ATLAS Liquid Argon Calorimeter Research Articles

The ATLAS liquid argon calorimeters: Construction, integration, commissioning and performance from selected beam-test results

The ATLAS liquid argon calorimeter system consists of an electromagnetic barrel calorimeter and two end-caps comprising electromagnetic, hadronic and forward calorimeters. The construction of the full calorimeter system is completed since mid-2004. After construction in the home institutes, the modules have been integrated into wheels, and inserted into their respective cryostats. The readout electronics has also been installed and commissioned. Results of electrical and mechanical quality checks performed during module construction, integration into wheels, cold test of complete calorimeter systems before and after lowering into the ATLAS cavern are reported. Some performance results on response linearity, energy resolution, muon detection and timing resolution, all obtained from the extensive test-beam program done during the construction and integration, are shown. These results confirm that the detector will meet the required physics performance. Since 2006, a continuously increasing fraction of the detector is tested using cosmic muons, and some results obtained from these data are presented.

Electronics calibration board for the ATLAS liquid argon calorimeters

To calibrate the energy response of the ATLAS liquid argon calorimeter, an electronics calibration board has been designed; it delivers a signal whose shape is close to the calorimeter ionization current signal with amplitude up to 100 mA in 50 Ω with 16 bit dynamic range. The amplitude of this signal is designed to be uniform over all calorimeters channels, stable in time and with an integral linearity much better that the electronics readout. The various R&D phases and most of the difficulties met are discussed and illustrated by many measurements. The custom design circuits are described and the layout of the ATLAS calibration board presented. The procedure used to qualify the boards is explained and the performance obtained illustrated: a dynamic range up to 3 TeV in three energy scales with an integral linearity better than 0.1% in each of them, a response uniformity better than 0.2% and a stability better than 0.1%. The performance of the board is well within the ATLAS requirements. Finally, in situ measurements done on the ATLAS calorimeter are shown to validate these performances.

The ATLAS Liquid Argon Calorimeters: integration, installation and commissioning

The ATLAS liquid argon calorimeter system consists of an electromagnetic barrel calorimeter and two end-caps with electromagnetic, hadronic and forward calorimeters positioned in three cryostats. Since May 2006 the LAr barrel calorimeter records regular calibration runs and takes cosmic muon data together with tile hadronic calorimeter in the ATLAS cavern. The cosmic runs with end-cap calorimeters started in April 2007. First results of these combined runs are presented.

Design and implementation of the Front End Board for the readout of the ATLAS liquid argon calorimeters

The ATLAS detector has been designed for operation at CERN's Large Hadron Collider. ATLAS includes a complex system of liquid argoncalorimeters. The electronics for amplifying, shaping, sampling, pipelining,and digitizing the calorimeter signals is implemented on the Front End Boards (FEBs). This paper describes the design, implementation and production of the FEBs and presents measurement results from testing performed at several stages during the production process.

The High Voltage Feedthroughs for the ATLAS Liquid Argon Calorimeters

The purpose, design specifications, construction techniques, and testing methods are described for the high voltage feedthrough ports and filters of the ATLAS Liquid Argon calorimeters. These feedthroughs carry about 5000 high voltage wires from a room temperature environment (300 K) through the cryostat walls to the calorimeters cells (89 K) while maintaining the electrical and cryogenic integrity of the system. The feedthrough wiring and filters operate at a maximum high voltage of 2.5 kV without danger of degradation by corona discharges or radiation at the Large Hadron Collider.

The ATLAS Liquid Argon Calorimeters : Construction, Integration, Commissionning

The ATLAS liquid argon calorimeter system consists of an electromagnetic barrel calorimeter and two end-caps comprising electromagnetic, hadronic and forward calorimeters. The construction of the full calorimeter system is completed since mid-2004. After construction in the home institutes, the modules have been integrated into wheels, and inserted into their respective cryostats. Results of electrical and mechanical quality checks performed during module construction, integration into wheels, cold test of complete calorimeter systems before and after lowering into the ATLAS cavern are reported. Finally, some results obtained from the first commissionning data are presented.

The ATLAS liquid argon calorimeter: Construction, integration, commissioning and combined test beam results

The construction and the installation of the ATLAS liquid argon calorimeters are now completed. In this paper, we will briefly review the design of the calorimeters and describe the integration and installation steps. The result of the calorimeters’ commissioning on the surface and in the cavern, and the results of the combined test beam in 2004 are also shown.

Signal feedthroughs for the ATLAS barrel and endcap calorimeters

The function, design, construction, testing, and installation of the signal feedthroughs for the barrel and endcap ATLAS liquid argon calorimeters are described. The feedthroughs provide a high density and radiation hard method to extract over 200 000 signals from the cryogenic environment of the calorimeters using an application of a design based on flexible kapton circuit board transmission lines. A model to describe the frequency dependent behavior of the transmission lines is also presented.

