Search

The ATLAS experiment is getting ready to observe collisions between protons at a centre of mass energy of 14 TeV. These will be the highest energy collisions in a controlled environment to-date, to be provided by the Large Hadron Collider at CERN by mid 2008. The ATLAS Trigger and Data Acquisition (TDAQ) system selects events online in a three level trigger system in order to keep those events promising to unveil new physics at a budgeted rate of ~ 200 Hz for an event size of ~1.5 MB. This paper focuses on the data-logging system on the TDAQ side, the so-called 'Sub-Farm Output' (SFO) system. It takes data from the third level trigger, and it streams and indexes the events into different files, according to each event's trigger path. The data files are moved to CASTOR, the central mass storage facility at CERN. The final TDAQ data-logging system has been installed using 6 Linux PCs, holding in total 144 disks of 500 GB each, managed by three RAID controllers on each PC. The data-writing is managed in a controlled round-robin way among three independent filesystems associated to a distinct set of disks, managed by a distinct RAID controller. This novel design allows fast I/O, which together with a high speed network permits to minimize the number of SFO nodes. We report here on the functionality and performance requirements on the system, our experience with commissioning it and on the performance achieved. Index Terms--Data acquisition, data handling, disks.

The aim of the present work is the development of the hardware, firmware and software architecture of a Data Acquisition (DAQ) system suitable for the readout of high-speed high-resolution Silicon Drift Detectors and of Controlled-Drift Detectors for spectroscopic imaging of X-rays. The novelty of the developed DAQ system is to be sensitive to multiple pulses present in the sampled waveform without loss in measurement resolution with respect to a single pulse algorithm. This feature is particularly important at high event rates as it would improve the detected rate and also avoid errors in the pulse measurements. A multi-maximum search algorithm has been developed and implemented in order to demonstrate the feasibility of this approach. The focus of the paper is on the description of the general architecture and on the full test of the DAQ chain in experimental conditions. The resolution of the measured amplitude and time-of-arrival has been evaluated in the case of two pulses per waveform, including the case of partially overlapping events. In the case of Poissonian occurrence of pulses we compared the main performance parameters of the developed multiple-pulse DAQ (case of n = 2 pulses) with respect to a single-pulse DAQ which confirmed the expected increase of the event throughput in good agreement with the theoretical expectations and showed no degradation of the measurement resolution. Index Terms--Data Acquisition, silicon drift detector, x-ray imaging, x-ray spectroscopy.

The CMS Preshower is a fine grain detector that comprises 4288 silicon sensors, each containing 32 strips. The raw data are transferred from the detector to the counting room via 1208 optical fibres. Each fibre carries a 600-byte data packet per event. The maximum average level-I trigger rate of 100 kHz results in a total data flow of ~72 GB/s from the Preshower. For the readout of the Preshower, 56 links to the CMS DAQ have been reserved, each having a bandwidth of 200 MB/s (2 kB/event). The total available downstream bandwidth of ~11 GB/s necessitates a reduction in the data volume by a factor of at least 7. A modular VME-based system is currently under development. The main objective of each VME board in this system is to acquire on-detector data from at least 22 optical links, perform on-line data reduction and pass the concentrated data to the CMS DAQ. The principle modules that the system is based on are being developed in collaboration with the TOTEM experiment. Index Terms--Data acquisition, field programmable gate arrays, optical communication.

A parallel prototype readout system that allows digitization and acquisition of 64 or more anode signals from a position sensitive photomultiplier tube (PSPMT) was developed for a miniature hand-held gamma camera. This acquisition system was developed to study the benefits of a digital readout system compared to charge multiplexed techniques such as resistive division. The system was developed using CAMAC instrumentation standard and controlled via a Macintosh Computer. Four 16-channel charge-to-digital conversion (QDC) CAMAC modules were used to digitize individual anode signals from the PSPMT. To maximize the data transfer rate, a list processor module was also added in the system. For acquisition and processing of the digitized data, we used Kmax software from SPARROW. The system provided 99.9% spatial linearity when inter-anode gain correction was applied to list-mode data. Much improved scintillation crystal separation in a flood histogram with 16:1 peak to valley ratio, and higher edge sensitivity was obtained compared to resistive charge multiplexing readout. Index Terms--CAMAC, data acquisition, digital-readout, gamma camera, lutetium oxyorthosilicate (LSO), position sensitive photomultiplier tube (PSPMT).

