Showing papers in "Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment in 2004"

CompHEP 4.4 - Automatic Computations from Lagrangians to Events

Abstract: We present a new version of the CompHEP program (version 4.4). We describe shortly new issues implemented in this version, namely, simplification of quark flavor combinatorics for the evaluation of hadronic processes, Les Houches Accord-based CompHEP-PYTHIA interface, processing the color configurations of events, implementation of MSSM, symbolical and numerical batch modes, etc. We discuss how the CompHEP program is used for preparing event generators for various physical processes. We mention a few concrete physics examples for CompHEP-based generators prepared for the LHC and Tevatron.

Design, construction and tests of the ICARUS T600 detector

Abstract: We have constructed and operated the ICARUS T600 liquid argon (LAr) time projection chamber (TPC). The ICARUS T600 detector is the largest LAr TPC ever built, with a size of about 500 tons of fully imaging mass. The design and assembly of the detector relied on industrial support and represents the applications of concepts matured in laboratory tests to the kton scale. The ICARUS T600 was commissioned for a technical run that lasted about 3 months. During this period all the detector features were extensively tested with an exposure to cosmic-rays at surface with a resulting data collection of about 30 000 events. The detector was developed as the first element of a modular design. Thanks to the concept of modularity, it will be possible to realize a detector with several ktons active mass, to act as an observatory for astroparticle and neutrino physics at the Gran Sasso Underground Laboratory and a second-generation nucleon decay experiment. In this paper a description of the ICARUS T600 is given, detailing its design specifications, assembly procedures and acceptance tests. Commissioning procedures and results of the technical run are also reported, as well as results from the off-line event reconstruction.

Charged hadron tumour therapy monitoring by means of PET

Abstract: Positron emission tomography (PET) imaging of radioactivity distributions induced by therapeutic irradiation is at present the only feasible method for an in situ and non-invasive monitoring of radiooncology treatments with ion beams Therefore, at the experimental carbon ion therapy facility at the Gesellschaft fur Schwerionenforschung Darmstadt, Germany (GSI) a PET scanner has been integrated into the treatment site for quality assurance monitoring simultaneously to the therapeutic irradiation Although the device has been assembled from components of positron emission tomographs developed for nuclear medicine applications, substantial modifications had to be made for meeting the requirements of ion therapy monitoring These changes regard the geometrical detector configuration as well as the data acquisition and processing Since 1997 this technique has been applied to monitor the fractionated irradiation of more than 180 patients predominantly suffering from tumours in the head and neck region It could be demonstrated that this new PET technique is capable of assessing parameters being relevant for quality assurance of carbon ion therapy, ie the particle range in tissue, the position of the irradiated volume with respect to anatomical landmarks and local deviations between the planned and the applied dose distributions

CUORE: A cryogenic underground observatory for rare events

Abstract: CUORE is a proposed tightly packed array of 1000 TeO2 bolometers, each being a cube 5 cm on a side with a mass of 760 g . The array consists of 25 vertical towers, arranged in a square of 5 towers×5 towers, each containing 10 layers of four crystals. The design of the detector is optimized for ultralow-background searches: for neutrinoless double-beta decay of 130 Te (33.8% abundance), cold dark matter, solar axions, and rare nuclear decays. A preliminary experiment involving 20 crystals 3×3×6 cm 3 of 340 g has been completed, and a single CUORE tower is being constructed as a smaller-scale experiment called CUORICINO. The expected performance and sensitivity, based on Monte Carlo simulations and extrapolations of present results, are reported.

