Multi-element Detector Array Research Articles

Application of electronic time focusing at the engineering materials diffractometer in the China spallation neutron source

The Engineering Materials Diffractometer (EMD) is a new and critical addition to the instrument suite of the China Spallation Neutron Source (CSNS). It will support extensive research activities and applications on modern engineering materials. Based on the large multielement detector array, the electronic time focusing method has been successfully applied to deal with the raw neutron data and the constants Ci, corresponding to each single pixel in the detector array, have been calculated using the relation between the time of flight of the Bragg peaks in standard Si sample and their particular d-spacings. The instrument resolution in the mode best suited for strain measurements (∼0.35%) is interpreted and verified as a function of d-spacing via Si and La11B6 standard samples. The results are found to be consistent with the McStas simulations of the instrument physical design.

Formula omitted]-[formula omitted] fast timing at X-ray energies and investigation on various timing deviations

We report on systematic γ-γ fast-timing measurements by using four cylindrical 1.5′′×1.5′′ LaBr3(Ce) scintillator detectors which were installed in compact geometry around the focal plane of the Lohengrin fission-fragment separator at the Institut Laue–Langevin in Grenoble, France. Unconventional γ-ray sources as 185Os and 187W were produced by thermal-neutron activation to provide nearly prompt low-energy γ and K-X rays with average γ- and X-ray multiplicity equal to two. Due to practically no contribution of Compton background, highly precise results of time-walk measurements down to 40 keV are presented. Timing deviations related to different phenomena have been investigated, such as the geometry of an extended γ-ray source and the detector arrangement, long-term timing shifts and the timing contributions of the Compton background and the inter-detector Compton-scattering. The geometrical timing deviations are shown to be minimized using a multi-element detector array with a centrally symmetric arrangement relative to the center of the focal plane. Time-correction formula are proposed as analytical corrections for long-term time shifts, the time contributions of the Compton background and the position-dependent change of the time walk for cases where the calibration source cannot be placed at the center of the focal plane.

Photoelectric and optical properties of Schottky-barrier photodiodes based on IrSi–Si

The basic properties in the Schottky-barrier photodiodes (SBPDs) can be reduced to photon absorption in the silicide layer and internal photoemission of charge carriers from a metal to a semiconductor. Therefore, the quantum efficiency and photoresponse of these photodiodes (PDs) are primarily determined by electronic and optical processes in the metal silicide rather than in the semiconductor. This implies that, to a first approximation, the SBPD photoresponse is independent of semiconductor parameters such as the doping level, degree of compensation of impurities, and minority-carrier lifetime. The main reasons for photoresponse nonuniformity in multielement detector arrays are thereby ruled out.

Pulse-shape discrimination scintillators for homeland security applications

An extensive programme of research has been conducted for scintillation liquids and plastics capable of neutron–gamma discrimination for deployment in future passive and active Homeland Security systems to provide protection against radiological and nuclear threats. The more established detection materials such as EJ-301 and EJ-309 are compared with novel materials such as EJ-299-33 and p-terphenyl. This research also explores the benefits that can be gained from improvements in the analogue–to–digital sampling rate and sample bit resolution. Results are presented on the Pulse Shape Discrimination performance of various detector and data acquisition combinations and how optimum configurations from these studies have been developed into field-ready detector arrays. Early results from application-specific experimental configurations of multi-element detector arrays are presented.

Onset of quenching of the giant dipole resonance at high excitation energies

The evolution of the giant dipole resonance (GDR) properties in nuclei of mass $A=120$ to 132 has been investigated in an excitation energy range between 150 and 270 MeV through the study of complete and nearly complete fusion reactions using $^{116}\mathrm{Sn}$ beams at $17A$ and $23A$ MeV from the cyclotron of the Laboratorio Nazionale del Sud impinging on $^{12}\mathrm{C}$ and $^{24}\mathrm{Mg}$ targets. $\ensuremath{\gamma}$ rays and light charged particles were detected using the multi-element detector array MEDEA in coincidence with evaporation residues detected by using mass and charge identification spectrometry with telescope (MACISTE). Light-charged-particle energy spectra were analyzed within the framework of a multiple-source-emission scenario by using a fitting procedure to determine the amount of pre-equilibrium emission and deduce the excitation energies reached in the compound nuclei. A detailed analysis of the $\ensuremath{\gamma}$-ray spectra and their comparison with statistical model calculations is presented. Evidence of a quenching of the GDR gamma yield was found at 270 MeV excitation energy. The quenching effect becomes progressively more important with increasing excitation energy, as observed when the comparison is extended to data from the reaction $^{36}\mathrm{Ar}+^{96}\mathrm{Mo}$ at $37A$ MeV where hot nuclei were populated up to 430 MeV excitation energy. A coherent scenario emerges indicating the existence of a limiting excitation energy for the collective motion of about ${E}^{*}/A=2.1$ MeV for systems of mass $A=105$ to 111 while a slightly lower value was observed for nuclei of mass $A\ensuremath{\sim}132$. The existence of a possible link between GDR disappearance and the liquid-gas phase transition is discussed.

