Dimensional Position Sensitive Detector Research Articles

A 3D CZT High Resolution Detector for X-and gamma-ray applications.

A high resolution three dimensional (3D) position sensitive CdZnTe-based detector was developed to detect high energy photons (10 keV-1MeV). The design of the 3D CZT detector, developed at DTU Space, is based on the CZT Drift Strip detector principle. The prototype detector contains 12 drift cells, each comprising one collecting anode strip with 3 drift strips, biased such that the electrons are focused and collected by the anode strips. The anode pitch is 1.6mm. The position determination perpendicular to the anodes, the X-direction, is performed using a novel interpolating technique. The position determination along the detector depth direction, Y-direction, is made using the depth sensing technique. The position determination along the anode strips, Z-direction is made with the help of 10 cathode strips orthogonal to the anode strips. REDLEN CZT crystals (20 mm x 20 mm x 5 mm) were used for the proto type detectors. IMEM-CNR fabricated the proto type detectors using a special surface treatment method and electrode attachment process. A novel method was applied to reduce the surface leakage current between the strips. The proto type detector was investigated at the European Synchrotron Radiation Facility, Grenoble which provided a fine 50 x 50 μm2 collimated X-ray beam covering an energy band up to 600 keV. At 400 keV we measured position resolutions of 0.2 mm FWHM in the X- and Y-direction and 0.6 mm FWHM in the Z-direction. The measured energy resolution of the detector was ~5.5 keV FWHM at 400 keV. The electronic noise contribution of the detector setup was 3.7 keV FWHM . The detector provides 3D position with very good spatial resolution as well as high resolution energy information and is therefore a well suited candidate e.g. as a Compton telescope detector, or for any application fields (medicine, security, science) where imaging and spectroscopy of high energy photons in the 10keV-1MeV range are required.

Thirty meters small angle neutron scattering instrument at China advanced research reactor

A high resolution 30m small angle neutron scattering (SANS) instrument has been constructed by the Institute of Chemistry, Chinese Academy of Sciences (ICCAS), and installed at China Advanced Research Reactor (CARR). It is equipped with a mechanical velocity selector, pinhole (including multi-pinhole) collimation system, sample chamber, and high resolution two dimensional 3He position sensitive neutron detector. The flexible variations of incident neutron wavelength, source to sample distance, sample to detector distance and the presence of neutron focusing lenses enable a wide Q range from 0.001Å−1 to 0.5Å−1 in reciprocal space and to optimize the resolution required. The instrument is the first SANS instrument in China, and can be widely used for the structure characterization of various materials, as well as kinetic and dynamic observation during external stimulation. The design and characteristics of the instrument are presented in the manuscript.

Principle of FT spectrometer based on a lateral effect position sensitive detector and multi channel Fabry–Perot interferometer

The principle of a new type of multi channel Fourier-Transform spectrometer based on a multi channel wedge Fabry–Perot interferometer using a one dimensional lateral effect Position Sensitive Detector and a scanning slit for interferogram readout have been shown. The design of this spectrometer is very compact and the readout electronics very simple. The drawback of using a scanning slit system is minimized by the use of a position sensitive detector where the position is inherently known for each measurement. Experiments show that the position can be resolved with high accuracy and the summation of the two photocurrents gives the interferogram distribution after scanning the slit between the wedge interferometer and the position sensitive detector. The spectral resolution obtained with a 25 mm wedge interferometer together with a 45 mm position sensitive detector and a 25 μm slit is about 5 nm around 600 nm wavelength range, which is close to the theoretically anticipated resolution. The evaluated spectrometer setup show promising results and could be used in applications where compact and low cost spectrometers are required.

Land mine detection with neutron back scattering imaging using a neutron generator

The neutron back scattering technique may be used to search for low-metallic land mines. An advantage of this technique is the speed of detection: the scanning speed may be made comparable to that of a metal detector. The method is sensitive to soil moisture. A limitation of the method is therefore that the soil must be sufficiently dry. The neutrons are produced with a pulsed neutron generator. An image of the back scattered thermal neutron radiation is obtained with a two dimensional position sensitive detector. Getting optimal settings for the detector system is described. The mine detection time as function of the neutron pulse parameters is investigated. Results with various dummy mines are presented

Development of a New High-resolution RBS System.

