Level Trigger Research Articles

Test bench for front end electronic of the GCT camera for the Cherenkov Telescope Array

The Gamma Cherenkov Telescope (GCT) is a design proposed to be part of the Small Sized Telescope (SST) array of the Cherenkov Telescope Array (CTA). The GCT camera is designed to record the flashes of atmospheric Cherenkov light from gamma and cosmic ray initiated cascades, which last only a few tens of nanoseconds. The camera thus needs very fast and compact electronics, addressed by the TARGET modules, based on homonymous ASICs which provide digitation at 1 GSample/s and the first level of trigger on the analog output of the photosensors. In this paper we describe a test bench lab set up to evaluate the performance and functionality of the camera' s front end electronics with an added educational value.

The evolution of the region of interest builder for the ATLAS experiment at CERN

The ATLAS detector uses a real time selective triggering system to reduce the high interaction rate from 40 MHz to its data storage capacity of 1 kHz. A hardware first level (L1) trigger limits the rate to 100 kHz and a software high level trigger (HLT) selects events for offline analysis. The HLT uses the Regions of Interest (RoIs) identified by L1 and provided by the Region of Interest Builder (RoIB). The current RoIB is a custom VMEbus based system that operated reliably since the first run of the LHC . Since the LHC will reach higher luminosity and ATLAS will increase the complexity and number of L1 triggers, it is desirable to have a more flexible and more operationally maintainable RoIB in the future. In this regard, the functionality of the multi-card VMEbus based RoIB is being migrated to a PC based RoIB with a PCI-Express card. Testing has produced a system that achieved the targeted rate of 100 kHz.

The NA62 spectrometer acquisition system

The NA62 low mass spectrometer consists of 7000 straw tubes operating in vacuum. The front-end electronics is directly mounted on the detector and connected by a flexible PCB. The front-end board provides the amplification, shaping, discrimination and time measurements of the analogue signals from 16 channels. After digitisation the data is sent to a VME 9U read-out board. The data, once matched with the trigger, is sent to the next step and used by the trigger level 1 algorithm. The front-end and read-out systems of the detector will be presented along with the first results of the detector performances.

Design of a hardware track finder (Fast Tracker) for the ATLAS trigger

The use of tracking information at the trigger level in the LHC Run II period is crucial for the trigger and data acquisition system and will be even more so as contemporary collisions that occur at every bunch crossing will increase in Run III. The Fast TracKer is part of the ATLAS trigger upgrade project; it is a hardware processor that will provide every Level-1 accepted event (100 kHz) and within 100μs, full tracking information for tracks with momentum as low as 1 GeV . Providing fast, extensive access to tracking information, with resolution comparable to the offline reconstruction, FTK will help in precise detection of the primary and secondary vertices to ensure robust selections and improve the trigger performance.

The Level-0 calorimetric trigger of the NA62 experiment

The NA62 experiment at the CERN SPS aims at measuring the branching ratio of the very rare kaon decay K+ → π+ ν ν̄ (expected 10−10) with a 10% background. Since an high-intensity kaon beam is required to collect enough statistics, the Level-0 trigger plays a fundamental role in both the background rejection and in the particle identification. The calorimetric trigger collects data from various calorimeters and it is able to identify clusters of energy deposit and determine their position, fine-time and energy. This paper describes the complete hardware commisioning and the setup of the trigger for the 2015 physics data taking.

A Pattern Recognition Mezzanine based on Associative Memory and FPGA technology for Level 1 Track Triggers for the HL-LHC upgrade

The increment of luminosity at HL-LHC will require the introduction of tracker information at Level-1 trigger system for the experiments in order to maintain an acceptable trigger rate for selecting interesting events despite the one order of increased magnitude in the minimum bias interactions. In order to extract the track information in the required latency (∼ 5–10 μ s depending on the experiment), a dedicated hardware processor needs to be used. We here propose a prototype system (Pattern Recognition Mezzanine) as core of pattern recognition and track fitting for HL-LHC experiments, combining the power of both Associative Memory custom ASIC and modern Field Programmable Gate Array (FPGA) devices.

Operation of the upgraded ATLAS Central Trigger Processor during the LHC Run 2

The ATLAS Central Trigger Processor (CTP) is responsible for forming the Level-1 trigger decision based on the information from the calorimeter and muon trigger processors. In order to cope with the increase of luminosity and physics cross-sections in Run 2, several components of this system have been upgraded. In particular, the number of usable trigger inputs and trigger items have been increased from 160 to 512 and from 256 to 512, respectively. The upgraded CTP also provides extended monitoring capabilities and allows to operate simultaneously up to three independent combinations of sub-detectors with full trigger functionality, which is particularly useful for commissioning, calibration and test runs. The software has also undergone a major upgrade to take advantage of all these new functionalities. An overview of the commissioning and the operation of the upgraded CTP during the LHC Run 2 is given.

