Liquid Argon Calorimeter Research Articles

A Serializer ASIC at 5 Gbps for Detector Front-end Electronics Readout

Optical data links are used in detector front-end electronics readout systems of experiments in the Tevatron and the LHC. Optical links in high energy particle physics experiments usually have special requirements such as radiation tolerance, ultra high reliability and low power dissipation. These requirements are often not met by commercial components which are designed for applications in non-radiation, accessible (for maintenance) environment, and for multi-vendor systems so the parts must comply with certain standards. Future HEP experiments such as the upgrades for the sLHC call for optical links with ultra high data bandwidth, higher radiation tolerance and ultra low power dissipation. To meet these challenges and in particular those in the upgrade for the ATLAS Liquid Argon Calorimeter readout that calls for an optical link system of 100 Gbps for each front-end board, we adopted a full custom front-end electronics system design based on application specific integrated circuits. Reported here are the development and test results of two circuits: a 5 Gbps serializer and a 5 GHz phase locked loop, and a block diagram design for the 100 Gbps optical link.

A novel calorimeter trigger concept: The jet trigger of the H1 experiment at HERA

We report on a novel trigger for the liquid argon calorimeter which was installed in the H1 Experiment at HERA. This trigger, called the “Jet Trigger”, was running at level 1 and implemented a real-time cluster algorithm. Within only 800 ns, the Jet Trigger algorithm found local energy maxima in the calorimeter, summed their immediate neighbors, sorted the resulting jets by energy, and applied topological conditions for the final level 1 trigger decision. The Jet Trigger was in operation from the year 2006 until the end of the HERA running in the summer of 2007. With the Jet Trigger it was possible to substantially reduce the thresholds for triggering on electrons and jets, giving access to a largely extended phase space for physical observables which could not have been reached in H1 before. The concepts of the Jet Trigger may be an interesting upgrade option for the LHC experiments.

Optical links for ATLAS liquid argon calorimeter front-end electronics readout

We present the optical data links for the ATLAS liquid argon calorimeter. The current status of the vertical cavity surface emitting laser failures, the up-to-date results in searching for the failure cause, experiences gained in the searching process, possible backup plans for the optical transmitters and the lessons learned are also discussed.

A readout driver for the ATLAS LAr-calorimeter at a High Luminosity LHC

A new readout driver (ROD) is being developed as a central part of the signal processing of the ATLAS liquid-argon calorimeters for operation at the High Luminosity LHC (HL-LHC). In the architecture of the upgraded readout system, the ROD modules will have several challenging tasks: receiving of up to 1.4 Tb/s of data per board from the detector front-end on multiple high-speed serial links, low-latency data processing, data buffering, and data transmission to the ATLAS trigger and DAQ systems. In order to evaluate the different components, prototype boards in ATCA format equipped with modern Xilinx and Altera FPGAs have been built. We will report on the measured performance of the SERDES devices, the parallel signal processing using DSP slices, the implementation of trigger interfaces, using e.g. multi-Gb Ethernet, as well as the development of the ATCA infrastructure on the very first ROD prototype modules.

Combined performance studies for electrons at the 2004 ATLAS combined test-beam

In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Radiation Tracker, Bremsstrahlungs-recovery algorithms relying on the LAr calorimeter and results obtained for the E/p ratio and a way how to extract scale parameters will be discussed.

Performance of the electronic readout of the ATLAS liquid argon calorimeters

The ATLAS detector has been designed for operation at the Large Hadron Collider at CERN. ATLAS includes electromagnetic and hadronic liquid argon calorimeters, with almost 200,000 channels of data that must be sampled at the LHC bunch crossing frequency of 40 MHz. The calorimeter electronics calibration and readout are performed by custom electronics developed specifically for these purposes. This paper describes the system performance of the ATLAS liquid argon calibration and readout electronics, including noise, energy and time resolution, and long term stability, with data taken mainly from full-system calibration runs performed after installation of the system in the ATLAS detector hall at CERN.

