Large High Energy Physics Experiments Research Articles

Characterization of radiation damages on Silicon photomultipliers by X-rays up to 100 kGy

Silicon photomultipliers (SiPMs) are highly-sensitive photodetectors emerging as the technology of choice for many applications, including among the others, large high-energy physics experiments and detectors for space instruments, where they are often exposed to a large amount of radiation. In recent years, there has been an increasing interest in assessing the performance deterioration of such detectors after ionizing and non-ionizing radiation, such as protons, neutrons and X or gamma rays. It is therefore interesting to characterize the effect of irradiation on such Geiger-mode detectors, differentiating between the ionizing and non-ionizing energy-loss effects. Moreover, it is interesting to compare the radiation damage effects on several types of SiPMs, to assess the main phenomena and the deterioration mechanisms, aiming to a more radiation tolerant SiPM design.In this work we irradiated several types of SiPM structures, produced in FBK (Trento, Italy), with 40 keV X-rays, at several doses, up to 100 kGy (in silicon), performing both online measurements (after each irradiation step) and offline functional characterization, after one month of room temperature annealing. The SiPMs are made with many different technologies, in particular different layouts, junction polarities, internal structures and starting materials. We studied the variation in the reverse current–voltage curves, distinguishing the effects on multiplied and not-multiplied current components, the primary dark count rate, the correlated noise probabilities and photon detection efficiency. Comparing all the measurement results, knowing the internal structure and the fabrication processes, we were able to extract and distinguish different deterioration mechanisms, also supported by TCAD simulations on the different effects of ionizing radiation inside the microcells.

Characterization of Silicon Photomultipliers after proton irradiation up to [formula omitted

Silicon photomultipliers (SiPMs) are highly-sensitive photodetectors emerging as the technology of choice for many applications, including large high-energy physics experiments where they often are exposed to high radiation fluences. In recent years, there has been an increasing interest in assessing the performance deterioration of such detectors after the irradiation with proton or neutron, with different fluence levels.In this work, samples of different FBK SiPM technologies, made with different manufacturing technologies, were irradiated at the INFN-LNS facility (Italy) with protons reaching fluences up to about 1014 neq/cm2 (1 MeV neutron equivalent) and their performances were characterized in detail after about 30-days room temperature annealing. The results show a significant worsening of the primary noise (dark count rate) of the detectors, which increases with the irradiation fluence, whereas the other performance parameters like the micro-cell gain, the correlated noise probability and the photon detection efficiency do not show significant variations up to 1011 neq/cm2 at least. The breakdown voltage estimation after irradiation is another important aspect for a SiPM. In this contribution, we show several methods for its estimation and compare the results. We also introduced new methodologies to characterize the performance of the SiPMs when they present a very high level of noise, such as the estimation of the dark count rate based on the measured reverse current, the estimation of variations in the photon detection efficiency through the measurement of the responsivity, and the measurement of the correlated noise and the gain through the average charge in response to a pulsed light signal.Lastly, we also analyzed the spatial localization of the proton-induced defects inside the device, i.e. the defects that mostly contribute to the increase of the DCR of the device, through the emission microscopy (EMMI) technique. In particular, we analyzed the SiPMs at the single cell level, trying to identify and spatially localize the defects.

A Neural-Network-defined Gaussian Mixture Model for particle identification applied to the LHCb fixed-target programme

Particle identification in large high-energy physics experiments typically relies onclassifiers obtained by combining many experimental observables. Predicting the probability density function (pdf) of such classifiers in the multivariate space covering the relevant experimental features is usually challenging. The detailed simulation of the detector response from first principlescannot provide the reliability needed for the most precise physics measurements.Data-driven modelling is usually preferred, though sometimes limited by the available data size and different coverage of the feature space by the control channels. In this paper, we discuss a novel approach to the modelling of particleidentification classifiers using machine-learning techniques. The marginal pdf of the classifiers is described with a Gaussian Mixture Model, whose parameters are predicted by Multi Layer Perceptrons trained on calibration data. As a proof of principle, the method is applied to the data acquired by the LHCb experiment in its fixed-target configuration. The model is trained on a data sample of proton-neon collisions and applied to smaller data samples of proton-helium and proton-argon collisions collected at different centre-of-mass energies. The method is shown to perform better than a detailed simulation-based approach, to be fast and suitable to be applied to a large variety of use cases.