NINO: an ultra-fast and low-power front-end amplifier/discriminator ASIC designed for the multigap resistive plate chamber

Abstract: For the full exploitation of the excellent timing properties of the Multigap Resistive Plate Chamber (MRPC), front-end electronics with special characteristics are needed. These are (a) differential input, to profit from the differential signal from the MRPC (b) a fast amplifier with less than 1 ns peaking time and (c) input charge measurement by Time-Over-Threshold for slewing correction. An 8-channel amplifier and discriminator chip has been developed to match these requirements. This is the NINO ASIC, fabricated with 0.25 μ m CMOS technology. The power requirement at 40 mW/channel is low. Results on the performance of the MRPCs using the NINO ASIC are presented. Typical time resolution σ of the MRPC system is in the 50 ps range, with an efficiency of 99.9 % .

Detector description and performance for the first coincidence observations between LIGO and GEO

Abstract: For 17 days in August and September 2002, the LIGO and GEO interferometer gravitational wave detectors were operated in coincidence to produce their first data for scientific analysis. Although the detectors were still far from their design sensitivity levels, the data can be used to place better upper limits on the flux of gravitational waves incident on the earth than previous direct measurements. This paper describes the instruments and the data in some detail, as a companion to analysis papers based on the first data.

Thick GEM-like hole multipliers: properties and possible applications

Abstract: The properties of thick GEM-like (TGEM) gaseous electron multipliers, operated at 1–740 Torr are presented. They are made of a G-10 plate, perforated with millimeter-scale diameter holes. In single-multiplier elements, effective gains of about 10 4 , 10 6 , and 10 5 were reached at respective pressures of 1 and 10 Torr isobutane and 740 Torr Ar/5%CH 4 , with pulse rise-times in the few nanosecond range. The high effective gain at atmospheric pressure was measured with a TGEM coated with a CsI photocathode. The detector was operated in single and cascaded modes. Potential applications in ion and photon detection are discussed.

Novel type of avalanche photodetector with Geiger mode operation

Abstract: A novel type of avalanche photodetector with Geiger mode operation, known as Silicon Photomultiplier (SiPM) is presented. Development of photodetectors for the detection of low intensity photon flux is one of the critical issues for experimental physics, medical tomography and many others. The structure of the photodetector is based on metal–resistor semiconductor (MRS) microcells with a density of 1000/mm2, operating in the Geiger mode with an internal amplification gain of 105–106, with a photon detection efficiency of 32% for light in the green band of the visible spectrum, and a time resolution of about 30 ps. The structure of the photodetector gives the possibility of detecting a low flux of up to 1000 photoelectrons with proportional output. A Novel type of silicon photomultiplier is currently being tested for the TESLA scintillation tile hadron calorimeter.

Muon Track Reconstruction and Data Selection Techniques in AMANDA

Abstract: The Antarctic Muon And Neutrino Detector Array (AMANDA) is a high-energy neutrino telescope operating at the geographic South Pole. It is a lattice of photo-multiplier tubes buried deep in the polar ice between 1500 and 2000 m. The primary goal of this detector is to discover astrophysical sources of high-energy neutrinos. A high-energy muon neutrino coming through the earth from the Northern Hemisphere can be identified by the secondary muon moving upward through the detector. The muon tracks are reconstructed with a maximum likelihood method. It models the arrival times and amplitudes of Cherenkov photons registered by the photo-multipliers. This paper describes the different methods of reconstruction, which have been successfully implemented within AMANDA. Strategies for optimizing the reconstruction performance and rejecting background are presented. For a typical analysis procedure the direction of tracks are reconstructed with about 2° accuracy. © 2004 Elsevier B.V. All rights reserved.

Image Reconstruction and Material Z Discrimination via Cosmic Ray Muon Radiography.