The upgrade of the CMS Global Trigger

The Global Trigger is the final step of the CMS Level-1 Trigger. Previously implemented in VME, it has been redesigned and completely rebuilt in MicroTCA technology, using the Virtex-7 FPGA chip family. It will allow to implement trigger algorithms close to the final physics selection. The new system is presented, together with performance tests undertaken in parallel operation with the legacy system during the initial months of Run II of the LHC at a beam energy of 13 TeV.

The Read Out Controller for the ATLAS New Small Wheel

In the upgrade process of the ATLAS detector, the innermost stations of the endcaps (Small Wheels) will be replaced. The New Small Wheel will have two chamber technologies, small-strip Thin Gap Chambers and Micromegas, each providing triggering and precision track measurement. Custom front-end Application Specific Integrated Circuits will be used to read and filter information from both types of detectors. In the context of the New Small Wheel data path, the Read Out Controller ASIC is used for handling, preprocessing and formatting the data generated by the VMM upstream chips. The Read Out Controller will concentrate the data streams from 8 VMMs, filter data based on the ATLAS Level-1 trigger which identifies bunch crossings of interest and transmit the data to FELIX via the L1DDC. The Read Out Controller is composed of 8 VMM Capture modules, a cross-bar and 4 sROC modules. The output data is sent via up to 4 serial links with a configurable speed of 80, 160 or 320 Mbps per link.

FITPix COMBO—Timepix detector with integrated analog signal spectrometric readout

The hybrid semiconductor pixel detector Timepix has proven a powerful tool in radiation detection and imaging. Energy loss and directional sensitivity as well as particle type resolving power are possible by high resolution particle tracking and per-pixel energy and quantum-counting capability. The spectrometric resolving power of the detector can be further enhanced by analyzing the analog signal of the detector common sensor electrode (also called back-side pulse). In this work we present a new compact readout interface, based on the FITPix readout architecture, extended with integrated analog electronics for the detector's common sensor signal. Integrating simultaneous operation of the digital per-pixel information with the common sensor (called also back-side electrode) analog pulse processing circuitry into one device enhances the detector capabilities and opens new applications. Thanks to noise suppression and built-in electromagnetic interference shielding the common hardware platform enables parallel analog signal spectroscopy on the back side pulse signal with full operation and read-out of the pixelated digital part, the noise level is 600 keV and spectrometric resolution around 100 keV for 5.5 MeV alpha particles. Self-triggering is implemented with delay of few tens of ns making use of adjustable low-energy threshold of the particle analog signal amplitude. The digital pixelated full frame can be thus triggered and recorded together with the common sensor analog signal. The waveform, which is sampled with frequency 100 MHz, can be recorded in adjustable time window including time prior to the trigger level. An integrated software tool provides control, on-line display and read-out of both analog and digital channels. Both the pixelated digital record and the analog waveform are synchronized and written out by common time stamp.

Comparison of Pumping Regimes for Water Distribution Systems to Minimize Cost and Greenhouse Gases

AbstractA single-objective optimization model has been developed for water distribution system (WDS) pumping operations, considering five different types of pump operating regimes. These regimes use tank trigger levels, scheduling, and a combination of both to control pumps. A new toolkit development to alter rule-based controls in hydraulic simulation software has allowed more complex pump operating regimes than have previously been considered to be optimized. The performance of each of the regimes is compared with respect to two different objectives: cost and greenhouse gas (GHG) emissions, which were optimized separately to allow the comparison of regimes to be made more clearly. Two case study networks, including one that represents a segment of the South Australian WDS, illustrate the effectiveness of the model. Time-based scheduling operating strategies were found to perform better than the other types of pump operating regimes. Significant cost savings were achieved for the South Australian case st...

