The increase in luminosity, and consequent higher backgrounds, of the LHC upgrades require improved rejection of fake tracks in the forward region of the ATLAS Muon Spectrometer. The New Small Wheel upgrade of the Muon Spectrometer aims to reduce the large background of fake triggers from track segments that are not originated from the interaction point. The New Small Wheel employs two detector technologies, the resistive strip Micromegas detectors and the "small" Thin Gap Chambers, with a total of 2.45 Million electrodes to be sensed. The two technologies require the design of a complex electronics system given that it consists of two different detector technologies and is required to provide both precision readout and a fast trigger. It will operate in a high background radiation region up to about 20 kHz/cm$^{2}$ at the expected HL-LHC luminosity of $\mathcal{L}$=7.5$\times10^{34}$cm$^{-2}$s$^{-1}$. The architecture of the system is strongly defined by the GBTx data aggregation ASIC, the newly-introduced FELIX data router and the software based data handler of the ATLAS detector. The electronics complex of this new detector was designed and developed in the last ten years and consists of multiple radiation tolerant Application Specific Integrated Circuits, multiple front-end boards, dense boards with FPGA's and purpose-built Trigger Processor boards within the ATCA standard. The New Small Wheel has been installed in 2021 and is undergoing integration within ATLAS for LHC Run 3. It should operate through the end of Run 4 (December 2032). In this manuscript, the overall design of the New Small Wheel electronics is presented.

We present a detector-emulation method for developing, optimizing, and testing front-end electronics for particle detectors under realistic experimental conditions. The method is capable of reproducing bipolar signals shape and amplitude, rates, pileup, and radiation backgrounds. By controlling the different components of the experimental environment, the method allows for the assessment of their individual and combined effects, which is difficult to achieve in test beam or experiment environment. The technique emulates the output current of AC coupled detector terminals for an experimental environment of interest, by combining a sequence of recorded or simulated signal waveforms. Voltage waveforms produced with off the shelf arbitrary waveform generators are converted to current by a simple circuit, which also accounts for the characteristic capacitance of the detector, and injected into the front-end electronics. We demonstrate the technique by applying it in the optimization and characterization of the front-end electronics of the sTGC detector for the ATLAS experiment.

This paper describes the data acquisition and high level trigger system of the ATLAS experiment at the Large Hadron Collider at CERN, as deployed during Run 1. Data flow as well as control, configuration and monitoring aspects are addressed. An overview of the functionality of the system and of its performance is presented and design choices are discussed.

The instantaneous luminosity of the Large Hadron Collider at CERN will be increased up to a factor of five with respect to the present design value by undergoing an extensive upgrade program over the coming decade. The most important upgrade project for the ATLAS Muon System is the replacement of the present first station in the forward regions with the so-called New Small Wheels (NSWs). The NSWs will be installed during the LHC long shutdown in 2019/2020. Small-Strip Thin Gap Chamber (sTGC) detectors are designed to provide fast trigger and high precision muon tracking under the high luminosity LHC conditions. To validate the design, a full-size prototype sTGC detector of approximately 1.2 x 1.0 m(2) consisting of four gaps has been constructed. Each gap provides pad, strip and wire readouts. The sTGC intrinsic spatial resolution has been measured in a 32 GeV pion beam test at Fermilab. At perpendicular incidence angle, single gap position resolutions of about 50 Lim have been obtained, uniform along the sTGC strip and perpendicular wire directions, well within design requirements. Pad readout measurements have been performed in a 130 GeV muon beam test at CERN. The transition region between readout pads has been found to be 4 mm, and the pads have been found to be fully efficient. (C) 2016 Published by Elsevier B.V.

The forthcoming luminosity upgrade of LHC to super-LHC (sLHC) will increase the expected background rate in the forward region of the ATLAS Muon Spectrometer by approximately the factor of five. Some of the present Muon Spectrometer components will fail to cope with these high rates and will have to be replaced. The results of a test of a device consisting of Thin Gap Chambers (TGC) and a fast small-diameter Muon Drift Tube Chamber (sMDT) using the 180 GeV/c muons at the SPS-H8 muon beam at CERN are presented. The goal of the test was to study the combined TGC-sMDT system as tracking and triggering device in the ATLAS muon spectrometer after high-luminosity upgrades of the LHC. The analysis of the recorded data shows a very good correlation between the TGC and sMDT track position and inclination. This technology offers the combination of trigger and tracking and has good angular and spatial resolutions. The angular resolution is 0.4 mrad for each system individually. For the spatial resolution, the width of the track residual between TGC and sMDT is 104 μm at zero degree impact angle.

