Showing papers in "Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment in 2006"

Geiger-mode avalanche photodiodes, history, properties and problems

Abstract: Geiger-mode avalanche photodiodes (G-APDs) have been developed during recent years and promise to be an alternative to photomultiplier tubes. They have many advantages like single photon response, high detection efficiency, high gain at low bias voltage and very good timing properties but some of their properties, the dark count rate for example, can be a problem. Several types of G-APDs are on the market and should be selected carefully for a given application.

Micromegas in a bulk

Abstract: In this paper, we present a novel way to manufacture the bulk Micromegas detector. A simple process based on the Printed Circuit Board (PCB) technology is employed to produce the entire sensitive detector. Such a fabrication process could be extended to very large area detectors made by the industry. The low cost fabrication together with the robustness of the electrode materials will make it attractive for several applications ranging from particle physics and astrophysics to medicine.

The upgraded DØ detector

Abstract: The D0 experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to D0.

Status report on silicon photomultiplier development and its applications

Abstract: The state of art of the Silicon Photomultipliers (SiPM’s)—their features, possibilities and applications—is given. The significant progress of this novel technique of photo detection is described and discussed. r 2006 Elsevier B.V. All rights reserved.

The NeuroBayes neural network package

Abstract: Detailed analysis of correlated data plays a vital role in modern analyses. We present a sophisticated neural network package based on Bayesian statistics which can be used for both classification and event-by-event prediction of the complete probability density distribution for continuous quantities. The network provides numerous possibilities to automatically preprocess the input variables and uses advanced regularisation and pruning techniques to essentially eliminate the risk of overtraining. Examples from physics and industry are given.

The FEI3 readout chip for the ATLAS pixel detector

Abstract: The latest pixel readout chip FEI3 for the ATLAS detector has been implemented in a standard 0.25 μ m CMOS process using radiation tolerant layout rules. It contains 2880 readout channels with densely packed analogue and digital circuits, a novel analogue front end and a complex time stamp based readout architecture and meets all specifications. Radiation tolerance has been demonstrated up to 100 Mrad of total dose. This paper summarizes the overall chip architecture and describes the most important circuit elements in some detail.

COSY INFINITY Version 9

Abstract: In this paper, we review the features in the newly released version of COSY INFINITY, which currently has a base of more than 1000 registered users, focusing on the topics which are new and some topics which became available after the first release of the previous versions 8 and 8.1. The recent main enhancements of the code are devoted to reliability and efficiency of the computation, to verified integration, and to rigorous global optimization. There are various data types available in COSY INFINITY to support these goals, and the paper also reviews the feature and usage of those data types.

The Los Alamos Neutron Science Center

Abstract: The Los Alamos Neutron Science Center, or LANSCE, uses the first truly high-current medium-energy proton linear accelerator, which operated originally at a beam power of 1 MW for medium-energy nuclear physics. Today LANSCE continues operation as one of the most versatile accelerator-based user facilities in the world. During eight months of annual operation, scientists from around the world work at LANSCE to execute an extraordinarily broad program of defense and civilian research. Several areas operate simultaneously. The Lujan Neutron Scattering Center (Lujan Center) is a moderated spallation source (meV to keV), the Weapons Neutron Research Facility (WNR) is a bare spallation neutron source (keV to 800 MeV), and a new ultra-cold neutron source will be operational in 2005. These sources give LANSCE the ability to produce and use neutrons with energies that range over 14 orders of magnitude. LANSCE also supplies beam to WNR and two other areas for applications requiring protons. In a proton radiography (pRad) area, a sequence of narrow proton pulses is transmitted through shocked materials and imaged to study dynamic properties. In 2005, LANSCE began operating a facility that uses 100-MeV protons to produce medical radioisotopes. To sustain a vigorous program beyond this decade, LANSCE has embarked on a project to refurbish key elements of the facility and to plan capabilities beyond those that presently exist.

Advances in Thick GEM-like gaseous electron multipliers—Part I: atmospheric pressure operation

Abstract: Thick GEM-like (THGEM) gaseous electron multipliers are made of standard printed-circuit board perforated with sub-millimeter diameter holes, etched at their rims. Effective gas multiplication factors of 10 5 and 10 7 and fast pulses in the few nanosecond rise-time scale were reached in single- and cascaded double-THGEM elements, in atmospheric-pressure standard gas mixtures with single photoelectrons. High single-electron detection efficiency is obtained in photon detectors combining THGEMs and semitransparent UVsensitive CsI photocathodes or reflective ones deposited on the top THGEM face; the latter benefits of a reduced sensitivity to ionizing background radiation. Stable operation was recorded with photoelectron fluxes exceeding MHz/mm 2 . The properties and some potential applications of these simple and robust multipliers are discussed.