A straw tracking detector was proposed for the MECO experiment in order to measure the parameters of the helical trajectory of electrons emitted from stopped muon decays. The events of interest are expected to be embedded in an intense background of both energetic electrons and low-energy protons. A prototype of the proposed detector with its DAQ system was built, tested, and compared to a simulation. The results are reported in this paper. They provide the information required to improve the computer simulation of the MECO experiment, and in general, the design of any high-rate DAQ system that is required to efficiently select minimum ionizing tracks from an environment of highly ionizing particles. Index Terms--Data acquisition system, tracking detector, waveform ADC.

A single-ended to differential linear current driver has been designed and implemented in a 0.25 [micro]m CMOS technology. This full-custom cell is intended for analogue data transmission in large-scale High-Energy Physics (HEP) experiments in the future CERN's Large Hadron Collider (LHC). Intrinsic technology radiation tolerance and specific design methodologies qualify this device to operate over 10 years in the LHC high radiation environment. High linearity and low power-overhead are achieved through a local feedback input stage and a current push-poll output stage. Linearity error is less than 0.1% in the specified operating range and 1% in close to full-swing operation. Static, dynamic and noise performance have been proven to be stable after a total ionising dose of 20 Mrad (Si[O.sub.2]) and after accelerated annealing. Index Terms--CMOS analog integrated circuits, current measurement, data acquisition, driver circuits, radiation hardening.

The ATLAS collaboration at CERN operated a combined test beam (CTB) from May until November 2004. The prototype of ATLAS data acquisition system (DAQ) was used to integrate other subsystems into a common CTB setup. Data were collected synchronously from all the ATLAS detectors, which represented nine different detector technologies. Electronics and software of the first level trigger were used to trigger the setup. Event selection algorithms of the high level trigger were integrated with the system and were tested with real detector data. The possibility to operate a remote Event Filter farm synchronized with the ATLAS Trigger and Data Acquisition System (TDAQ) was also tested. Event data, as well as detector conditions data, were made available for offline analysis.

We show how commodity CPU, networking and memory components greatly simplify a sophisticated trigger system designed for the demanding environment of a high data rate hadron collider experiment operating at 2 x [10.sup.32] [cm.sup.-2][s.sup.-1]. The trigger system is based on an 8-fold way, 3-level architecture capable of processing over 22 million data channels at a crossing rate of 2.5 MHz with a mean value of 6 interactions per crossing. Although originally designed for a B-physics experiment at the Tevatron, the flexible and highly scalable nature of the design should also be relevant to other next generation hadron collider experiments such as those at the LHC. Index Terms--Data acquisition, elementary particles, real time systems.

This paper describes the development of the optical multiplexer board (OMB), also known as PreROD board, for the TileCal readout system in the ATLAS experiment. The aim of this board is to overcome the problems that may arise in the integrity of data due to radiation effects. The solution adopted has been to add redundancy to data transmission and so two optical fibers with the same data come out from the detector front end boards. The OMB has to decide in real time which fiber, eventually, carries data with no errors switching it to the output link connected to the read out driver (ROD) motherboard where data processing takes place. Besides, the board may be also used as a data injector for testing purposes of the ROD motherboard. The paper describes the design and tests of the first prototype, implemented as a 6U VME64x slave module, including both hardware aspects, focusing on signal integrity problems, and firmware aspects, dealing with the cyclic redundancy code algorithms used to check data consistency used to make the decision. Index Terms--Data acquisition, fault tolerance, field programmable gate arrays, integrated circuit radiation effects.

BTeV was a proposed high-energy physics (HEP) collider experiment designed for the study of B-physics and CP Violation at the Tevatron at Fermilab. BTeV included a large-scale, high-speed trigger and data acquisition (DAQ) system, reading data from the detector at 500 Gbyte/s and writing data to mass storage at a rate of 200 Mbyte/s. The design of the trigger/DAQ system was innovative while remaining realistic in terms of technical feasibility, schedule and cost. This paper will give an overview of the BTeV trigger/DAQ architecture, highlight some of the technical challenges, and describe the approach that was used to solve these challenges. Index Terms--Data acquisition, large-scale systems, real time systems, triggering.

The J-PARC facility, which will be ready in 2008, is being constructed to perform a number of experiments including nuclear physics, kaon decays and neutrino oscillation. The expected data acquisition rate ranges from 500 Hz to 10 kHz, which is significantly higher than those used in the existing small experiments at KEK. We have developed a new data acquisition system that can be used in a wide range of experiments at J-PARC. The system consists of a KEK-VME crate, a readout platform module and peripheral modules. The readout platform module is highly modularized, having four slots to install daughter cards for digitization and three PCI mezzanine card (PMC) slots for on-board data processing and other purposes. The performance of the platform module and a model setup of the data acquisition system are reported. Index Terms--Common platform, data acquisition, J-PARC, KEK-VME, PMC.