The DAQ/HLT system of the ATLAS experiment at CERN, Switzerland, is being commissioned for first collisions in 2009. Presently, the system is composed of an already very large farm of computers that accounts for about one-third of its final event processing capacity. Event selection is conducted in two steps after the hardware-based Level-1 Trigger: a Level-2 Trigger processes detector data based on regions of interest (RoI) and an Event Filter operates on the full event data assembled by the Event Building system. The detector read out is fully commissioned and can be operated at its full design capacity. This places the responsibility on the High-Level Triggers system to select only events of highest physics interest that will finally reach the offline reconstruction farms. This paper brings an overview of the current ATLAS DAQ/HLT implementation and performance based on studies originated from its operation with simulated, cosmic particles and first-beam data. Its built-in event processing parallelism is presented and discussed.

In 2004, a combined system test was performed in the H8 beam line at the CERN SPS with a setup reproducing the geometry of sectors of the ATLAS Muon Spectrometer, formed by three stations of Monitored Drift Tubes (MDT). The full ATLAS analysis chain was used to obtain the results presented in this paper. The basic design performances of the Muon Spectrometer were verified. The stability of MDT calibration constants, the alignment system using optical devices and high energy tracks, as well as the intrinsic sagitta resolution of the Muon Spectrometer were studied and found to agree with expectations. The reconstruction of muon tracks using the combined information from both the Inner Detector and the Muon Spectrometer are also presented.

Y. Okumuraa, S. Hasegawaa, T. Sugimotoa, Y. Takahashia, M. Tomotoa, C. Fukunagab, M. Ikenoc, H. Iwasakic, K. Naganoc, M. Nozakic, O. Sasakic, Y. Suzukic, S. Tanakac, Y. Yasuc, Y. Hasegawad, H. Oshitad,T. Takeshitad, M. Nomachie,Y. Sugayae, S. Hirayamaf, M. Ishinof, N. Kanayaf, F. Kanegaf, T. Kawamotof, K. Kessokuf, T. Kobayashif, T. Kubotaf, H. Nomotof, H. Sakamotof, T. Hayakawag, A. Ishikawag, T. Kadosakag, K. Kawagoeg, H. Kiyamurag, H. Kurashigeg, T. Matsushitag, H. Nakatsukag, T. Niwag, A. Ochig, C. Omachig, H. Takedag , N. Lupuh, S. Bresslerh, S. Taremh, E. Kajomovitzh, S. Ben Amih, A. Hershenhornh, Y. Benhammoui, E. Etzioni, D. Lellouchj, L. Levinsonj, G. Mikenbergj, A. Roichj

We report on the ATLAS commissioning run from the view point of the Thin Gap Chamber (TGC), which is the ATLAS end cap muon trigger detector. All the TGC sectors with on-detector electronics are going to be installed to the ATLAS cavern by the end of September 2007. To integrate all sub-detectors before the physics run starting from early 2008, the global commissioning run together with other sub-detectors has been performed from June 2007. We have evaluated the performance of the complete trigger chain of the TGC electronics and provide the trigger signal using cosmic-ray to the sub-systems in the global run environment.

The detector at CERN's large hadron collider (LHC) was exposed to proton-proton collisions from beams crossing at 40 MHz. A three-level trigger system will select potentially interesting events in order to reduce this rate to 100- 200 Hz. A trigger decision is made by the Level-1 central trigger processor (CTP) reducing the incoming rate to less than 100 kHz. The Level-1 decision is based on calorimeter information and hits in dedicated muon trigger detectors. The final Level-1 trigger system is currently being installed in the experiment with completion expected in autumn 2007. Cosmic ray data are regularly recorded as an increasing fraction of the trigger system comes online. We present an overview of the Level-1 trigger system architecture and report on the installation and commissioning process at the ATLAS experimental site. Emphasis is put on the integration of the CTP with the calorimeter and muon trigger systems. We show results from analyses of cosmic ray data recorded in situ and verify, where possible, that the Level-1 trigger meets the requirements and will be ready for data taking.

The ATLAS detector at CERN's Large Hadron Collider (LHC) will be exposed to proton-proton collisions from beams crossing at 40 MHz. A three-level trigger system will select potentially interesting events in order to reduce the read-out rate to about 200 Hz. The first trigger level is implemented in custom-built electronics and makes an initial fast selection based on detector data of coarse granularity. It has to reduce the rate by a factor of 104 to less than 100 kHz. The other two consecutive trigger levels are in software and run on PC farms. We present an overview of the first-level central trigger and the muon barrel trigger system and report on the current installation status. Moreover, we show analysis results of cosmic-ray data recorded in situ at the ATLAS experimental site with final or close-to-final hardware.