New materials for radiation hard semiconductor dectectors

Abstract: On behalf of the RD50 collaboration Abstract We present a review of the current status of research into new semiconductor materials for use as particle tracking detectors in very high radiation environments. This work is carried out within the framework of the CERN RD50 collaboration, which is investigating detector technologies suitable for operation at the proposed Super-LHC facility (SLHC). Tracking detectors operating at the SLHC in this environment will have to be capable of withstanding radiation levels arising from a luminosity of 10 35 cm -2 s -1 which will present severe challenges to current tracking detector technologies. The "new materials" activity within RD50 is investigating the performance of various semiconductor materials that potentially offer radiation hard alternatives to silicon devices. The main contenders in this study are silicon carbide, gallium nitride and amorphous silicon. In this paper we review the current status of these materials, in terms of material quality, commercial availability, charge transport properties, and radiation hardness studies. Whilst these materials currently show considerable promise for use as radiation hard tracking detectors, their ultimate success will depend on the continued improvement of the availability of high quality material.

Data acquisition and processing software package for Medipix2

Abstract: The semiconductor pixel detector Medipix2 [1] (256×256 square pixels, 55×55 μm2 each) is a superior imaging device in terms of spatial resolution, linearity and dynamic range. This makes it suitable for various applications such as radiography, neutronography, and micro–tomography. The software package for acquisition and data processing has been developed to control and manage complex measurements. The solution features an open and very flexible modular architecture with custom made plugin support. Plugins can control parts of the acquisition system as well as perform real-time data processing and use these results as feedback for controlling further steps of measurements. This allows us to control, e.g. data acquisition, position and rotation of the sample (stepper motors), source parameters, temperature, etc. in a synchronized way. An example is the adaptive tomography plugin which adaptively controls the measurement and benefits from preprocessing performed by other plugins such as the beam-hardening correction of measured projections.

Layout and performance of RPCs used in the Argo-YBJ experiment

Abstract: The layout of the RPCs, used in the Argo-YBJ experiment to image with a high space-time granularity the atmospheric shower, is described in this paper. The detector has been assembled to provide both digital and analog informations in order to cover a wide particle density range with a time accuracy of 1 ns. The experimental results obtained operating the chambers in streamer mode at sea level with a standard gas mixture are presented.

Determination of the jet energy scale at the collider detector at Fermilab

Abstract: A precise determination of the energy scale of jets at the Collider Detector at Fermilab at the Tevatron p p ¯ collider is described. Jets are used in many analyses to estimate the energies of partons resulting from the underlying physics process. Several correction factors are developed to estimate the original parton energy from the observed jet energy in the calorimeter. The jet energy response is compared between data and Monte Carlo simulation for various physics processes, and systematic uncertainties on the jet energy scale are determined. For jets with transverse momenta above 50 GeV the jet energy scale is determined with a 3 % systematic uncertainty.

The barrel modules of the ATLAS semiconductor tracker

Abstract: This paper describes the silicon microstrip modules in the barrel section of the SemiConductor Tracker (SCT) of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The module requirements, components and assembly techniques are given, as well as first results of the module performance on the fully assembled barrels that make up the detector being installed in the ATLAS experiment.

The OPERA film: New nuclear emulsion for large-scale, high-precision experiments

Abstract: Industrial mass production of nuclear emulsion film has been realized by the introduction of new photographic technologies. In addition, emulsion-refreshing capability (erasing unwanted tracks before its use) was implemented by controlling the fading characteristics of the gel. The gel properties were optimized in order to satisfy this requirement; rapid track erasing at the erasing condition and minimum fading during the running of experiments. Emulsion films with this capability are crucial for large-scale applications like the long base-line neutrino experiment, OPERA, which intend to detect Tau neutrino appearance at 732 km from the beam source.

USB interface for Medipix2 pixel device enabling energy and position-sensitive detection of heavy charged particles

Abstract: We have designed an interface board between the Medipix2 single photon counting chip and Universal Serial Bus (USB), which is presently the most widespread PC interface. All necessary detector support is integrated into one compact system ( 80 × 50 × 20 mm 3 ) including the detector bias source (up to 100 V). Power supply is internally derived from the voltage provided by the USB connection, so no external device is required. This solution allows to achieve maximum portability of the measurement setup. One of the most significant advantages is the support of back-side pulse processing. The charge generated by an ionizing particle is measured in the bias circuit and can be used for spectroscopic purposes or for triggering. With the present design, the energy resolution of such spectrometry is about 44 keV.The interface board has been designed for connection with present chip-boards carrying one or four Medipix2 chips.