The Event Filter (EF) selection stage is a fundamental L component of the ATLAS Trigger and Data Acquisition architecture. Its primary function is the reduction of data flow and rate to values acceptable by the mass storage operations and by the subsequent offline data reconstruction and analysis steps. The computing instrument of the EF is organized as a set of independent subfarms, each connected to one output of the Event Builder (EB) switch fabric. Each subfarm comprises a number of processors analyzing several complete events in parallel. This paper describes the design of the ATLAS EF system, its deployment in the 2004 ATLAS combined test beam together with some examples of integrating selection and monitoring algorithms. Since the processing algorithms are not explicitly designed for EF but are adapted from the offline ones, special emphasis is reserved to system reliability and data security, in particular for the case of failures in the processing algorithms. Other key design elements have been system modularity and scalability. The EF shall be able to follow technology evolution and should allow for using additional processing resources possibly remotely located. Index Terms--Data acquisition, data processing, triggering.

A data-loading technique that jointly considers the effect of channel estimation and the property of encoded multimedia data in Orthogonal Frequency Division Multiplexing (OFDM) systems is presented. It is observed that OFDM sub-channels experience different average bit error rate (BER) due to channel estimation inaccuracy.

This paper focuses on enhancing feature selection (FS) performance on a classification data set. First, a novel FS criterion using the concept of Bayesian discriminant is introduced. The proposed criterion is able to measure the classification ability of a feature set (or, a combination of the weighted features) in a direct way. This guarantees excellent FS results. Second, FS is conducted by optimizing the newly derived criterion in a continuous space instead of by heuristically searching features in a discrete feature space. Using this optimizing strategy, FS efficiency can be significantly improved. In this study, the proposed supervised FS scheme is compared with other related methods on different classification problems in which the number of features ranges from 33 to over 12,000. The presented results are very promising and corroborate the contributions of this study. Index Terms--A posteriori probability, Bayesian discriminant (BD), feature selection (FS), Parzen window estimator.

In this paper, an approach for automatically clustering a data set into a number of fuzzy partitions with a simulated annealing using a Reversible Jump Markov Chain Monte Carlo algorithm is proposed. This is in contrast to the widely used fuzzy clustering scheme, the Fuzzy C-Means (FCM) algorithm, which requires the a priori knowledge of the number of clusters. The said approach performs the clustering by optimizing a cluster validity index, the Xie-Beni index. It makes use of the homogeneous Reversible Jump Markov Chain Monte Carlo (RJMCMC) kernel as the proposal so that the algorithm is able to jump between different dimensions, i.e., number of clusters, until the correct value is obtained. Different moves, like birth, death, split, merge, and update, are used for sampling a candidate state given the current state. The effectiveness of the proposed technique in optimizing the Xie-Beni index and thereby determining the appropriate clustering is demonstrated for both artificial and real-life data sets. In a part of the investigation, the utility of the fuzzy clustering scheme for classifying pixels in an IRS satellite image of Kolkata is studied. A technique for reducing the computation efforts in the case of satellite image data is incorporated. Index Terms--Pattern recognition, fuzzy clustering, cluster validity index, determining the number of clusters, Reversible Jump Markov Chain Monte Carlo, simulated annealing, remote sensing.

This paper presents an efficient framework for error-bounded compression of high-dimensional discrete-attribute data sets. Such data sets, which frequently arise in a wide variety of applications, pose some of the most significant challenges in data analysis. Subsampling and compression are two key technologies for analyzing these data sets. The proposed framework, PROXIMUS, provides a technique for reducing large data sets into a much smaller set of representative patterns, on which traditional (expensive) analysis algorithms can be applied with minimal loss of accuracy. We show desirable properties of PROXIMUS in terms of runtime, scalability to large data sets, and performance in terms of capability to represent data in a compact form and discovery and interpretation of interesting patterns. We also demonstrate sample applications of PROXIMUS in association rule mining and semantic classification of term-document matrices. Our experimental results on real data sets show that use of the compressed data for association rule mining provides excellent precision and recall values (above 90 percent) across a range of problem parameters while reducing the time required for analysis drastically. We also show excellent interpretability of the patterns discovered by PROXIMUS in the context of clustering and classification of terms and documents. In doing so, we establish PROXIMUS as a tool for both preprocessing data before applying computationally expensive algorithms and directly extracting correlated patterns. Index Terms--Clustering, classification, association rules, data mining, sparse, structured and very large systems, singular value decomposition.