Abstract: Highly penetrating cosmic ray muons shower the Earth at the rate of 10,000 m −2 min −1 at sea level. In our previous work (Nature 422 (2003) 277; Rev. Sci. Instr. 74(10) (2003) 4294; Cosmic Ray Muon Radiography for Contraband Detection, in: Proceedings of AccApp’03, San Diego, CA, June 2003), we presented a novel muon radiography technique which exploits the multiple Coulomb scattering of these particles for nondestructive inspection without the use of artificial radiation. In this paper, we describe the concept of and theory behind cosmic ray muon radiography. We discuss the information carried by the scattered muons and our approaches for exploiting that information with image reconstruction algorithms. We discuss preliminary and advanced reconstruction algorithms, which take advantage of the scattering angle, scattering location, and locations where strongly scattered muons cross paths. Our algorithms are validated with both experimental demonstrations and Monte Carlo simulations. Based upon the results from both the experiment and simulations, we conclude that scattering muon radiography can be useful for both material discrimination and fast (minute order) detection of compact high- Z objects. Our ray-crossing algorithm, which highlights locations where strongly scattered muons cross paths, is effective even in the presence of a medium- Z background matrix.

Basic instrumentation for Hall A at Jefferson Lab

Abstract: The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro-and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2 x 10(-4). A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10(38) CM-2 s(-1). The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium. (C) 2003 Elsevier B.V. All rights reserved.

Methods for multidimensional event classification: A case study using images from a Cherenkov gamma-ray telescope

Abstract: We present results from a case study comparing different multivariate classification methods. The input is a set of Monte Carlo data, generated and approximately triggered and pre-processed for an imaging gamma-ray Cherenkov telescope. Such data belong to two classes, originating either from incident gamma rays or caused by hadronic showers. There is only a weak discrimination between signal (gamma) and background (hadrons), making the data an excellent proving ground for classification techniques. The data and methods are described, and a comparison of the results is made. Several methods give results comparable in quality within small fluctuations, suggesting that they perform at or close to the Bayesian limit of achievable separation. Other methods give clearly inferior or inconclusive results. Some problems that this study can not address are also discussed.

Inorganic thermal-neutron scintillators

Abstract: A review is presented of research and development of inorganic scintillators for position-sensitive thermal-neutron detectors to be used at new spallation neutron sources.

The influence of energy weighting on X-ray imaging quality

Abstract: Recent developments in radiation imaging detectors offer a perspective towards energy sensitive X-ray pixel detectors. Such spectroscopic pixel detectors would provide energy information in addition to the spatial information. One way to use this additional energy information is to weight each photon by an energy dependent factor. Under stringent assumptions we can show how this energy weighting has to be performed to achieve maximum image quality. In order to visualise the impact of the weighting technique on the image quality we have simulated three radiologic cases with the EGS4-based Monte Carlo Roentgen Simulation ROSI (Nucl. Instr. and Meth. A 509 (2003) 151; www.pi4.physik.uni-erlangen.de/Giersch/ROSI).

Generating highly polarized nuclear spins in solution using dynamic nuclear polarization

Abstract: A method to generate strongly polarized nuclear spins in solution has been developed, using Dynamic Nuclear Polarization (DNP) at a temperature of 1.2 K, and at a field of 3.354 T, corresponding to an electron spin resonance frequency of 94 GHz. Trityl radicals are used to directly polarize C-13 and other low-gamma nuclei. Subsequent to the DNP process, the solid sample is dissolved rapidly with a warm solvent to create a solution of molecules with highly polarized nuclear spins. Two main applications are proposed: high-resolution liquid state NMR with enhanced sensitivity, and the use of the hyper-polarized solution as an MR imaging agent. (C) 2003 Elsevier B.V. All rights reserved.

CDF Central Outer Tracker

Abstract: The Central Outer Tracker is a large cylindrical drift chamber constructed to replace Collider Detector at Fermilab's original central drift chamber for the higher luminosity expected for Run 2 at the Fermilab Tevatron. The chamber's drift properties are described in the context of meeting the operating requirements for Run 2. The design and construction of the chamber, the front-end readout electronics, and the high-voltage system are described in detail. Wire aging considerations are also discussed.

