Showing papers in "Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment in 2008"

Evaluation of theoretical conversion coefficients using BrIcc

Abstract: A new internal conversion coefficient database, BrIcc has been developed which integrates a number of tabulations on internal conversion electron (ICC) and electron–positron pair conversion coefficients (IPC), as well as Ω ( E 0 ) electronic factors. A critical review of general formulae and procedures to evaluate theoretical ICC and IPC values are presented, including the treatment of uncertainties in transition energy and mixing ratio in accordance with the Evaluated Nuclear Structure Data File. The default ICC table, based on the Dirac–Fock calculations using the so called “Frozen Orbital” approximation, takes into account the effect of atomic vacancies created in the conversion process. The table has been calculated for all atomic shells and to cover transition energies of 1–6000 keV and atomic numbers of Z = 5 –110. The software tools presented here are well suited for basic nuclear structure research and for a range of applications.

The DAMA/LIBRA apparatus

Abstract: The similar or equal to 250 kg highly radiopure NaI(Tl) DAMA/LIBRA apparatus, running at the Gran Sasso National Laboratory (LNGS) of the INFN, is described. (C) 2008 Elsevier B.V. All rights reserved.

The magnetized steel and scintillator calorimeters of the MINOS experiment

Abstract: The Main Injector Neutrino Oscillation Search (MINOS) experiment uses an accelerator-produced neutrino beam to perform precision measurements of the neutrino oscillation parameters in the “atmospheric neutrino” sector associated with muon neutrino disappearance. This long-baseline experiment measures neutrino interactions in Fermilab's NuMI neutrino beam with a near detector at Fermilab and again 735 km downstream with a far detector in the Soudan Underground Laboratory in northern Minnesota. The two detectors are magnetized steel-scintillator tracking calorimeters. They are designed to be as similar as possible in order to ensure that differences in detector response have minimal impact on the comparisons of event rates, energy spectra and topologies that are essential to MINOS measurements of oscillation parameters. The design, construction, calibration and performance of the far and near detectors are described in this paper.

Implementation of the Random Forest method for the Imaging Atmospheric Cherenkov Telescope MAGIC

Abstract: The paper describes an application of the tree classification method Random Forest (RF), as used in the analysis of data from the ground-based gamma telescope MAGIC. In such telescopes, cosmic gamma-rays are observed and have to be discriminated against a dominating background of hadronic cosmic-ray particles. We describe the application of RF for this gamma/hadron separation. The RF method often shows superior performance in comparison with traditional semi-empirical techniques. Critical issues of the method and its implementation are discussed. An application of the RF method for estimation of a continuous parameter from related variables, rather than discrete classes, is also discussed.

X-ray based methods for non-destructive testing and material characterization

Abstract: The increasing complexity and miniaturization in the field of new materials as well as in micro-production requires in the same way improvements and technical advances in the field of micro-NDT to provide better quality data and more detailed knowledge about the internal structures of micro-components. Therefore, non-destructive methods like radioscopy, ultrasound, optical or thermal imaging increasingly gain in importance with respect to ongoing product and material development in the different phases like material characterization, production control or module reliability testing. Because of the manifold different application fields, i.e., certain physical NDT methods applied to material inspection, characterization or reliability testing, this contribution will focus on the radioscopic-based methods related to their most important applications. Today, in modern industrial quality control, X-ray transmission is used in two different ways: • Two-dimensional radioscopic transmission imaging (projection technique), usually applied to inline inspection tasks in application fields like lightweight material production, electronic component soldering or food production. • Computed tomography (CT) for generation of three-dimensional data, representing spatial information and density distribution of objects. CT application fields are on the one hand the understanding of production process failure or component and module inspection (completeness) and on the other hand the dimensional measuring of hidden geometrical outlines (metrology). This paper demonstrates the methods including technical set-ups (X-ray source and detector), imaging and reconstruction results and the methods for high speed and high-resolution volume data generation and evaluation.