A very compact 32-channel digital delay module has been designed to fit in a single VME 6 U unit. It is equipped with both VME and Fast Intercrate Readout (FAIR) interfaces. Furthermore, a local manual programmability was implemented to use the modulealso in a stand-alone mode. A variety of NIM and ECL output have been implemented. A special ECL input allows the selection of different output regimes. The thermal stabilization is controlled via a PLL based circuit. The main features of the module are the wide range for the delay and the width of the output pulse: from 25 ns up to 6400 as, in 25 ns steps; and the low jitter: values of the order of 27 ps (11 ppm) were measured in several bench tests. Index Terms--Data acquisition, data buses, digital control.

In this paper, simulation ('computer modeling') of the Trigger/data acquisition (DAQ) system of the ATLAS experiment at the LHC accelerator is discussed. The system will consist of a few thousand end nodes, which are interconnected by a large Ethernet network. The nodes will run various applications under the Linux operating system (OS). Predictions for the latency, throughput and queue development in various places have been obtained. Results are presented with respect to the application of traffic shaping to reduce the probability of possible frame loss (which may cause severe performance degradation). Index Terms--Data acquisition, discrete-event simulation, local area network, modeling, queuing analysis, traffic control.

The base-line design and implementation of the ATLAS DAQ DataFlow system is described. The main components of the DataFlow system, their interactions, bandwidths, and rates are discussed and performance measurements on a 10% scale prototype for the final ATLAS TDAQ DataFlow system are presented. This prototype is a combination of custom design components and of multithreaded software applications implemented in C++ and running in a Linux environment on commercially available PCs interconnected by a fully switched gigabit Ethernet network. Index Terms--Computer network performance, data acquisition (DAQ), data buses, field programmable gate arrays (FPGAs), flow control, message passing, network testing, networks, optical fiber communication, particle collisions, radiation detectors, software, triggering.

A Toroidal LHC ApparatuS (ATLAS) Trigger/Data Acquisition (TDAQ) system connects via 1600 Read-Out-Links (ROL) to the ATLAS subdetectors. Each Read-Out-Buffer (Robin) prototype attaches to 2 ROLs, buffers the incoming event data stream of 160 MB/s each, and provides samples upon request to the TDAQ system. We present the design of the PCI-based Robin module, which is built around a XILINX XV2V1500 field-programmable-gate-array, together with initial results from rapid prototyping studies. Index Terms--Data acquisition, field programmable gate arrays (FPGAs).

Data acquisition (DAQ) electronics are described for a system of high-rate cathode strip chambers (CSC) in the forward region of A Toroidal LHC ApparatuS (ATLAS) muon spectrometer. The system provides serial streams of control signals for switched capacitor array analog memories on the chambers and accepts a total of nearly 294 Gbit/s in serial raw data streams from 64 chambers in the design configuration. Processing of the data is done in two stages, leading to an output bandwidth of 2.56 Gbit/s. The architecture of the system is described, as are some important signal processing algorithms and hardware implementation details. Although designed for a specific application, the architecture is sufficiently general to be used in other contexts. Index Terms--Digital signal processors, particle tracking, real-time systems.

The MINOS long-baseline neutrino experiment consists of two detectors separated by 730 km. Both are equipped with identical data acquisition (DAQ) systems, based on continuous, dead time free readout. Data are read from the untriggered front-end electronics by VME single board computers and transferred across high-speed PCI data links for consolidation by data routing processors. An array of Linux computers selects events of interest using software-based trigger algorithms. We present the design of the DAQ system and report on experience gathered during early operation of the experiment. Index Terms--Data acquisition, data buses, computer networks, programming.

The DZERO experiment began RunII datataking operation at Fermilab in spring 2001. The physics program of the experiment requires the Level 3 data acquisition (DAQ) system system to handle average event sizes of 250 kilobytes at a rate of 1 kHz. The system routes and transfers event fragments of approximately 1-20 kilobytes from 63 VME crate sources to any of approximately 100 processing nodes. It is built upon a Cisco 6509 Ethernet switch, standard PCs, and commodity VME single board computers (SBCs). The system has been in full operation since spring 2002. Index Terms--Computer networks, data acquisition, monitoring, physics, triggering.

A PCI/iRMX-based front-end system is being designed to serve as data acquisition (DAQ) subsystem for the HT-7U superconducting tokamak. The diagnostic instruments are connected to four analog-to-digital converter (ADC) boards that are directly plugged into the peripheral component interconnect (PCI) bus of a personal computer (PC) running the iRMX real-time operating system. Each ADC board has eight channels. The sampling rate of each channel can be up to 125 K samples per second. The acquired data are directly transferred from the ADC board into the memory of the PC, and then transferred to servers through the network. As a testbed, one PCI/iRMX subsystem has been built and has acquired data from the existing HT-7 tokamak. The DAQ can easily support a wide range of pulse lengths, even matching extremely long pulse and steady-state operation. This paper describes the system design and performance evaluation in detail. Index Terms--Data acquisition (DAQ), distributed systems, real-time systems.