A compact high-resolution RBS system consisting of a 90o sector magnetic spectrometer (radius 200 mm), a quadrupole lens, an electrostatic deflector and a one dimensional position sensitive detector (length 100 mm) has been developed. The measured energy resolution of the spectrometer is 0.11% of the analyzing energy at an acceptance angle of 0.3 msr including the energy spread of the incident ion beam. Some observations using this new system are presented.

Modelling the operation of an a-Si:H based position sensitive detector

A physical model is presented which allows calculation of the carrier and potential distributions and the output voltage of a one dimensional position sensitive detector based on an ITO/a-Si:H/Pd structure. The calculation results are in agreement with those experimentally measured. Using the experimental data the effective electron diffusion length in the ITO layer is estimated to be about 0.65 cm. The effect of surface recombination on the device characteristics is studied by a numerical method.

Imaging Capabilities of the SODART Telescopes

The on- and off-axis imaging properties and effective area of the two SODARTflight telescopes have been measured using the expanded beam x-ray facility atthe Daresbury synchrotron. Following measurements have been done for bothFlight Model 1 & 2, at three energies: 6.627 keV, 8.837 keV and 11.046 keV.On-axis: Encircled Power Distribution, using one dimensional position sensitivedetector (1D-detector). Point Spread Function (PSF), using 1D-detector and two-dimensionalLEPC-type detector, FOV=33' (2D-detector). Effective Area, using 1D-detector.Off-axis: Point Spread Function, at off-axis angles 0.09°, 0.18° and 0.25°, using 2D-detector. Effective Area, estimates at off-axis angles in the interval [−0.4°,+0.4°], in steps of 0.05°, using 1D-detector.

X-ray absolute intensity measurement at HASYLAB ultrasmall angle x-ray scattering beamline BW4

In order to obtain small angle scattering intensities in absolute units, measurements of the incident beam intensity and the intensity transmitted through the sample are required. For this purpose the scattering intensity of a calibrated polyethylene (LUPOLEN) standard is used. For the determination of the absolute photon flux and the correction of the scattering patterns obtained with a two dimensional position sensitive detector we use the detector response function. A set of data measured subsequently at the standard and at a given sample can be evaluated in a program that calculates a pattern in absolute units corrected by means of the detector response. This program also calculates the absolute photon flux, determines automatically the center coordinates of the incident beam, and calculates the scattering vectors that belong to the different positions on the detector.

A two dimensional electron analyzer for electron-ion collisions

A toroidal electrostatic analyzer with a two dimensional position sensitive electron detector has been designed and built. The analyzer is installed to the electron spectrometer for measurements of the differential excitation cross sections in electron-ion collisions. The electron position is resolved in the energy and angular dispersive directions of the analyzer by means of microchannel plates and a charge dividing collector. The analyzer has an acceptance angle of 90°, and the analyzing energy range is 20% of the central pass energy with a relative energy resolution of 1%.

A position sensitive Gd detector for thermal neutrons

Abstract Si-strip detectors show qualities which are desirable in many neutron experiments, like excellent position— and time resolution and a low sensitivity to background radiation. To demonstrate the feasibility of this detector type for the detection of thermal neutrons, we tested a prototype of a one dimensional position sensitive neutron detector based on a Si-strip detector with a Gd-foil converter. A complete system consisting of the detector with VLSI electronics and an on-line data acquisition system has been constructed and tested. We present the first results of the measured position resolution and detector efficiency for neutrons with 1.1 A wavelength.

Visualisation of TOF-laue diffractometer data in reciprocal lattice space

SXD is a time-of-flight Laue diffractometer situated at ISIS. A suite of programs has been developed to convert SXD-data from raw data measured by the SXD two dimensional position sensitive detector into reciprocal lattice space and to visualise the

From Intelligent Materials to Smart Sensors: a-Si:H Position Sensitive Detectors

AbstractThis work presents the main static and dynamic performances showed by one dimensional thin film position sensitive detectors (ID TFPSD), based on a-Si:H technology, with a size of 80 mm × 5 mm. The results obtained show that the TFPSD is able to respond to light powers as low as 2μ W/cm2, presenting a detection accuracy, linearity and response frequency better than 10 gm, 2% and 2 KHz, respectively. These results are quite promising regarding the application of these sensors to a wide variety of optical inspection systems where continuous quality control is required.