High resolution synchrotron-based radiography and tomography using hard X-rays at the BAMline (BESSY II)

Abstract: The use of high brilliance and partial coherent synchrotron light for radiography and computed tomography (CT) allows to image micro-structured, multi-component specimens with different contrast modes and resolutions up to submicrometer range This is of high interest for materials research, life science and non-destructive evaluation applications An imaging setup for microtomography and radiography installed at BESSY II (a third generation synchrotron light source located in Berlin, Germany) as part of its first hard X-ray beamline (BAMline) can now be used for absorption, refraction as well as phase contrast — dedicated to inhouse research and applications by external users Monochromatic synchrotron light between 6 keV and 80 keV is attained via a fully automated double multilayer monochromator For imaging applications the synchrotron beam transmitted by the sample is converted with a scintillator into visible light By use of microscope optics this luminescence image is then projected onto, eg, a CCD chip Several scintillating materials are used in order to optimise the performance of the detector system Different optical systems are available for imaging ranging from a larger field of view and moderate resolutions (macroscope — up to 14 mm × 14 mm field of view) to high resolution (microscope — down to 035 μ m pixel size), offering magnifications from 18 × to 40 × Additionally asymmetric cut Bragg crystals in front of the scintillator can be used for a further magnification in one dimension by a factor of about 20 Slow and fast cameras are available, with up to 16 bit dynamic range We show the suitability of the setup for numerous applications from materials research and life science

The Surface Detector System of the Pierre Auger Observatory

Abstract: The Pierre Auger Observatory is designed to study cosmic rays with energies greater than 10 19 eV. Two sites are envisaged for the observatory, one in each hemisphere,

The new μE4 beam at PSI: A hybrid-type large acceptance channel for the generation of a high intensity surface-muon beam

Abstract: At the Paul Scherrer Institute (PSI, Villigen, Switzerland) the existing μ E 4 decay muon channel has been replaced by a hybrid-type beam line consisting of two normal-conducting solenoids with rotational symmetry close to the muon production target E, followed by a conventional beam line composed of large aperture bending and quadrupole magnets with midplane symmetry. The new μ E 4 beam line with a design momentum of 28 MeV / c has been planned to deliver highest surface- μ + flux onto the 3 × 3 -cm 2 moderator target of the low-energy, polarized μ + source ( LE- μ + ) to generate an intense LE- μ + beam with tunable energy between 1 and 30 keV for muon spin rotation ( μ SR ) applications on thin films, multi-layers and near surface regions (depths ≲ 300 nm ). The main objective was the increase of solid-angle acceptance by about one order of magnitude taking into account stringent space limitations given by the geometry of the muon production target and the existing main shielding of the proton channel. Two normal-conducting solenoids as first focusing elements allow achieving this goal. With a solid-angle acceptance of Δ Ω ∼ 135 msr the new μ E 4 delivers currently the surface- μ + beam with highest flux of 4.2 × 10 8 μ + / s at a proton current of 2 mA, 4-cm long graphite production target E. About 40% of the beam can be focused onto the LE- μ + moderator target to generate LE- μ + with a rate up to 16 × 10 3 / s .

Systematic study of trace radioactive impurities in candidate construction materials for EXO-200

Abstract: The Enriched Xenon Observatory (EXO) will search for double beta decays of 136Xe. We report the results of a systematic study of trace concentrations of radioactive impurities in a wide range of raw materials and finished parts considered for use in the construction of EXO-200, the first stage of the EXO experimental program. Analysis techniques employed, and described here, include direct gamma counting, alpha counting, neutron activation analysis, and high-sensitivity mass spectrometry.