Thin gap chambers (TGCs) is the end-cap muon trigger detector of the ATLAS experiment, one of the major projects being built at CERN, Geneva, Switzerland. The TGC detector will be inaccessible during operation due to high radiation levels in the ATLAS cavern. The detector requires a detector-control system (DCS) to monitor important detector and environmental parameters, calibrate, set, and maintain the configuration of front-end electronics, and take appropriate corrective action to maintain the detector stability and reliable performance. the TGC DCS is a distributed system, comprising a central control and configuration master station, and about 1500 microcontroller slaves connected to it using a controller area network (CAN). The CAN nodes control hardware devices such as the thresholds for amplifier shaper discriminators (ASDs), and data-acquisition parameters. CAN nodes are distributed on the on-chamber trigger electronic boards, to service many channels close to their source. In contrast to many other control systems, the TGC DCS makes full use of the intelligence offered by the ATLAS ELMB CAN nodes, in order to distribute the control of complex tasks on the front-end nodes and reduce CAN bus traffic. These nodes implement JTAG and I2C protocols, monitor hardware parameters, generate test patterns, and histogram chamber charge for diagnostics. The hardware and software design, integration, performance, and radiation test results Are described.

The ATLAS Muon Spectrometer (ATLAS Collaboration, ATLAS Muon Spectrometer Technical Design Report CERN/LHCC/97-22, ATLAS TDR 10, 1997.) will use dedicated detectors to trigger on muons and to identify the bunch-crossing at the appropriate rate. The Spectrometer has been designed to perform stand-alone triggering and measurement of muon transverse momentum up to 1 TeV with good resolution (from 3% up to 10% at 1 TeV). The magnetic system is composed of three large superconducting air-core toroids instrumented with trigger and high-precision tracking chambers, a central part (barrel) composed of eight coils and two end-cap magnets. The high-precision tracking system is based on Monitored Drift Tube (MDT) and Cathode Strip Chambers (CSC) in the small angle-regions. The Level-1 trigger is provided by Resistive Plate Chambers (RPC) in the barrel and Thin Gap Chambers (TGC) in the end-cap. These detectors will also measure the track coordinates in the magnetic field direction (second coordinate), to complement the precision tracking provided by the MDT which only measure the track coordinates in the bending direction of the magnetic field. The trigger system covers an area of 3650 m2 in the barrel and 2900 m2 in the end-cap. In the barrel region three double-gap RPC stations are used, two in the middle and one in the outer MDT chamber layer. In the end-cap region one triple-gap TGC station is used, in front of the middle MDT station, and two double-gap TGC stations behind it. The mass production of both systems is under way. The systems were involved in extensive beam tests in 2002–2003, testing their compliance with LHC timing requirements using 25 ns beam bunching to emulate the LHC beam structure, aging under critical environment conditions and so on.

The ATLAS endcap muon trigger system uses custom integrated circuits and electronic modules. It will provide fast trigger information at the LHC bunchcrossing rate of 40 MHz to be used in making the first-level trigger decision. A prototype of the system has been constructed and mounted on Thin Gap Chambers. We have tested the system using a 180 GeV muon beam in the CERN SPS H8 beam line. The SPS provided bunched-beam with 25 ns structure, which allowed us to check the system performance under conditions very similar to the ATLAS experiment, before proceeding to the mass-production phase. We will present results on the evaluation of the system performance.

The TGC detector will be inaccessible during operation due to high radiation levels in the ATLAS cavern. The detector requires a Detector Control System (DCS) to monitor important detector and environmental parameters, calibrate, set and maintain the configuration of FE electronics, and take appropriate corrective action to maintain detector stability and reliable performance.The TGC DCS system makes full utilization of the intelligence offered by the ATLAS ELMB CAN nodes in order to distribute the control of complex tasks on the front-end nodes. Our hardware and software design, integration and radiation test results are described.

The first-level endcap muon trigger system have been designed for ATLAS experiment. The system has the main tasks which are to identify bunch crossings and to make trigger decisions for high transverse-momentum muon candidates. There are various requirements for trigger electronics to be satisfied, and several implementations using ASICs and FPGAs satisfy the requirement. We present the trigger scheme and overall of the system design.

We report on the measurements of the electron drift velocity and longitudinal diffusion in n-pentane gas mixtures and on the effect of the drift velocity on the timing properties of Thin Gap Chambers. Gas mixtures of n-pentane-CO2, n-pentane-CO2-CH4, and n-pentane-CO2-CF4 were investigated.An increase of the drift velocity has been observed with mixtures containing CF4, while still maintaining the very high, saturated gain, typical for these chambers. The overall improvement of TGC timing properties is such that 99% detection efficiency can be reached within a 20 ns gate.A simulation of the chamber timing properties using the measured drift velocities, reproduces well the measured data and can be used to predict chamber performance as a function of geometry and gas mixture. (C) 1998 Elsevier Science B.V. All rights reserved.