Cryogenic Electronics Development for High-Energy Physics: An Overview of Design Considerations, Benefits, and Unique Challenges

In the quest to study the fundamental nature of matter and the universe, high-energy physics (HEP) experiments often operate in extreme conditions that lie well outside the standard operating range of integrated circuits (ICs). Two prominent examples of such extreme environments are 1) the irradiation levels experienced at high luminosity colliders and 2) operation at cryogenic temperatures [1]. Cryogenic electronics is a broad term that encompasses circuits operating at temperatures below the standard operating limit (−55 °C in the case of military grade electronics), all of the way down to millikelvin, as in the case of superconducting circuits. Cryogenic circuits have a long history [2] and have found applications in a broad spectrum of applications, such as infrared focal plane arrays, positron emission tomography, and quantum science. While CMOS circuits have been reliably operated at deep-cryogenic temperatures (<; 4.2 K), this article focuses on applications down to liquid nitrogen (77 K) and provides an overview of the design considerations, benefits, and unique challenges pertaining to cryogenic CMOS ICs for large HEP experiments.

Using ATLAS@Home to Exploit Extra CPU from Busy Grid Sites

Grid computing typically provides most of the data processing resources for large high-energy physics experiments. However, typical grid sites are not fully utilized by regular workloads. To increase the CPU utilization of these grid sites, the ATLAS@Home volunteer computing framework can be used as a backfilling mechanism. Results show an extra 15–42% of CPU cycles can be exploited by backfilling grid sites running regular workloads, while the overall CPU utilization can remain over 0.9. Backfilling has no impact on the failure rate of the grid jobs, and the impact on the CPU efficiency of grid jobs varies from 0.02 to 0.11 depending on the configuration of the site. In addition, the throughput of backfill jobs in terms of CPU time per simulated event is the same as for resources dedicated to ATLAS@Home. This approach is sufficiently generic that it can easily be extended to other clusters.

Accelerator Science and Technology in Europe EuCARD 2012

Abstract Accelerator science and technology is one of a key enablers of the developments in the particle physics, photon physics, electronics and photonics, also applications in medicine and industry. The paper presents a digest of the research results in accelerators in Europe, shown during the third annual meeting of the EuCARD - European Coordination of Accelerator Research and Development. EuCARD concerns building of research infrastructure, including advanced photonic and electronic systems for servicing large high energy physics experiments. There are debated a few basic groups of such systems like: measurement - control networks of large extent, multichannel systems for metrological data acquisition, precision photonic networks for reference time distribution.

A Novel Temperature Monitoring Sensor for Gas-Based Detectors in Large HEP Experiments

Abstract Gaseous detectors are commonly used in HEP (High Energy Physics) experiments to reconstruct the track of elementary particles. They are often made by a very large number of chambers with relatively small individual volume, arranged in thick layers placed approximately all around the vertex of the experiment in order to detect elementary particles produced in any direction. The large volume of gas inside the detector must be monitored for many parameters as they can affect both the efficiency and the working life of the detector. The temperature of the gas inside the individual chambers is a critical parameter to be monitored, as it can both affect the efficiency of the detector and point out on-board electronic circuitry overheating. In this paper we propose a novel gas temperature sensing system based on optical fibre technology. The adopted technology is well suited to make distributed sensing systems with large number of sensors, it is immune to electromagnetic disturbances and it has adequate radiation hardness. A prototype of the basic sensor of the proposed system was tested at the experimental facility for Resistive Plate Chamber characterization available at the INFN laboratories in Frascati. Results are presented and discussed.

CMS OnlineWeb-Based Monitoring

Abstract For large international High Energy Physics experiments, modern web technologies make the online monitoring of detector status, data acquisition status, trigger rates, luminosity, etc., accessible for the collaborators anywhere and anytime. This helps the collaborating experts monitor the status of the experiment, identify the problems and improve data taking efficiency. We present the online Web-Based Monitoring project of the CMS experiment at the LHC at CERN.The data sources are relational databasesandvarious messaging systems. The projectprovidesavast amountof in-depth information including real-time data, historical trends and correlations in a user-friendly way.