Evaluation of three methods for calculating statistical significance when incorporating a systematic uncertainty into a test of the background-only hypothesis for a Poisson process

Abstract: Hypothesis tests for the presence of new sources of Poisson counts amidst background processes are frequently performed in high energy physics (HEP), gamma ray astronomy (GRA), and other branches of science. While there are conceptual issues already when the mean rate of background is precisely known, the issues are even more difficult when the mean background rate has non-negligible uncertainty. After describing a variety of methods to be found in the HEP and GRA literature, we consider in detail three classes of algorithms and evaluate them over a wide range of parameter space, by the criterion of how close the ensemble-average Type I error rate (rejection of the background-only hypothesis when it is true) compares with the nominal significance level given by the algorithm. We recommend wider use of an algorithm firmly grounded in frequentist tests of the ratio of Poisson means, although for very low counts the overcoverage can be severe due to the effect of discreteness. We extend the studies of Cranmer, who found that a popular Bayesian-frequentist hybrid can undercover severely when taken to high Z-values. We also examine the profile likelihood method, which has long been used in GRA and HEP; it provides an excellent approximation in much of the parameter space, as previously studied by Rolke and collaborators.

First double-sided 3-D detectors fabricated at CNM-IMB

Abstract: The first results on double-sided three-dimensional (3-D) silicon radiation detectors are reported in this paper. The detector consists of a three-dimensional array of electrodes that penetrate into the detector bulk with the anode and cathode electrodes etched from opposite sides of the substrate. The geometry of the detector is such that a central anode is surrounded by four cathode contacts. The maximum drift and depletion distances are equal to the electrode spacing rather than detector thickness. This structure is similar to a conventional 3-D detector, but has a simpler fabrication process. The technological and the electrical simulations together with the fabrication steps of this new detector configuration are reported in this paper. The first detectors fabricated at CNM are reported here and have been characterized by electrical measurements.

The 1.5 GeV harmonic double-sided microtron at Mainz University

Abstract: At the Institut fur Kernphysik of Mainz University a harmonic double-sided microtron (HDSM) has been built to extend the experimental capabilities for nuclear and particle physics experiments to higher excitation energies. This novel microtron variant accelerates the 0.855 GeV continuous wave (cw) electron beam of the established three-staged race track microtron (RTM) cascade MAMI B up to 1.5 GeV. It consists of two normal conducting linear accelerators (linacs) through which the electrons are guided up to 43 times by a pair of 90°-bending magnets at each end. For beam dynamical reasons the linacs operate at the harmonic frequencies of 4.90 and 2.45 GHz. The extended facility is called MAMI C. The relatively strong vertical defocussing due to the 45°-pole face rotations (Fig. 1) at both the entrance and exit of the segment-shaped bending magnets is compensated for all recirculations by a suitable field decay in the magnets towards higher orbits. As a consequence, the energy gain of the electrons has to decrease with increasing turn number to maintain coherent acceleration. This occurs by an appropriate phase slip of the electron bunches downwards the rf-waves during the acceleration process. In this paper the functional principle and the beam dynamical concept of the double-sided microtron (DSM) as well as the design and development of its main components are described. Finally, the results of first beam measurements taken after starting up in December 2006 are discussed.

The 2.5-MeV neutron time-of-flight spectrometer TOFOR for experiments at JET

Abstract: A time-of-flight (TOF) spectrometer for measurement of the 2.5-MeV neutron emission from fusion plasmas has been developed and put into use at the JET tokamak. It has been optimized for operation a ...

Passive neutron detection for interdiction of nuclear material at borders

Abstract: Radiation portal monitor systems based upon polyvinyl toluene scintillator gamma-ray detectors and pressurized 3He-based neutron detector tubes have been deployed to detect illicit trafficking in radioactive materials at international border crossings. This paper reviews the neutron detection requirements and capabilities of passive, as opposed to active interrogation, detection systems used for screening of high-volume commerce for illicit sources of radiation at international border crossings. Computational results are given for the impact of cargo materials on neutron spectra, for the response of various detector geometries, the effects of backgrounds including “ship effect” neutrons, and for simulation of a large neutron detection array.