Optimizing the use of detector arrays for measuring intensity correlations of photon pairs

Intensity correlation measurements form the basis of many experiments based on spontaneous parametric down-conversion. In the most common situation, two single-photon avalanche diodes and coincidence electronics are used in the detection of the photon pairs, and the coincidence count distributions are measured by making use of some scanning procedure. Here we analyse the measurement of intensity correlations using multi-element detector arrays. By considering the detector parameters such as the detection and noise probabilities, we found that the mean number of detected photons that maximises the visibility of the two photon correlations is approximately equal to the mean number of noise events in the detector array. We provide expressions predicting the strength of the measured intensity correlations as a function of the detector parameters and on the mean number of detected photons. We experimentally test our predictions by measuring far-field intensity correlations of spontaneous parametric down-conversion with an electron multiplying CCD camera, finding excellent agreement with the theoretical analysis.

Focus on vacuum and cryogenics

Focus on vacuum and cryogenics

Third-generation infrared photodetector arrays

Hitherto, two distinct families of multielement detector arrays have been used for infrared (IR) imaging system applications: linear arrays for scanning systems (first generation) and two-dimensional arrays for staring systems (second generation). Nowadays, third-generation IR systems are being developed which, in the common understanding, provide enhanced capabilities such as larger numbers of pixels, higher frame rates, better thermal resolution, multicolor functionality, and/or other on-chip signal-processing functions. In this paper, fundamental and technological issues associated with the development and exploitation of third-generation IR photon detectors are discussed. In this class of detectors the two main competitors, HgCdTe photodiodes and quantum-well photoconductors, are considered. This is followed by discussions focused on the most recently developed focal plane arrays based on type-II strained-layer superlattices and quantum dot IR photodetectors. The main challenges facing multicolor devices are concerned with complicated device structures, thicker and multilayer material growth, and more difficult device fabrication, especially for large array sizes and/or small pixel dimensions. This paper also presents and discusses the ongoing detector technology challenges that are being addressed in order to develop third-generation infrared photodetector arrays.

SU-EE-A2-06: Using Multi-Element Detector Arrays for Commissioning Active Wobbling and Energy-Stacking Proton Beams

Multi-element detector arrays were constructed to characterize the properties of active wobbling and energy-stacking proton beam commissioning. A multi-layer ionization chamber (MLIC) array measured depth doses, and a multi-pad ionization chamber (MPIC) array measured lateral profiles. The MLIC consists of 122 chambers with 1.82mm spatial resolution and has an effective physical density about 60% that of water. The MPIC consists of 128 chambers arranged in two 38cm long orthogonal lines with spatial resolution of 5mm within 10cm radius and 7mm outwardly. During performance tests on the MLIC and MPIC, good collection efficiency with superior reproducibility and linearity were achieved. The relative variation on the sensitivity for each individual chamber was carefully calibrated before use for proton beam characterization. The relatively small charge collection area (6mm in diameter) and volume (0.3 cm3) of each chamber has a well guarded lead and allows one to study the effect of field size on depth dose distributions for fields of approximately 2 cm to 10 cm in diameter. The MLIC is calibrated using a pristine proton beam with range 27cm in water. To calibrate the large dimensional MPIC, uniform lateral dose distributions in water within 1% were generated. Analytical functions were applied to fit measured depth dose and lateral distributions in water during the calibrations. With proper calibrations, the uncertainties of measured depth doses and lateral profiles with these multi-element detector arrays were within 1% with respect to ones measured point by point with an ion chamber in a water phantom. Significant time savings for beam measurements were thus achieved.