A Methodology for Pumping Control Based on Time Variable Trigger Levels

A methodology for the control of a pumping plant feeding a tank is presented. This methodology is aimed at minimizing the energy costs by maximizing pumping during off-peak electricity tariff periods. It is based on trigger levels which are variable during the day according to a prefixed pattern in order to ensure that the water level in the elevated tank is at its minimum and maximum values at the end of the peak and off-peak tariff periods respectively. The pattern of the trigger levels is defined by solving a multi-objective problem aimed at minimizing the energy costs and the number of pump switches.The methodology was applied to the real case of a pumping plant feeding an elevated tank for daily balance which, in turn, feeds a small town in northern Italy; one week of hourly observed total consumptions was considered. This methodology was compared with other two methodologies typically used for pump control, i.e. pump scheduling and fixed trigger levels. The results show that the proposed methodology allows for achieving energy costs that are definitively lower than those obtainable by using fixed trigger levels, and comparable with those obtainable by using pump scheduling, being the number of pump switches the same. On the other hand, unlike the pump scheduling, the methodology presented does not require any water demand forecast and scheduling optimization to be repeated daily, thus representing an effective and efficient tool for pumping plant operation.

Transfusion medicine in practice.

The safety and stability of the supply of blood products must be ensured for appropriate blood transfusion therapy. Various security measures need to be taken and a balanced blood donation system should be maintained by the Japanese Red Cross Society. Based on such a system, each institute needs to establish a proper management protocol and to assure adequate use of blood products, as well as creating measures to deal with adverse events associated with blood transfusion. The system for preventing transfusion errors is particularly essential. For appropriate use of blood products, the "Guideline for the Use of Blood Products" should be followed, and unnecessary use should be avoided. These are prerequisites for error-free treatment of patients. In this educational lecture, major points in performing blood transfusion in clinical practice, such as proper indications for the use of blood products associated with patient conditions or trigger levels, and important points as well as contraindications when using blood products, such as the speed of administration, will be discussed.

Full Offline Reconstruction in Real Time with the LHCb Detector

This document describes the novel, unique in High Energy Physics, real-time alignment and calibration of the full LHCb detector. The LHCb experiment has been designed as a dedicated heavy flavour physics experiment focused on the reconstruction of c and b hadrons. The LHCb detector is a single-arm forward spectrometer, which measures proton-proton interactions at the LHC. The operational bunch crossing rate is several orders of magnitude above the current abilities of data recording and storage. Therefore, a trigger system has been implemented to reduce this rate to an acceptable value. The LHCb trigger system has been redesigned during the 2013–2015 long shutdown,achieving offline-quality alignment and calibration online. It also allows analyses to be performed entirely at the trigger level. In addition, having the best performing reconstruction in the trigger gives the possibility to fully use the particle identification selection criteria and greatly increases the efficiency, in particular for the selection of charm and strange hadron decays. This results in enhancing the physics programme of the LHCb experiment.

FPGA-Based Approach to Level-1 Track Finding at CMS for the HL-LHC

The high luminosity upgrade of the LHC is expected to deliver luminosities of 7.5 × 10 34 cm −2 s −1 , with an average of 140–200 overlapping proton-proton collisions in each bunch crossing at a frequency of 40 MHz. To maintain manageable trigger rates under these conditions track reconstruction will be incorporated in the all-hardware first level of the CMS trigger. A track-finding algorithm based on seed tracklets has been developed and implemented on commercially available FPGAs for this purpose. An overview of the algorithm is presented, results are shown of its expected performance from simulations, and an implementation of the algorithm in a Xilinx Virtex-7 FPGA for a hardware demonstrator system is discussed.

A new ATLAS muon CSC readout system with system on chip technology on ATCA platform

The ATLAS muon Cathode Strip Chamber (CSC) backend readout system has been upgraded during the LHC 2013-2015 shutdown to be able to handle the higher Level-1 trigger rate of 100 kHz and the higher occupancy at Run-2 luminosity. The readout design is based on the Reconfigurable Cluster Element (RCE) concept for high bandwidth generic DAQ implemented on the Advanced Telecommunication Computing Architecture (ATCA) platform. The RCE design is based on the new System on Chip XILINX ZYNQ series with a processor-centric architecture with ARM processor embedded in FPGA fabric and high speed I/O resources. Together with auxiliary memories, all these components form a versatile DAQ building block that can host applications tapping into both software and firmware resources. The Cluster on Board (COB) ATCA carrier hosts RCE mezzanines and an embedded Fulcrum network switch to form an online DAQ processing cluster. More compact firmware solutions on the ZYNQ for high speed input and output fiberoptic links and TTC allowed the full system of 320 input links from the 32 chambers to be processed by 6 COBs in one ATCA shelf. The full system was installed in September 2014. We will present the RCE/COB design concept, the firmware and software processing architecture, and the experience from the intense commissioning for LHC Run 2.