The AGILE Space Mission

Abstract: AGILE is an Italian Space Agency mission dedicated to the exploration of the gamma-ray Universe. The AGILE, very innovative instrument, combines for the first time a gamma-ray imager (sensitive in the range 30 MeV–50 GeV) and a hard X-ray imager (sensitive in the range 18–60 keV). An optimal angular resolution and very large fields of view are obtained by the use of state-of-the-art Silicon detectors integrated in a very compact instrument. AGILE was successfully launched on April 23, 2007 from the Indian base of Sriharikota and was inserted in an optimal low-particle background equatorial orbit. AGILE will provide crucial data for the study of Active Galactic Nuclei, Gamma-Ray Bursts, unidentified gamma-ray sources, galactic compact objects, supernova remnants, TeV sources, and fundamental physics by microsecond timing. The AGILE Cycle-1 pointing program started on 2007 December 1, and is open to the international community through a Guest Observer Program.

A detailed investigation of HPGe detector response for improved Monte Carlo efficiency calculations

Abstract: A detailed investigation of HPGe detector response for improved Monte Carlo efficiency calculations

Pixel detectors for imaging with heavy charged particles

Abstract: State-of-the-art single quantum counting pixel detectors offer a large potential for different imaging applications. The TimePix pixel device can provide information about position and energy of the detected radiation allowing radiography with charged particles. Heavy charged particles of known initial energy lose their energy partially by going through a specimen material. If the resulting energies of particles passing the specimen are measured, then specimen structure can be revealed. This article shows experimental results of this technique acquired with alpha particles and the TimePix detector. The spatial resolution in detector plane depends on particle energy and can reach submicrometer level. The specimen thickness can be determined with precision up to 320 nm for organic materials if energy loss of individual alpha particle is measured.

Advances in gaseous photomultipliers

Abstract: We review latest progress in gaseous photomultipliers (GPMs) combining solid photocathodes and various types of novel electron multipliers. Cascaded gaseous electron multipliers (GEMs) coated with CsI photocathodes can efficiently replace UV-sensitive wire chambers for single-photon recording in Cherenkov and other detectors. Other hole-multipliers with patterned electrodes (Micro-Hole and Strip Plates) and improved ion-blocking properties are discussed; these permit reducing considerably photon- and ion-induced secondary effects. Photon detectors with other electron-multiplier techniques are briefly described, among them GPMs are based on Micromegas, capillary plates, Thick-GEMs and resistive Thick-GEMs. The two latter techniques, robust and economically produced, are particularly suited for large-area GPM applications, e.g. in RICH. Cascaded hole-multipliers with very high ion-blocking performance permitted the development and the first demonstration of visible-sensitive GPMs operated in continuous mode, with bialkali photocathodes and single-photon sensitivity. Recent progress is described in GPMs operating at cryogenic temperatures for rare-event noble-liquid detectors and medical imaging.

TRIGA-SPEC: A setup for mass spectrometry and laser spectroscopy at the research reactor TRIGA Mainz

Abstract: The research reactor TRIGA Mainz is an ideal facility to provide neutron-rich nuclides with production rates sufficiently large for mass spectrometric and laser spectroscopic studies. Within the TRIGA-SPEC project, a Penning trap as well as a beamline for collinear laser spectroscopy are being installed. Several new developments will ensure high sensitivity of the trap setup enabling mass measurements even on a single ion. Besides neutron-rich fission products produced in the reactor, also heavy nuclides such as 235 U or 252 Cf can be investigated for the first time with an off-line ion source. The data provided by the mass measurements will be of interest for astrophysical calculations on the rapid neutron-capture process as well as for tests of mass models in the heavy-mass region. The laser spectroscopic measurements will yield model-independent information on nuclear ground-state properties such as nuclear moments and charge radii of neutron-rich nuclei of refractory elements far from stability. TRIGA-SPEC also serves as a test facility for mass and laser spectroscopic experiments at SHIPTRAP and the low-energy branch of the future GSI facility FAIR. This publication describes the experimental setup as well as its present status.