Readiness of the ATLAS liquid argon calorimeter for LHC collisions

The ATLAS liquid argon calorimeter has been operating continuously since August 2006. At this time, only part of the calorimeter was readout, but since the beginning of 2008, all calorimeter cells have been connected to the ATLAS readout system in preparation for LHC collisions. This paper gives an overview of the liquid argon calorimeter performance measured in situ with random triggers, calibration data, cosmic muons, and LHC beam splash events. Results on the detector operation, timing performance, electronics noise, and gain stability are presented. High energy deposits from radiative cosmic muons and beam splash events allow to check the intrinsic constant term of the energy resolution. The uniformity of the electromagnetic barrel calorimeter response along η (averaged over φ) is measured at the percent level using minimum ionizing cosmic muons. Finally, studies of electromagnetic showers from radiative muons have been used to cross-check the Monte Carlo simulation. The performance results obtained using the ATLAS readout, data acquisition, and reconstruction software indicate that the liquid argon calorimeter is well-prepared for collisions at the dawn of the LHC era.

The ATLAS liquid argon calorimeter at the LHC

The Liquid Argon (LAr) calorimeter is a key detector component in the ATLAS experiment at the LHC. It has been installed in the ATLAS cavern and is filled with liquid argon since 2006. Its performance has been studied using random triggers, calibration data, cosmic muons (from September–October 2008 and June–July 2009 cosmic data taking), LHC beam splash events (from September 2008 and November 2009 LHC running), and collision events (from November and December 2009 LHC running). The properties of each read-out channel such as pedestal, noise and gain have been measured and the high stability of the LAr electronics over several months of data taking is shown. Calibration data are stored into a database and used at reconstruction level (online and offline). The quality of the energy reconstruction at the first trigger level has also been studied. The method used to predict the ionization pulse shape is presented and the prediction is compared to ionization signals from cosmic muons. The uniformity of the calorimeter response has also been measured. Splash events have been used to estimate the calorimeter timing. Moreover, the missing transverse energy resolution has been evaluated using collision events and compared to the expected resolution.

The ATLAS LAr Calorimeter Level 1 Trigger Signal Pre-Processing System: Installation, Commissioning and Calibration Results

We describe the ATLAS Liquid Argon calorimeter (LAr) electronics used to prepare signals for the L1 trigger, studied with a standalone data acquisition system built for the commissioning of the LAr-L1 electronics. This includes calibration data used to extract gains of all LAr calorimeters and timing shifts for different layers of the electromagnetic (EM) calorimeter. Analysis tools have been developed to study the pulse shape, timing, and amplitude, which are employed for the readout of signals from both the main detector and the L1 branch. Performance studies using beam data is also shown.

R&D studies of the ATLAS LAr calorimeter readout electronics for super-LHC

The ATLAS Liquid Argon (LAr) calorimeters are high precision, high sensitivity and high granularity detectors. A total of 182,468 signals are digitized and processed real-time on detector, to provide energy and time deposited in each detector element at every occurrence of the L1-trigger. The current readout electronics will need to be upgraded to sustain the higher radiation levels expected with the increase of a factor 10 in luminosity at the LHC in the years ∼2017. A completely innovative readout scheme is being developed. The front-end readout will send out data continuously at each bunch crossing through high speed radiation resistant optical links, the data will be processed real-time with the possibility of implementing trigger algorithms.This article is an overview of the R&D activities and architectural studies the ATLAS LAr Calorimeter Group is developing: front-end analog and mixed-signal ASIC design, radiation resistance optical-links in SOS, high-speed back-end processing units based on FPGA architectures and power supply distribution schemes.

Performance of the ATLAS liquid argon calorimeter with cosmic muons and single LHC beam data

The Liquid Argon (LAr) calorimeter is a key detector in the ATLAS (A Toroidal LHC ApparatuS) experiment at the Large Hadron Collider (LHC), designed to provide precision measurements of electrons, photons, jets and missing transverse energy. Cosmic muon data has been recorded by the LAr calorimeter at various stages of commissioning, with the first single LHC beam data being recorded in September 2008. We present here the LAr calorimeter performance studies based on cosmic muons and LHC beam data. In 2008, ∼99% of the LAr readout channels were fully operational. The high energy deposits in the calorimeter readout cells have been used to validate the signal shape reconstruction from calibration predictions at a level better than ∼2%. The measured timing alignment agrees with expectations at the 2ns level. The non-uniformity of the barrel electromagnetic (EM) calorimeter has been estimated less than 2% thanks to cosmic muons.

Electronic calibration of the ATLAS LAr calorimeter

The Liquid Argon (LAr) calorimeter is a key detector component in the ATLAS experiment at the LHC, designed to provide precision measurements of electrons, photons, jets and missing transverse energy. A critical element in the precision measurement is the electronic calibration. In this article, the computation of the energy deposited in a cell is presented as well as the role of the different calibration constants, revealing the complex calibration scheme which has been put in place. Since the installation of the LAr calorimeter in the ATLAS cavern, the electronic calibration of the readout system has been continuously exercised in the commissioning phase. The large amount of collected calibration data allows careful studies of the stability of constants, like pedestals and pulse shapes. Thanks to the experience gained during the last two years, a calibration procedure has been put in place for the LHC running period.