A VMEbus based data acquisition system for a multi-element detector array

A data acquisition system based on VME standard modules has been designed for MULTICS, a multi-element detector array. The system is composed of a master crate housing CPU's, memories, interface and pattern boards. Up to 15 VME slave crates can be connected using the VMV vertical bus for ADC and TDC boards. A Macintosh Quadra is used as a console to provide a user friendly environment to send commands to the CPU's. Tools in the system include collecting and storing data, displaying histograms, handling all hardware parameters (high and low thresholds, rise time protection etc.). Diagnostic functions and error messages are also available to detect hardware failures or incorrect settings for the modules.

A multi-element detector array for heavy fragments emitted in intermediate energy nuclear reactions

To investigate complex fragment emission in intermediate energy nucleus-nucleus collisions, an array of three-element telescopes has been constructed. The array is designed to measure energy, charge and emission angles of fragments with Z values from 2 up to the projectile atomic number when studying reactions in reverse kinematics. In this case it has a good efficiency even for events with complex fragment high multiplicity. Each telescope is made of an ionization chamber (filled with CF 4 at a pressure up to 300 mbar), a Si detector (500 μm thick, position sensitive in two dimensions) and a CsI(Tl) scintillator with photodiode readout.

Plasma temperatures from first-hit neutron time-of-flight spectra

We describe a new technique for determining an inertial-confinement-fusion plasma temperature from a neutron time-of-flight spectrum recorded with a multielement detector array−even when each array element becomes fully saturated. A temperature uncertainty <20% is achieved over a yield range ≳10 000 using a 960-element array. Analysis of a spectrum formed by the first detected neutron (first hit) in each array element is used to determine the full spectrum’s temporal width. Temperatures for deuterium filled capsules have been determined from spectra recorded with the 20-m, 960-element LaNSA detector. A temperature of 0.88±0.09 keV was determined for a capsule producing only 1.4×106 neutrons. Temperatures determined for capsules yielding more than 2×109 neutrons are consistent with those determined with a 20-m current-mode time-of-flight detector.

A spatially resolved spectrally resolved photoluminescence mapping system

Whole wafer processing for the fabrication of opto-electronic devices provides significant advantages in terms of ease of handling and increased potential yield. However, it imposes a stringent demand on the development of non-destructive spatially resolved analytical methods to characterize substrates, epitaxial layers and devices. A photoluminescence system has been developed which allows rapid measurement of quantitative spectral information at a large number of spatial points. This allows the characterization of material quality and the development of systems for the deposition of higher quality and more highly uniform epitaxial layers. In this paper we will describe the SPM-200 photoluminescence system. This scanning stage system has the capability to quantitatively map wafers as large as 75 mm with a minimum sampling grid size of 2.5 μm. Photoluminescence signals from 450 to 2000 nm can be measured with the appropriate choice of detector and grating. Single element detectors and multi-element detector arrays can be used. The excitation can be software selected to be one of two premounted and prealigned lasers. The results of measurements on A1GaAs/GaAs and InGaAs(P)/InP epitaxial layers and GaAs substrates will be presented. Emphasis will be placed on the information that can be gained from not only spatial measurements at a single wavelength (topography) but also mapping of PL peak wavelength, intensity and full width half maximum. In addition to the room temperature measurements, low temperature (below 12 K) images of GaAs and other systems will be presented and discussed.

Nanosecond infrared absorption spectrometer

In the present publication, we describe the design details of a time-resolved IR absorption spectrometer with a broadband probe capability and nanosecond time resolution. The IR probe source is based on stimulated electronic Raman scattering in a metal vapor and has a measured pulsewidth of ~1 ns. Broadband collection of the IR light is facilitated by the unique use of a multielement detector array with its associated signal collection circuitry. The spectrometer has been used to record the IR spectra of some gas phase radicals which are indicative of its applicability to spectroscopic and kinetic investigations of short-lived molecular species.

オンラインにおけるカラー測定と管理

In paper manufacturing, there is a demand for on-line measurement of the color of paper sheet. This report describes the principles (spectrophotometers with a prism or grating and multi-element detector array are generally used to measure color), some different approaches, and relevant standards. The report also describes special considerations required for on-line measurement.