High Throughput WAN Data Transfer with Hadoop-based Storage

Hadoop distributed file system (HDFS) is becoming more popular in recent years as a key building block of integrated grid storage solution in the field of scientific computing. Wide Area Network (WAN) data transfer is one of the important data operations for large high energy physics experiments to manage, share and process datasets of PetaBytes scale in a highly distributed grid computing environment. In this paper, we present the experience of high throughput WAN data transfer with HDFS-based Storage Element. Two protocols, GridFTP and fast data transfer (FDT), are used to characterize the network performance of WAN data transfer.

Frog: The fast & realistic OpenGL event displayer

FROG [1] [2] is a generic framework dedicated to visualisation of events in high energy physics experiment. It is suitable to any particular physics experiment or detector design. The code is light (< 3 MB) and fast (browsing time ~ 20 events per second for a large High Energy Physics experiment) and can run on various operating systems, as its object-oriented structure (C++) relies on the cross-platform OpenGL[3] and Glut [4] libraries. Moreover, Frog does not require installation of heavy third party libraries for the visualisation. This documents describes the features and principles of Frog version 1.106, its working scheme and numerous functionalities such as: 3D and 2D visualisation, graphical user interface, mouse interface, configuration files, production of pictures of various format, integration of personal objects, etc. Finally the application of FROG for physic experiment/environement, such as Gastof, CMS, ILD, Delphes will be presented for illustration.

The Pierre Auger Observatory offline software

The Pierre Auger Observatory aims to discover the nature and origins of the highest energy cosmic rays. The large number of physicists involved in the project and the diversity of simulation and reconstruction tasks pose a challenge for the offline analysis software, not unlike the challenges confronting software for very large high energy physics experiments. Previously we have reported on the design and implementation of a general purpose but relatively lightweight framework which allows collaborators to contribute algorithms and sequencing instructions to build up the variety of applications they require. In this report, we update the status of this work and describe some of the successes and difficulties encountered over the last few years of use. We explain the machinery used to manage user contributions, to organize the abundance of configuration files, to facilitate multi-format file handling, and to provide access to event and time-dependent detector information residing in various data sources. We also describe the testing procedures used to help maintain stability of the code in the face of a large number of contributions. Foundation classes will also be discussed, including a novel geometry package which allows manipulation of abstract geometrical objects independent of coordinate system choice.

A fast and versatile interlock system

Abstract In today’s large fusion or high energy physics experiments it is a common requirement to shut down a component quickly under certain conditions. These conditions can include a complex logic and timing as well as topologically distributed inputs. In addition, the shutdown should be as instantaneous as possible. The shutdown mechanism should be flexible enough to allow for the changing requirements of the daily experimental work. The paper presents an interlock system which meets these requirements. The system has a modular design consisting of an arbitrary number of identically distributed modules which are connected to a dedicated interlock bus. Each module monitors 10 analog signals for the up- or downward violation of a programmable threshold and triggers one or several programmable interlock signals with only the transmission line delay. Nevertheless, the configuration of these modules is done via software. This makes the system fast and flexible at the same time. The risk of a malfunction is minimized by redundancy and self-surveillance of the interlock bus.

RADIATION ISSUES IN THE NEW GENERATION OF HIGH ENERGY PHYSICS EXPERIMENTS

With the construction of the Large Hadron Collider at the European Center for Nuclear Research (CERN), the radiation levels at large High Energy Physics (HEP) experiments are significantly increased with respect to past experience. The approach the HEP community is using to ensure radiation tolerance of the electronics installed in these new generation experiments is described. Particular attention is devoted to developments that led to original work: the estimate of the SEU rate in the complex LHC radiation environment and the use of hardness by design techniques to achieve radiation hardness of ASICs in a commercial CMOS technology.

GEANT4 code for simulation of a germanium gamma-ray detector and its application to efficiency calibration

The GEANT4 software was developed by RD44, a world-wide collaboration of national institutes, laboratories and large High-Energy Physics experiments. GEANT4 is a public software package composed of tools which can be used to accurately simulate the passage of particles through matter. In this article, the first attempt to use GEANT4 to model a reverse electrode germanium detector (REGe), and to improve also its efficiency calibration procedure, is presented. A variance reduction algorithm based on a directional bias scheme is implemented into GEANT4 in order to accelerate the efficiency computations. A fast optimisation method to model the detector geometry using standard point sources is also presented and validated for point, Marinelli and air filter sources. The simulated full-energy peak efficiencies agreed with the measured values to within 1% between 36 and 1460 keV for these three counting geometries.