Development of CaMoO(4) crystal scintillators for double beta decay experiment with Mo-100

Abstract: We have studied the energy resolution, α / β ratio, temperature dependence of the scintillation properties, and the radioactive contamination of CaMoO4 crystal scintillators. We have also examined the use of pulse-shape discrimination to distinguish γ rays and α particles. A high sensitivity experiment to search for the 0 ν 2 β decay of Mo 100 using CaMoO4 scintillators is discussed.

Pattern recognition of tracks induced by individual quanta of ionizing radiation in Medipix2 silicon detector

Abstract: Medipix2 is a semiconductor pixel detector (256×256 pixels, 55×55 μm 2 each) which can count individual quanta of radiation. The detector will respond differently for different types of radiation. If the acquisition time is short enough with respect to radiation intensity, one can see characteristic tracks of individual quanta in an image taken (e.g., curved lines for electrons, round shaped clusters for alpha particles, heavy ions and slow neutrons, cone shapes for fast neutrons, simple dots for low energy X-rays, etc.). For effective visualization of neutrons, the device has to be equipped by corresponding neutron converter, which converts neutrons to heavy charged particles. By analyzing these patterns, in this so-called “tracking mode” of operation, it is possible to distinguish individual tracks and classify them into predefined categories. For each “cluster” detected, the features (such as parameters describing the shape and energy deposition estimation) can be extracted and used to distinguish radiation type. The energy deposited can be estimated by using calibration measurements with different types of radiation and variation of the discrimination threshold.

A new gadolinium-loaded liquid scintillator for reactor neutrino detection

Abstract: A high flash point, low toxicity gadolinium-loaded liquid scintillator (Gd-LS) has been developed for the detection of reactor neutrino. Carboxylic acid 3,5,5-trimethylhexanoic acid is used as complexing ligand to form organo-complex with gadolinium chloride, and 2,5-diphenvloxazole (PPO), and 1,4-bis[2-methylstyryl]benzene (bis-MSB) are used as primary fluor and wavelength shifter, respectively. The scintillator base is linear alkyl benzene (LAB). The Gd-LS prepared with such recipe has long attenuation length, high light yield and long-term stability. Eight hundred liters of Gd-LS (1 g/L Gd) was synthesized and tested in a prototype detector at Institute of High Energy Physics. Preliminary results of the obviously peaks corresponding to neutron captured by H and Gd give an additional evidence that such Gd-LS are very promising for anti-neutrino detection. (c) 2007 Elsevier B.V. All rights reserved.

Grain—A Java data analysis system for Total Data Readout

Abstract: Grain is a data analysis system developed to be used with the novel Total Data Readout data acquisition system In Total Data Readout all the electronics channels are read out asynchronously in singles mode and each data item is timestamped Event building and analysis has to be done entirely in the software post-processing the data stream A flexible and efficient event parser and the accompanying software system have been written entirely in Java The design and implementation of the software are discussed along with experiences gained in running real-life experiments

Reconstruction of longitudinal profiles of ultra-high energy cosmic ray showers from fluorescence and Cherenkov light measurements

Abstract: We present a new method for the reconstruction of the longitudinal profile of extensive air showers induced by ultra-high energy cosmic rays In contrast to the typically considered shower size profile, this method employs directly the ionization energy deposit of the shower particles in the atmosphere Due to universality of the energy spectra of electrons and positrons, both fluorescence and Cherenkov light can be used simultaneously as signal to infer the shower profile from the detected light The method is based on an analytic least-square solution for the estimation of the shower profile from the observed light signal Furthermore, the extrapolation of the observed part of the profile with a Gaisser–Hillas function is discussed and the total statistical uncertainty of shower parameters like total energy and shower maximum is calculated