A method to improve tracking and particle identification in TPCs and silicon detectors

Abstract: The measurement of the ionization by charged particles in a medium (gas or condensed) together with the measurement of their momentum or energy is used for tracking the particles and to determine their identity. For tracking the lateral extent of the ionization cloud should be known. For tracking and for charged particle identification (PID), one must understand that energy loss of particles, ionization and detector output are related, but not identical. In this paper, I discuss the relevant physics processes involved in PID and tracking and the stochastic nature of the energy loss mechanism. These calculations can be made with analytic and Monte Carlo methods. The expression dE/dx should be abandoned; it is never relevant to the signals in a particle-by-particle analysis. Specific terms such as energy loss, energy deposition, ionization and pulse height should be used instead. It is important that an accurate data analysis requires attention to track segmentation. I will show that properties of straggling functions for gases and thin silicon detectors are similar for equivalent absorber thicknesses and general conclusions given for one absorber will be valid for others. Thus, these techniques can be used in Time Projection Chambers (TPCs) and Silicon Drift Detectors. I will show how to use this formalism in the STAR and ALICE TPCs and describe how its use has improved the performance of the detector.

Software alignment for tracking detectors

Abstract: Tracking detectors in high-energy physics experiments require an accurate determination of a large number of alignment parameters in order to allow a precise reconstruction of tracks and vertices. In addition to the initial optical survey and corrections for electronics and mechanical effects the use of tracks in a special software alignment is essential. A number of different methods is in use, ranging from simple residual-based procedures to complex fitting systems with many thousands of parameters. The methods are reviewed with respect to their mathematical basis and accuracy, and to aspects of the practical realization.

A new Silicon Photomultiplier structure for blue light detection

Abstract: Silicon Photomultipliers are extremely promising devices for those applications requiring the detection of very low-intensity light (down to single photon detection). The major drawback of the existing prototypes is the poor detection efficiency, especially at short wavelengths (below 10% in the blue region). In this paper, a new structure aimed at improving this parameter at wavelengths ranging from 400–450 nm is presented. With respect to a conventional structure it allows a maximization of the breakdown initiation probability for a given bias voltage and a reduction of the dead area. The analysis is supported by TCAD simulations.

Temperature dependences of LaBr3(Ce), LaCl3(Ce) and NaI(Tl) scintillators

Abstract: The temperature dependence of light output, energy resolution and decay time constants of the light pulses of NaI(Tl), LaCl3(Ce) (LaCl3) and LaBr3(Ce) (LaBr3) crystals were measured over the temperature range of −30 to 60 °C. In the study of the light output, the number of photoelectrons produced by the scintillators in the XP2020 photomultiplier was measured and corrected for by the temperature dependence of the quantum efficiency determined for 360 and 420 nm, respectively. It showed a high stability of the light output of LaBr3 of about 0.01%/°C and a comparable uniformity of LaCl3 at a long peaking time of 12 μs. The well-known thermal instability of NaI(Tl) was confirmed at a short peaking time of 2 μs. However, a much better stability of NaI(Tl) at low temperatures was observed for a long peaking time. The study of the decay of light pulses from LaCl3 and LaBr3 crystals confirmed earlier measurements, while NaI(Tl) showed a complex behavior at different temperatures. At low temperatures a strong contribution of a slow component of up to 60% of the total light was observed, while at elevated temperatures a well-known initial slow decay was replaced by a delayed maximum and the slow component became insignificant. The results of the study of energy resolution seem to be correlated with the variation of both the light output and a dependence of the decay time constants of the light pulses at changing temperature. This is particularly interesting in the case of NaI(Tl), where different dependencies of the energy resolution as a function of temperature for different peaking times in the spectroscopy amplifier were found. Tests of the XP2020 PMT itself showed that the thermal instability of the gain of the dynode structure of about−0.4%/°C is a dominating effect. The opposite effect on an increasing quantum efficiency, partly compensating for the gain instability, was observed above 10 °C for the longer wavelength of 420 nm.

The use of energy windowing to discriminate SNM from NORM in radiation portal monitors

Abstract: Energy windowing is an algorithmic alarm method that can be applied to plastic scintillator-based radiation portal monitor (RPM) systems to improve operational sensitivity to certain threat sources while reducing the alarm rates from naturally occurring radioactive material. Various implementations of energy windowing have been tested and documented by industry and at Pacific Northwest National Laboratory, and are available in commercial RPMs built by several manufacturers. Moreover, energy windowing is being used in many deployed RPMs to reduce nuisance alarms and improve operational sensitivity during the screening of cargo. This paper describes energy windowing algorithms and demonstrates how these algorithms succeed when applied to “controlled” experimental measurements and “real world” vehicle traffic data.