Past, present and future of data acquisition systems in high energy physics experiments

Data Acquisition (DAQ) systems for large high-energy physics (HEP) experiments in the eighties were designed to handle data rates of megabytes per second. The next generation of HEP experiments at CERN (European Laboratory for High Energy Physics), is being designed around the new Large Hadron Collider (LHC) project, and will have to cope with gigabyte-per-second data flows. As a consequence, LHC experiments will require challengingly new equipment for detector readout, event filtering, event building and storage. The Fastbus and VME-based tree architectures of the eighties run out of steam when applied to LHC's requirements. New concepts and architectures from the nineties have substituted rack-mounting backplane buses for high speed point-to-point links, abandoned centralized event building, and instead use switched networks and parallel architectures. Following these trends, and in the context of DAQ and trigger systems for LHC experiments, this paper summarizes the earlier architectures and presents the new concepts for DAQ.

Architecture of a distributed real-time system to control large high-energy physics experiments

The control of a large high energy physics experiment involves multiple domains with different requirements (some parts have to work in real time, some are safety critical, others have to be user-friendly). Usually these domains are engineered separately. In order to increase the operating efficiency and the reliability and maintainability of the system, Delphi project at CERN took a global approach in the design of the complete experiment control. This approach allowed for the interconnection of the various domains and led to a high degree of automation and an homogeneous interface to the full control system. This paper describes an architecture and a development framework that can handle the different and sometimes contradictory requirements of the different parts of the experiment's online system.

Parallel and distributed real-time systems: an introduction

In this Special Issue we collected nine contributions on Parallel and Distributed Real-Time Systems. Below, we overview all nine papers included, which deal with problems and challenges in this rapidly growing domain. The particular papers tackle different issues related to developing applications. The topics covered in the first two groups of papers vary from off-take-shelf components using CORBA, to scheduling mechanisms in parallel real-time systems and load balancing in this kind of systems, to real-time communication protocols based on multicasting and providing fault tolerance, as well as standard protocols, such as Resource ReSerVation Protocol (RSVP). Another group of papers deals with verification principles in an environment supporting a radio broadcast paradigm and with two most challenging application domains for real-time distributed systems: on-board embedded systems for satellites and control of large high-energy physics experiments. Finally, we make some predictions on the most important aspects of the research practice in the near future, which we believe will have focused on system architectures and the verification process.

The GEANT-CALOR interface and benchmark calculations of ZEUS test calorimeters

The simulation of large scale high energy physics experiments is based mainly on the GEANT package. In the current version 3.15 the simulation of hadronic interacting particles is based on GHEISHA or FLUKA. Both programs miss an accurate simulation of the interaction of low energetic neutrons ( E kin < 20 MeV) with the materials of the detector. The CALOR89 program package contains a low energetic neutron code. An interface between the CALOR program parts and the GEANT package has been developed. A comparison of simulations with ZEUS test beam measurements shows a good agreement of the energy resolution and the e/h-ratio.

From DST to publication

Program and data structures in the off-line analysis of large high energy physics experiments are discussed. The experiments require a high degree of modularity of the reconstruction and analysis programs, working on a hierarchy of datasets with full and reduced event data. Event generation and detector simulation by Monte Carlo methods play an important role in the analysis for the determination of the detector acceptance and resolution, and the estimation of background from known processes to new physics. Concepts for general data analysis software and new analysis techniques are discussed with respect to the special conditions of HEP experiments. Support of the interactive graphical presentation of data at all levels, from the event display to the statistical analysis of physics variables, is essential.

Software for FASTBUS

FASTBUS is an international standard high-speed bus system for data acquisition and processing. It is used by several large high-energy physics experiments. Mandatory bus protocols and programmable system features permit sophisticated configurations of embedded and external processors to operate coherently. The associated software should support: all defined modes of bus access, test facilities for hardware development, fault diagnosis for device and system debugging, automated configuration and initialisation of large systems, and distributed data collection and processing. An overview of the definition and design of FASTBUS software is presented. The need for and use of software engineering methods is outlined. Basic concepts are illustrated by examples at the bus and system levels, with emphasis on general purpose, experiment-independent software.