The NA60 experiment was designed to identify signatures of a new state of matter, the Quark Gluon Plasma, in heavy-ion collisions at the CERN Super Proton Synchroton. The apparatus is composed of four main detectors: a muon spectrometer (MS), a zero degree calorimeter (ZDC), a silicon vertex telescope (VT), and a silicon microstrip beam tracker (BT). The readout of the whole experiment is based on a PCI architecture. The basic unit is a general purpose PCI card, interfaced to the different subdetectors via custom mezzanine cards. This allowed us to successfully implement several completely different readout protocols (from the VME like protocol of the MS to the custom protocol of the pixel telescope). The system was fully tested with proton and ion beams, and several million events were collected in 2002 and 2003. This paper presents the readout architecture of NA60, with particular emphasis on the PCI layer common to all the subdetectors. Index Terms--Data acquisition, heavy ion physics, PCI architecture, readout electronics.

Since its introduction in the early 1980s, the VMEbus plays a leading role in the embedded computing, real-time control and data acquisition systems for high energy physics experiments. In more than 20 years, the original standard has undergone major improvements and new features have been added to physical and logical layers, yet retaining a backward compatibility to protect investments and products life. High-speed data transactions are one of the most important features of the protocol in many applications. In this paper, we focus on the performances of the multiplexed block transfer cycle, a 64-bit data burst transaction fully supported by well-established VME64 silicon interfaces and the majority of high-end modules on the market. We confronted VME with VME64x backplane behaviors in light-to-moderate bus loading scenarios. Test results obtained with a blend of VME64 and VME64x-compliant boards are presented and discussed together with the backplanes' impedance analysis carried out with time domain reflectometry techniques. The impact on the transfer bandwidth of different load topologies is also reviewed. Index Terms--Data buses, line impedance, time-domain reflectometry.

The Data Collection Experiment (DCE) of the scientific mission DAVID (DAta and Video Interactive Distribution) of the Italian Space Agency (ASI) will pioneer the use of the W-band for telecommunications experiments. In particular the collection of high volumes of data from remote or virtually remote sites will be achieved through the exploitation of a W-band link in a time window of a few minutes per satellite pass. The experiment will hence demonstrate the capability of the W-band channel to be used reliably for a telecommunication link. At the same time, the experiment will provide useful elements for the characterisation of the W-band channel, in order to be able to design properly future operational systems working at W-band.

The PHOBOS data acquisition system based on a RACEway switching network is described. Occupying a single VME crate, the system utilizes 22 PPC750 CPUs working in parallel to compress data from 135 168 silicon pad detectors, and an UltraSPARC VME host for event building and data storage. Lossless Huffman coding is used for compression; this reduces the event size fourfold. The two-host disk array is used to stage data before sending them over Gigabit Ethernet to the Relativistic Heavy Ion Collider (RHIC) central computing facility. All trigger and control logic is formed using universal programmable logic VME modules, which can be programmed in situ, even when the system is running. The event building and run control software is written using the ROOT framework. The slow control and configuration makes use of an Oracle database to store configuration and monitoring parameters. The system has been taking data from the PHOBOS experiment at RHIC since June 2000. The achieved data-taking rate is 280 events/s or 28 MB/s, with additional disk arrays it can potentially reach 80 MB/s. Index Terms--Data acquisition (DAQ) system, FPDP, Huffman compression, Mercury OS, multihost SCSI, parallel data processing, power PC, RACEway, VME.

Initial attitude acquisition by a modern star tracker is investigated here. Criteria for efficient organization of the on-board database are discussed with reference to a brightness-independent initial acquisition algorithm. Star catalog generation preprocessing is described, with emphasis on the identification of minimum star brightness for detection by a sensor based on a charge coupled device (CCD) photodetector. This is a crucial step for proper evaluation of the attainable sky coverage when selecting the stars to be included in the on-board catalog. Test results are also reported, both for reliability and accuracy, even if the former is considered to be the primary target. Probability of erroneous solution is 0.2% in the ease of single runs of the procedure, while attitude determination accuracy is in the order of 0.02[degrees]in the average for the computation of the inertial pointing of the boresight axis.

Wearable computing is a promising technology, but data entry remains a challenge. An approach to data entry is proposed that relies on a head-mounted digital camera to record characters drawn by hand gestures or by a pointer.