Signal variance in gamma-ray detectors-A review

Abstract: Signal variance in gamma-ray detector materials is reviewed with an emphasis on intrinsic variance. Phenomenological models of electron cascades are examined and the Fano factor ( F ) is discussed in detail. In semiconductors, F is much smaller than unity and charge carrier production is nearly proportional to energy. Based on a fit to a number of semiconductors and insulators, a new relationship between the average energy for electron–hole pair production and band gap energy is proposed. In scintillators, the resolution is governed mainly by photoelectron statistics and proportionality of light yield with respect to energy.

Marlin and LCCD—Software tools for the ILC

Abstract: The next big project proposed in particle physics is the International Linear Collider (ILC), an electron positron collider with an energy reach of around 1 TeV . The ongoing optimization and development of a detector for the ILC is only possible through the extensive use of sophisticated simulation software. In this paper we give a brief review of the software tools that are available in the currently ongoing three international detector concept studies and present two new software packages that have been developed in the context of the Large Detector Concept (LDC) study. The first is a C ++ application framework that provides a platform for the distributed development of reconstruction and analysis software and the second is a conditions data toolkit. The interoperability with other software packages is discussed.

Lanthanum halide scintillators: Properties and applications

Abstract: BrilLanCe®-350 and BrilLanCe®-380, Saint-Gobain Crystals’ trade-names for LaCl3:Ce and LaBr3:Ce are being brought to market under exclusive license to Delft and Bern Universities. We are reporting the properties of crystals produced with commercially viable processes and find they match others’ observations. These scintillators are bright (60,000 photons/MeV for LaBr3:Ce) and have very linear response, a combination that leads to very good energy resolution (

KM3NeT: Towards a km 3 Mediterranean neutrino telescope

Abstract: The observation of high-energy extraterrestrial neutrinos is one of the most promising future options to increase our knowledge on non-thermal processes in the universe. Neutrinos are e.g. unavoidably produced in environments where high-energy hadrons collide; in particular, this almost certainly must be true in the astrophysical accelerators of cosmic rays, which thus could be identified unambiguously by sky observations in “neutrino light”. To establish neutrino astronomy beyond the detection of single events, neutrino telescopes of km3 scale are needed. In order to obtain full sky coverage, a corresponding detector in the Mediterranean Sea is required to complement the IceCube experiment currently under construction at the South Pole. The groups pursuing the current neutrino telescope projects in the Mediterranean Sea, ANTARES, NEMO and NESTOR, have joined to prepare this future installation in a 3-year, EU-funded design study named KM3NeT (in the following, this name will also denote the future detector). This report will highlight some of the physics issues to be addressed with KM3NeT and will outline the path towards its realisation, with a focus on the upcoming design study.

Design and performance of the CMS pixel detector readout chip

Abstract: The readout chip for the CMS pixel detector has to deal with an enormous data rate. On-chip zero suppression is inevitable and hit data must be buffered locally during the latency of the first level trigger. Dead-time must be kept at a minimum. It is dominated by contributions coming from the readout. To keep it low an analog readout scheme has been adopted where pixel addresses are analog coded. We present the architecture of the final CMS pixel detector readout chip with special emphasis on the analog readout chain. Measurements of its performance are discussed.

Track reconstruction in the CMS tracker

Abstract: An overview of the track reconstruction algorithms used in the tracker of the CMS experiment at the LHC is presented. At the LHC, track reconstruction will be a very challenging task due to the high number of tracks foreseen. In addition to the standard Kalman filter, which serves as the basis for track reconstruction, several non-linear algorithms have been implemented.

Characterization of a ballistic supermirror neutron guide

Abstract: We describe the beam characteristics of the first ballistic supermirror neutron guide H113 that feeds the neutron user facility for particle physics PF1B of the Institute Laue-Langevin, Grenoble (ILL). At present, the neutron capture flux density of H113 at its 20×6 cm 2 exit window is Φ C = 1.35 × 1 0 10 cm - 2 s - 1 , and will soon be raised to above 2×10 10 cm −2 s −1 . Beam divergence is no larger than beam divergence from a conventional Ni-coated guide. A model is developed that permits rapid calculation of beam profiles and absolute event rates from such a beam. We propose a procedure that permits inter-comparability of the main features of beams emitted from ballistic or conventional neutron guides.

The LHCb DAQ interface board TELL1

Abstract: We have developed an electronic board (TELL1) to interface the DAQ system of the LHCb experiment at CERN. 289 TELL1 boards are needed to read out the different subdetectors. Each board can handle either 64 analog or 24 digital optical links. The TELL1 mother board provides common mode correction, zero suppression, data formatting, and a large network interface buffer. To satisfy the different requirements we have adopted a flexible FPGA design and made use of mezzanine cards. Mezzanines are used for data input from digital optical and analog copper links as well as for the Gigabit Ethernet interface to DAQ. The LHCb timing and trigger control signals are transported by a dedicated optical link, while the board slow-control is provided by an embedded PC running a Linux kernel.