Study of electron recombination in liquid argon with the ICARUS TPC

Abstract: Electron recombination in liquid argon (LAr) is studied by means of charged particle tracks collected in various ICARUS liquid argon TPC prototypes. The dependence of the recombination on the particle stopping power has been fitted with a Birks functional dependence. The simulation of the process of electron recombination in Monte Carlo calculations is discussed. A quantitative comparison with previously published data is carried out.

JYFLTRAP: a cylindrical Penning trap for isobaric beam purification at IGISOL

Abstract: A Penning trap has been installed for isobaric beam purification at the IGISOL-facility at the University of Jyvaskyla. In this paper, the technical details of this new device together with results of the first tests are presented. The mass resolving power, depending on the excitation parameters and the ion species, can be as high as 145 000 and the total transmission has been determined to be 17%. In addition, it is shown that with this experimental setup it is possible to measure atomic masses up to A=120 with accuracies of approximately 50 keV .

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

Abstract: 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.

Position-sensitive detector system OBI for High Resolution X-Ray Powder Diffraction using on-site readable image plates

Abstract: A one-dimensional detector system has been developed using image plates. The detector is working in transmission mode or Debye–Scherrer geometry and is on-site readable which reduces the effort for calibration. It covers a wide angular range up to 110° and shows narrow reflection half-widths depending on the capillary diameter. The acquisition time is in the range of minutes and the data quality allows for reliable Rietveld refinement of complicated structures, even in multi-phase samples. The detector opens a wide field of new applications in kinetics and temperature resolved measurements.

Data acquisition and analysis of the 76Ge double beta experiment in Gran Sasso 1990–2003

Abstract: Data acquisition in a long-running underground experiment has its specific experimental challenges, concerning data acquisition, stability of the experiment and background reduction. These problems are addressed here for the HEIDELBERG–MOSCOW experiment, which collected data in the period August 1990–May 2003. The measurement and the analysis of the data are presented. The duty cycle of the experiment was ∼80%, and the collected statistics is 71.7 kg year. The background achieved in the energy region of the Q value for double beta decay is 0.11 events / kg year keV . The two-neutrino accompanied half-life is determined on the basis of more than 100 000 events. The confidence level for the neutrinoless signal has been improved to a 4σ level.

Scintillation: mechanisms and new crystals

Abstract: The physical mechanisms active in inorganic scintillators used for medical imaging are reviewed briefly. These include relaxation of electronic excitation following initial absorption of high-energy radiation, thermalization of electrons and holes, formation of excitons, charge carrier trapping on defects and self-trapping, transfer of excitation to luminescence centers, and emission of detectable light. Materials include intrinsic and activated insulating crystals and semiconductors involving several different luminescent centers and radiative processes. Fundamental limitations of scintillator performance and nonradiative processes arising from native defects and impurities that can limit scintillation light output are discussed. The properties of several recently reported scintillating crystals are also presented.

Progress in FDC project

Abstract: FDC is a general-purpose program package for Feynman Diagram Calculation. We outline its achievements and focus on its recent progress, automatic construction of the Lagrangian and deduction of the Feynman rules for super-symmetry model, generation of multi-processes and their event generators in the SM and MSSM, and a few special applications. The FDC-homepage is presented to show the automatic translation of FDC's results into HTTP version. (C) 2004 Elsevier B.V. All rights reserved.

Electron cooling experiments at the ESR

Abstract: The properties of electron cooled beams of highly charged ions have been studied at the ESR. New experiments using a beam scraper to determine the transverse beam size provide the beam parameters in the intrabeam scattering dominated intensity regime, but also at very low intensity when the ion beam enters into an ultra-cold state. Extremely low values of longitudinal and transverse beam temperature on the order of meV were achieved for less than 1000 stored ions. An experiment with bunched ultra-cold beam showed a limit of the line density which agrees with the one observed for coasting beams. Cooling of decelerated ions at a minimum energy of 3 MeV /u has been demonstrated recently.