The Atlas Liquid Argon Calorimeter: Commissioning with Cosmic Muons and First LHC Beams

In 2009, the Large Hadron Collider at CERN will collide protons with a center of mass energy of 14 TeV. ATLAS is a general purpose experiment that will allow to explore the wide potential of discovery and achieve high precision measurements. The ATLAS liquid argon calorimeters are presented, with an emphasis on their in situ commissioning using cosmic muons and their response during the first LHC single beam runs on September 2008.

Operation of the ATLAS end-cap calorimeters at sLHC luminosities: An experimental study

The expected increase of luminosity at sLHC by a factor of ten with respect to LHC luminosities has serious consequences for the ATLAS liquid argon calorimeters in the end-cap (EMEC, HEC) and in the forward region (FCAL). Small modules of each type of calorimeter have been built and exposed to a high intensity (up to 10 12 pps) proton beam of 60 GeV at IHEP/Protvino. The correlation between beam intensity and the read-out signal has been studied. Also, the dependence of the HV currents as well as calorimeter module temperature on the beam intensity has been measured.

Commissioning of the ATLAS liquid argon calorimeter

The in situ commissioning of the ATLAS liquid argon calorimeter is taking place since three years. During this period, it has been fully tested by means of frequent calibration runs, and the analysis of the large cosmic muon data samples and of the few beam splash events that occurred on September 10th, 2008. This has allowed to obtain a stable set of calibration constants for the first collisions, and to measure the in situ calorimeter performances that were found to be at the expected level.

Evaluation of silicon-germanium (SiGe) bipolar technologies for use in an upgraded atlas detector

Silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) technologies promise several advantages over CMOS for the front-end readout electronics for the ATLAS upgrade. We have evaluated the relative merits of the latest generations of IBM SiGe HBT BiCMOS technologies, the 8WL and 8HP platforms. These 130 nm SiGe technologies show promise to operate at lower power than do CMOS technologies and would provide a viable alternative for the silicon strip detector and liquid argon calorimeter upgrades, provided that the radiation tolerance studies at multiple gamma and neutron irradiation levels, included in this investigation, show them to be sufficiently radiation tolerant.

Electronic calibration of the ATLAS LAr calorimeter and commissioning with cosmic muon signals

The three cryostats of the Liquid Argon calorimeter System have been gradually installed at their nominal position in the ATLAS cavern from end 2005 to beginning of 2008. After the cabling and installation, calibration runs are taken routinely, allowing to set-up and debug the electronics. Finally cosmic muon runs are also recorded regularly since august 2006 to test in situ the signal reconstruction procedure used to obtain the energy in each cell, as well as to check some of the detector performance. This paper presents the current status of these analyses.

Performance of the ATLAS forward calorimeter

The ATLAS forward calorimeter is a liquid argon calorimeter based on a novel tubular electrode structure. This paper will focus on the performance of the calorimeter for electrons and hadrons, based on the analysis of beam test data taken in the H6 beamline at CERN in 2003. The ATLAS requirements on the forward calorimeter performance will be reviewed, the calorimeter design and construction will be discussed, and the performance for electron and hadrons will be described.

Radiation qualification of the front-end electronics for the readout of the ATLAS liquid argon calorimeters

The ATLAS detector has been built to study the reactions produced by theLarge Hadron Collider (LHC). ATLAS includes a system of liquid argon calorimeters for energymeasurements. The electronics for amplifying, shaping, sampling, pipelining, anddigitizing the calorimeter signals is implemented on a set of front-endelectronic boards. The front-end boards are installed in crates mounted between thecalorimeters, where they will be subjected to significant levels ofradiation during LHC operation. As a result, all components used on the front-end boards had to besubjected to an extensive set of radiation qualification tests.This paper describes radiation-tolerant designs, radiation testing, andradiation qualification of the front-end readout system for the ATLASliquid argon calorimeters.

ATLAS liquid argon calorimeter front end electronics

The ATLAS detector has been designed for operation at CERN's Large Hadron Collider. ATLAS includes a complex system of liquid argoncalorimeters. This paper describes the architecture and implementationof the system of custom front end electronics developed for the readout of the ATLAS liquid argon calorimeters.