The next two trigger levels run in software on commercial PC farms. They reduce the output rate to 100-200 Hz.In preparation for collision data-taking which is scheduled to commence in May 2008, several cosmic-ray commissioning runs have been performed. Among the first sub-detectors available for commissioning runs are parts of the barrel muon detector including the RPC detectors that are used in the first-level trigger. Data have been taken with a full slice of the muon trigger and readout chain, from the detectors in one sector of the RPC system, to the second-level trigger algorithms and the data-acquisition system. The system is being prepared to include the inner-tracking detector in the readout and second-level trigger.We will present the status and results of these cosmic-ray based commissioning activities. This work will prove to be invaluable not only during the commissioning phase but also for cosmic-ray data-taking during the normal running for detector performance studies.

Commissioning with cosmic rays of the muon spectrometer of the ATLAS experiment at the large hadron collider

The Muon Spectrometer of the ATLAS experiment is made of large toroidal magnets, arrays of high-pressure drift tubes for precise tracking and dedicated fast detectors for the first-level trigger. All the detectors in the barrel toroid have been installed and commissioning has started with cosmic rays. These detectors are arranged in three concentric rings and the total area is about 6000 square meters. During the installation and commissioning of the detectors, data are usually taken with the magnet off, but a dedicated run took place with the magnetic field of the barrel toroid turned on. We present the procedure to control the response of the single detectors installed in the barrel toroid, Monitored Drift Tubes and Resistive Plate Chambers, and results of the first tests done with cosmic rays triggered by the first-level processor and read-out trough the ATLAS data acquisition. Details on the installation and commissioning schedule will be given in view of the completion of the instrumentation of the muon spectrometer for the first period of data taking with proton-proton collisions.

Commissioning of the ATLAS Level-1 trigger with cosmic rays

The ATLAS detector at CERN's Large Hadron Collider will be exposed to proton-proton collisions from beams crossing at 40 MHz. A three-level trigger system was designed to select potentially interesting events and reduce the incoming rate to 100-200 Hz. The first trigger level (LVL1) is implemented in custom-built electronics, the second and third trigger levels are realized in software. Based on calorimeter information and hits in dedicated muon-trigger detectors, the LVL1 decision is made by the central-trigger processor yielding an output rate of less than 100 kHz. The allowed latency for the trigger decision at this stage is less than 2.5 microseconds. Installation of the final LVL1 trigger system at the ATLAS site is in full swing, to be completed later this year. We present a status report of the main components of the first-level trigger and the in-situ commissioning of the full trigger chain with cosmic-ray muons.

Validation Tools for ATLAS Muon Spectrometer Commissioning

The ATLAS Muon Spectrometer (MS), currently being installed at CERN, is designed to measure final state muons of 14 TeV proton-proton interactions at the Large Hadron Collider (LHC) with a good momentum resolution of 2–3% at 10–100 GeV/c and 10% at 1 TeV, taking into account the high level background enviroment, the inhomogeneous magnetic field, and the large size of the apparatus (24 m diameter by 44 m length). The MS layout of the ATLAS detector is made of a large toroidal magnet, arrays of high-pressure drift tubes for precise tracking and dedicated fast detectors for the first-level trigger, and is organized in eight Large and eight Small sectors. All the detectors of the barrel toroid have been installed and the commissioning has started with cosmic rays. In order to validate the MS performance using cosmic events, a Muon Commissioning Validation package has been developed and its results are presented in this paper. Integration with the rest of the ATLAS sub-detectors is now being done in the ATLAS cavern.

Data taking system for the NEMO experiment

A four-floors prototype of the NEMO towers has been successfully deployed off the Sicily coast in December 2006. The aim of this contribution is to give an overview of the NEMO electronic system and to explain the different stages of data acquisition and transport.The underwater electronics sample signals from photomultipliers and acquire slow-control data both from oceanographic instruments and dedicated sensors, allowing to monitor the operational conditions of the apparatus.The whole data are sent to the laboratory through a fully bi-directional fiber optic link. On-shore the data are received by dedicated boards that distribute them to first-level trigger and to the slow-control system.The NEMO data acquisition/transmission electronic system will be described, properties of acquired signals and of data flow will be discussed.