Thin film infrared detector arrays for integrated electronic structures

A new technique to obtain high quality middle i.r. detector arrays has been developed by the use of r.f. sputtering. Ternary chalcogenide layers with interesting properties for fabricating multielement detector arrays have been deposited by r.f. sputtering. Single crystal and polycrystalline Pb xSn 1−xTe and PbTe films have been investigated in the course of developing bidimensional detector arrays. Polycrystalline photoconductive detectors with exceptional responsivity and detectivity values have been obtained by means of reactive sputtering of PbTc and Pb xSn 1−xTe layers in an oxygen-tellurium-argon plasma atmosphere. This technique has allowed us to control the impedance and time constant values of the detectors in a very wide range just controlling the oxygen content in the gaseous sputtering plasma. Oxygen sensitizing effects in the photoconductive process are evidenced by Hall mobility, lifetime and spectral response vs temperature from room temperature down to liquid nitrogen. Photovoltaic properties of Pb xSn 1−xTe Ge heterojunctions are reported and discussed. These results are particularly important because silicon and germanium substrates can be used for incorporating the electronic readout elements, for both electronic switching and signal amplification, utilizing integrated cryogenic amplifiers and scanning circuits. Moreover high level performances can be achieved by integrating the high impedance policrystalline detectors into charge-coupled-device imaging systems.

Infrared detector arrays by new technologies

Techniques for fabricating single-crystal and thin-film detector arrays for infrared remote sensing have been developed in the last few years in most advanced solid-state laboratories. Arrays of photovoltaic devices have been prepared by liquid-phase epitaxy and vapor transport, and by the formation of metal-semiconductor structures and by proton bombardment. A great improvement in infrared thin-film devices was also achieved in the last few years by the vacuum deposition of epitaxial and polycrystalline films. A new technique to obtain high-quality middle-infrared detector arrays has been developed by the use of RF sputtering. Ternary chalcogenide layers with interesting properties for fabricating multi-element detector arrays have been obtained by an RF multicathode sputtering. Pb x Sn 1-x Te films, with a composition-dependent energy gap, have been deposited employing an RF multicathode sputtering system capable of simultaneous and sequential sputtering at different rates from three different targets. Single-crystal and polycrystalline films have been investigated in the course of developing bidimensional detector arrays. Heteroepitaxial films of Pb x Sn 1-x Te at substrate temperatures lower than that needed in conventional evaporation techniques have been obtained using NaCl and BaF 2 substrates. Moreover, epitaxial films with electrical properties close to the best single-crystal values have been obtained on germanium substrates. Using the cosputtering technique, it has been possible to obtain n-type and p-type layers just by controlling the quantity of excess metal or tellurium, respectively. Polycrystalline photoconductive detectors deposited by RF sputtering have shown responsivity and detectivity values higher than previously reported. Exceptionally high responsivity values have been obtained-better than 106V/W in PbTe films and 480 V/W in Pb 0.85 Sn 0.15 Te films. Peak detectivities D λ *(4.5 µ, 800, 1) > 8 × 1010cm ċ Hz1/2/W in PbTe detectors and D λ *(8.5 µ, 800, 1) > 109cm ċ Hz1/2/W in Pb x Sn 1-x Te detectors have been measured with a 2π-steradian field of view at an operating temperature of 77 K. These results are particularly important for the films deposited on germanium and silicon substrates, because of the easy incorporation of electronic readout elements into a completely integrated thermal vision system. Performance data are presented for blackbody and spectral detectivity, impedance, noise, and time constants. Distributions of measured data for linear staggered detector arrays are reported.

Detector array technology

The fabrication of multielement detector arrays represents the most advanced phase of the technology of any given detector material. The techniques which have previously proved satisfactory for the fabrication of single element state-of-the-art detectors are usually found to be inadequate for producing the multielement detector arrays required by current advanced i.r. systems. Detector requirements of these systems are high density patterns of very small elements with extreme dimensional accuracy plus a high degree of uniformity of the electrical and infrared characteristics of the individual elements. The technology of the fabrication of multielement detector arrays of the following materials is discussed briefly; InSb, Ge-Cu, Ge-Hg, PbSe and PbS. Performance characteristics of these arrays is given.