CEM03.03 and LAQGSM03.03 Event Generators for the MCNP6, MCNPX, and MARS15 Transport Codes

Abstract: A description of the IntraNuclear Cascade (INC), preequilibrium, evaporation, fission, coalescence, and Fermi breakup models used by the latest versions of our CEM0303 and LAQGSM0303 event generators is presented, with a focus on our most recent developments of these models The recently developed “S” and “G” versions of our codes, that consider multifragmentation of nuclei formed after the preequilibrium stage of reactions when their excitation energy is above 2A MeV using the Statistical Multifragmentation Model (SMM) code by Botvina et al (“S” stands for SMM) and the fission-like binary-decay model GEMINI by Charity (“G” stands for GEMINI), respectively, are briefly described as well Examples of benchmarking our models against a large variety of experimental data on particle-particle, particle-nucleus, and nucleus-nucleus reactions are presented Open questions on reaction mechanisms and future necessary work are outlined

Performance of VAMOS for reactions near the Coulomb barrier

Abstract: VAMOS (VAriable MOde Spectrometer) is a large solid angle ray-tracing spectrometer employing numerical methods for reconstructing the particle trajectory. Complete identification of reaction products has been achieved by trajectory reconstruction. Equipped with a versatile detection system, VAMOS is capable of identifying reaction products from diverse reactions using beams at GANIL. The technique for trajectory reconstruction and its application for identifying reaction products are presented. The angular acceptance of the spectrometer has been studied using Monte Carlo simulation by an ion optics code. The spectrometer was coupled to the high efficiency EXOGAM γ-array to obtain γ-recoil coincidences for studying nuclei far from stability. The main features of the spectrometer as well as some results applied to experiments in deep inelastic collisions are described.

Unprecedented intensity of a low-energy positron beam

Abstract: A new in-pile γ -converter and Pt-moderator was recently installed at the neutron induced positron source NEPOMUC The intensity of the moderated positron beam is unprecedented and amounts to ( 90 ± 08 ) × 10 8 moderated positrons per second at an energy of 1 keV Hence, the beam facility NEPOMUC provides the world highest intensity of a monoenergetic positron beam reported so far Up to now, no degradation of the positron yield has been observed for several weeks of operation Thus, the long-term stability of the positron beam enables experiments with high reliability

The WASA detector facility at CELSIUS

Abstract: The WASA 4 pi multidetector system, aimed at investigating light meson production in light ion collisions and eta meson rare decays at the CELSIUS storage ring in Uppsala is presented. A unique fea ...

Digital pulse-shape discrimination of fast neutrons and γ rays

Abstract: Discrimination of the detection of fast neutrons and γ rays in a liquid scintillator detector has been investigated using digital pulse-processing techniques. An experimental setup with a 252Cf source, a BC-501 liquid scintillator detector, and a BaF2 detector was used to collect waveforms with a 100 Ms/s, 14 bit sampling ADC. Three identical ADCs were combined to increase the sampling frequency to 300 Ms/s. Four different digital pulse-shape analysis algorithms were developed and compared to each other and to data obtained with an analogue neutron– γ discrimination unit. Two of the digital algorithms were based on the charge comparison method, while the analogue unit and the other two digital algorithms were based on the zero-crossover method. Two different figure-of-merit parameters, which quantify the neutron– γ discrimination properties, were evaluated for all four digital algorithms and for the analogue data set. All of the digital algorithms gave similar or better figure-of-merit values than what was obtained with the analogue setup. A detailed study of the discrimination properties as a function of sampling frequency and bit resolution of the ADC was performed. It was shown that a sampling ADC with a bit resolution of 12 bits and a sampling frequency of 100 Ms/s is adequate for achieving an optimal neutron– γ discrimination for pulses having a dynamic range for deposited neutron energies of 0.3–12 MeV. An investigation of the influence of the sampling frequency on the time resolution was made. A FWHM of 1.7 ns was obtained at 100 Ms/s.