Monte Carlo simulation in PET and SPECT instrumentation using GATE

Abstract: Monte Carlo simulation is an essential tool to assist in the design of new medical imaging devices for emission tomography. On one hand, dedicated Monte Carlo codes have been developed for PET and SPECT. However, they suffer from a variety of drawbacks and limitations in terms of validation, accuracy, and/or support. On the other hand, accurate and versatile simulation codes such as Geant3, EGS4, MCNP, and recently Geant4 have been written for high energy physics. They all include well-validated physics models, geometry modeling tools and efficient visualization utilities. Nevertheless these packages are quite complex and necessitate a steep learning curve. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries in order to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the users to describe time-dependent phenomena such as detector movements or source decay kinetics, thus allowing to simulate time curves under realistic acquisition conditions. At present, it is being further developed and validated within the OpenGATE Collaboration. We give a succinct overview of GATE and four examples of its validation against real data obtained with PET and SPECT cameras.

New experimental validation of the pulse height weighting technique for capture cross-section measurements

Abstract: The accuracy of the pulse height weighting technique for the determination of neutron capture cross-sections is investigated. The technique is applied to measurements performed with C6D6 liquid scintillation detectors of two different types using capture samples of various dimensions. The data for well-known (n, gamma) resonances are analyzed using weighting functions obtained from Monte Carlo simulations of the experimental set-up. Several causes of systematic deviation are identified and their effect is quantified. In all the cases measured the reaction yield agrees with the standard value within 2%.

Data handling, reconstruction, and simulation for the KLOE experiment

Abstract: The broad physics program of the KLOE experiment is based on the high event rate at the Frascati φ factory, and calls for an up-to-date system for data acquisition and processing. In this review of the KLOE offline environment, the architecture of the data-processing system and the programs developed for data reconstruction and Monte Carlo simulation are described, as well as the various procedures used for data handling and transfer between the different components of the system.

Advanced geometries for ballistic neutron guides

Abstract: Sophisticated neutron guide systems take advantage of supermirrors being used to increase the neutron flux. However, the finite reflectivity of supermirrors becomes a major loss mechanism when many reflections occur, e.g. in long neutron guides and for long wavelengths. In order to reduce the number of reflections, ballistic neutron guides have been proposed. Usually linear tapered sections are used to enlarge the cross-section and finally, focus the beam to the sample. The disadvantages of linear tapering are (i) an inhomogeneous phase space at the sample position and (ii) a decreasing flux with increasing distance from the exit of the guide. We investigate the properties of parabolic and elliptic tapering for ballistic neutron guides, using the Monte Carlo program McStas with a new guide component dedicated for such geometries. We show that the maximum flux can indeed be shifted away from the exit of the guide. In addition we explore the possibilities of parabolic and elliptic geometries to create point like sources for dedicated experimental demands.

MCP-PMT timing property for single photons

Abstract: We have measured the performance, especially the timing properties, of micro-channel plate photo-multiplier tubes (MCP-PMTs) by irradiating with single photons with/without a magnetic field. A time resolution of σ=30– 35 ps was obtained for single photons under 1.5 T . With an MCP-PMT, a small time-of-flight counter, by means of Cherenkov light radiation instead of scintillation light has been prepared, and a time resolution σ∼10 ps was attained for a high-energy π-beam by multiple photons.

Performance of triple GEM tracking detectors in the COMPASS experiment

Abstract: COMPASS is a high-luminosity fixed target experiment at CERN's SPS, which has been taking data with a 160 GeV / c muon beam since 2001. The tracking of charged particles in the near-beam area is achieved by a set of twenty novel large-area micropattern gas detectors based on the Gas Electron Multiplier (GEM). Owing to a two-dimensional readout of signals, each of these detectors delivers two track projections. Distributed over a distance of 30 m throughout the spectrometer, the GEM detectors constitute the backbone of the small-area tracking system of COMPASS. The performance of these detectors in the high intensity muon beam with particle rates up to 25 kHz / mm 2 is investigated.