Performance Studies of Micromegas Chambers for the New Small Wheel Upgrade Project

The ATLAS collaboration has chosen the Micromegas technology along with the small-strip Thin Gap Chambers for the upgrade of the inner muon station in the high-rapidity region, the so called New Small Wheel upgrade project. It will employ eight layers of Micromegas and eight layers of small-strip Thin Gap Chambers per wheel. The New Small Wheel project requires fully efficient Micromegas chambers, able to cope with the maximum expected rate of 15 kHz/cm 2 featuring single plane spatial resolution better than 100 μm. The Micromegas detectors will cover a total active area of ~ 1200 m 2 and will be operated in a moderate magnetic field (≤ 0.3 T). Moreover, together with their precise tracking capability the New Small Wheel Micromegas chambers will contribute to the ATLAS Level-1 trigger system. Several studies have been performed on small (10 × 10 cm 2 ) and medium (1 × 0.5 m 2 ) size prototypes using medium (1 − 5 GeV/c) and high momentum (120 – 150 GeV/c) hadron beams at CERN. A brief overview of the results obtained is presented.

Online Reconstruction and Calibration with Feedback Loop in the ALICE High Level Trigger

ALICE (A Large Heavy Ion Experiment) is one of the four large scale experiments at the Large Hadron Collider (LHC) at CERN. The High Level Trigger (HLT) is an online computing farm, which reconstructs events recorded by the ALICE detector in real-time. The most compute-intense task is the reconstruction of the particle trajectories. The main tracking devices in ALICE are the Time Projection Chamber (TPC) and the Inner Tracking System (ITS). The HLT uses a fast GPU-accelerated algorithm for the TPC tracking based on the Cellular Automaton principle and the Kalman filter. ALICE employs gaseous subdetectors which are sensitive to environmental conditions such as ambient pressure and temperature and the TPC is one of these. A precise reconstruction of particle trajectories requires the calibration of these detectors. As first topic, we present some recent optimizations to our GPU-based TPC tracking using the new GPU models we employ for the ongoing and upcoming data taking period at LHC. We also show our new approach for fast ITS standalone tracking. As second topic, we present improvements to the HLT for facilitating online reconstruction including a new flat data model and a new data flow chain. The calibration output is fed back to the reconstruction components of the HLT via a feedback loop. We conclude with an analysis of a first online calibration test under real conditions during the Pb-Pb run in November 2015, which was based on these new features.

Study of the Radiation Induced Effects in the LHCb Vertex Locator

LHCb is a dedicated heavy-flavour physics experiment at the Large Hadron Collider at CERN. The VErtex LOcator (VELO) is a critical part of a LHCb tracking system, enabling the full topological reconstruction of beauty and charm mesons’ decays and providing essential input for the High Level Trigger (HLT) system used by the experiment to select events. The VELO comprises 42 modules made of two n-on-n 300 μm thick halfdisc silicon sensors with Rand Φ-measuring micro-strips, arranged in two retractable halves, operating only about 8 mm from the proton beams. In these paper, selected aspects of the VELO performance during the Run 1 data-taking period is shortly summarised along with the radiation damage studies. The track finding efficiency is typically greater than 98%. An impact parameter resolution of less than 35 μm is achieved for particles with transverse momentum greater than 1 GeV/c. An overview of all important performance parameters will be given. The VELO sensors have received a large and non-uniform radiation dose of up to 1.2 × 10 1 MeV neutron equivalent cm−2. Silicon-type inversion has been observed in regions close to the interaction point.

Machine Learning and Parallelism in the Reconstruction of LHCb and its Upgrade

The LHCb detector at the LHC is a general purpose detector in the forward region with a focus on reconstructing decays of c- and b-hadrons. For Run II of the LHC, a new trigger strategy with a real-time reconstruction, alignment and calibration was employed. This was made possible by implementing an offline-like track reconstruction in the high level trigger. However, the ever increasing need for a higher throughput and the move to parallelism in the CPU architectures in the last years necessitated the use of vectorization techniques to achieve the desired speed and a more extensive use of machine learning to veto bad events early on. This document discusses selected improvements in computationally expensive parts of the track reconstruction, like the Kalman filter, as well as an improved approach to get rid of fake tracks using fast machine learning techniques. In the last part, a short overview of the track reconstruction challenges for the upgrade of LHCb, is given. Running a fully software-based trigger, a large gain in speed in the reconstruction has to be achieved to cope with the 40 MHz bunch-crossing rate. Two possible approaches for techniques exploiting massive parallelization are discussed.