The ATLAS liquid argon calorimeter—status and expected performance

For the ATLAS detector at the LHC, the liquid argon technique is exploited for the electromagnetic calorimetry in the central part and for the electromagnetic and hadronic calorimetry in the forward and backward regions. The construction of the calorimeter is well advanced with full cold tests of the barrel calorimeter and first endcap calorimeter only months away. The status of the project is discussed as well as the related results from beam test studies of the various calorimeter subdetectors. The results show that the expected performance meets the ATLAS requirements as specified in the ATLAS Technical Design Report.

The ATLAS liquid argon calorimeter—status and expected performance

For the ATLAS detector at the LHC, the liquid argon technique is exploited for the electromagnetic calorimetry in the central part and for the electromagnetic and hadronic calorimetry in the forward and backward regions. The construction of the calorimeter is well advanced with full cold tests of the barrel calorimeter and first endcap calorimeter only months away. The status of the project is discussed as well as the related results from beam test studies of the various calorimeter subdetectors. The results show that the expected performance meets the ATLAS requirements as specified in the ATLAS Technical Design Report.

Pollution of liquid argon after neutron irradiation

The purpose of the neutron facility installed at SARA is to investigate the behavior of various materials to be used in the ATLAS liquid argon calorimeter, when submitted to fast neutron radiation. The samples are placed in a liquid argon cryostat a few cm away from the neutron source. Various pieces of the electromagnetic calorimeter have been tested in order to evaluate the rate of pollution of the liquid and consequently the possible signal loss in energy measurements. The average fluence was equivalent to the maximum expected in the calorimeter in about 10 years. The most striking feature of the results is that the pollution is not due to oxygen, at least for most of it. Using a particular value of the absorption length derived from these data, a simulation was carried out and the energy signal loss in the calorimeter could be predicted. Within the limits of our present knowledge, the conclusion is that damages due to this pollution will not be a problem.

The readout driver (ROD) for the ATLAS liquid argon calorimeters

The Readout Driver (ROD) for the Liquid Argon calorimeter of the ATLAS detector is described. Each ROD module receives triggered data from 256 calorimeter cells via two fiber-optics 1.28 Gbit/s links with a 100 kHz event rate (25 kbit/event). Its principal function is to determine the precise energy and timing of the signal from discrete samples of the waveform, taken each period of the LHC clock (25 ns). In addition, it checks, histograms, and formats the digital data stream. A demonstrator system, consisting of a motherboard and several daughter-board processing units (PUs) was constructed and is currently used for tests in the lab. The design of this prototype board is presented here. The board offers maximum modularity and allows the development and testing of different PU designs based on today's leading integer and floating point DSPs.

Irradiation studies of Gb/s optical links developed for the front-end read-out of the ATLAS liquid argon calorimeter

In the baseline read-out scheme of the ATLAS liquid argon calorimeter, approximately 1500 unidirectional Gigavit/s (Gb/s) optical links are used to transfer data from teh calorimeter to receivers in data acquisition electronics situated up to 200 metres away. In the architecture of the link currently under development, VCSEL's (Vertical Cavity Surface Emitting Laser diodes) mounted on-detector are coupled to PIN-photodiodes located in receivers through graded-index multimode optical fibres. Over 10 years of ATLAS running, the components of the emitter will be exposed to high levels of neutron (1.7 × 10 13 n (1MeV Si) cm −2) and gamma (800 Gy) radiation. Their performance has been explored using neutron and gamma facilities and the results of these studies are presented in this paper. No significant levels of radiation are expected for the receiving part of the link.

Neutron and gamma irradiation studies of packaged VCSEL emitters for the optical read-out of the ATLAS electromagnetic calorimeter

Vertical cavity surface emitting laser diodes (VCSELs) are being investigated for use in the on-detector transmitters of the ATLAS liquid argon calorimeter optical read-out links. The radiation tolerance of optical components mounted on-detector is a critical concern. Packaged VCSEL emitters from Honeywell and Mitel have been irradiated with neutrons up to ( 2.1±0.4)×10 13 n (1 MeV equivalent in Si) cm −2 and gammas up to (5.1±0.2) kGy. The packaged components were mounted in ‘ST’ style fibre receptacles and monitored through-out the irradiation. A radiation-induced attenuation of 10–15% was seen after neutron irradiation. The induced attenuation after the gamma irradiation was <5%. The threshold current did not change in either case. An annealing current of between 5 and 8 mA restored the light output levels to pre-irradiation levels after approximately 12 h for the neutron irradiated devices. The gamma irradiated devices exhibited no such behaviour.

Hadronic endcap calorimetry at ATLAS and results from the first prototype

The physics constraints on the design of the calorimeter are briefly discussed. A description of the mechanical design and the readout system for the ATLAS Liquid Argon Hadronic End-cap Calorimeters (HEC) is presented. Finally, preliminary results from tests of the first prototypes of the HEC are reported.

Status and future plans of the canadian ATLAS Collaboration

The Canadian ATLAS collaboration has assumed responsibility for the construction of key elements of the ATLAS liquid argon calorimeter system. The group will construct parts of the hadronic endcap calorimeter, the forward calorimeter, and the calorimeter readout electronics. Canadians are also leading in the areas of radiation damage studies and optimization of the endcap region. Physics simulation studies in Canada have concentrated on searches for heavy Higgs particles using reconstructed jets in the endcap calorimeters.