A compact parallel plate detector for heavy ion reaction studies

A two dimensional position sensitive parallel plate detector, with an active area of 10 × 8 cm 2, was developed for heavy ion reaction studies. Position signals are extracted by using a non-standard compact delay-line, which allows saving dead spaces. The timing (≤280 ps) and position (1 mm in X, Y) resolutions of the detector make it a useful device for kinematic coincidence studies. Moreover, due to its mechanical construction, it is well suited for the implementation of a 4π structure to be built e.g. in the inner space of a Ge-array.

New array type electron multiplier as a two dimensional position sensitive detector

A new position sensitive array type electron multiplier using micromachining technique has been investigated. Here are described new miniature three dimensional structures for such a multichannel electron multiplier. Their preliminary processing and performance analyses are presented.

New ideas for two dimensional position sensitive silicon drift detectors

In this paper we present two new ideas for drift detectors with two dimensional position resolution. The first idea is based on the regular drift detector, but has a slightly different design in order to deal with diffusion problems. The second idea embodies a completely new type of drift detector that uses drift time measurements for both dimensions. The design consists of concentric quadrilateral closed strips with a small collecting anode in the centre. At first electrons travel perpendicular to the strips until they reach a diagonal. Then they proceed along this diagonal until they are collected at the centre. Position resolution in two dimensions can be obtained when both the time the electrons need to reach the diagonal and the time they need to reach the centre are measured. The latter is obtained from the collecting anode, the former from a diagonal strip present at the back side of the detector. Compared to common 2D drift detectors this detector offers the advantage of a small amount of read out electronics. It also has the advantage of having just one small collecting anode with a very low capacitance, resulting in low noise and therefore in a good energy resolution. >

Position detection of multiple light beams using phase detection

Earlier work on lateral-effect position-sensitive detectors (PSD) has used an amplitude detection signal-processing scheme to determine the position of the centroid of the incident light beam on the PSD surface. In this work we introduce a phase detection method of position measurement which is based on detecting the phase difference between the sinusoidal currents flowing through the metal electrodes. A distributed transmission line model for the PSD and a one-pole model for the transimpedance preamplifier are used in the analysis of the sensor. Experimental results are presented and are found to be in close agreement with simulation results. It is seen that the spatial resolution is proportional to the modulation frequency. With a light modulation frequency of 50 kHz and the introduction of frequency multiplication (/spl times/8) after the transimpedance preamplifier, a spatial resolution of 2 /spl mu/m is demonstrated. For application in multi-degree-of-freedom position sensors, we demonstrate the simultaneous detection of centroids of multiple light beams using frequency division multiplexing. Application of the phase method of position detection to a two dimensional PSD shows a maximum deviation from linearity of 1% over the working range of the PSD. >

Quantitative measurements on thermal neutron detectors based on storage phosphors

Two different two dimensional position sensitive detectors for thermal neutrons based on storage phosphors have been developed. The functional principles and quantitative measurements on the characteristic properties of both detector types are presented.

Accelerator Beam Experiments of a PrototypeCosmic Ray Heavy Ion Telescope

A Heavy Ion cosmic ray Telescope (HIT) has been scheduled to be launched into the synchronous orbit in 1993 aiming to observe elemental and isotopic composition of solar energetic particles and galactic cosmic rays. In this paper, we report the results of accelerator beam experiments of a prototype model of HIT. The telescope consists of two dimensional Position Sensitive Detectors (PSDs) and energy loss detectors (PIN type and Li-drifted type). The mass resolution was 1.1 amu in FWHM for 110 MeV/n pure iron ( 56 Fe) beam. By exposing HIT to beams consisting of various nuclides produced by the projectile fragmentation process in a reaction induced by 56 Fe beam, we confirmed that the secondary elements from 16 S to 25 Mn were clearly separated and that also the isotopes were separated for each elements lighter than 22 Ti. The observed mass resolution was 0.57 amu, 0.66 amu and 0.82 amu in FWHM for 18 Ar, 20 Ca and 22 Ti, respectively. We can conclude that the HIT has good prospects of enough ability for our current purpose in space observation.

New two dimensional position sensitive proportional detectors using charge division

Several two dimensional position sensitive proportional counters have been built. The cathodes can encode the position of the event in one or two dimensions using capacitative charge division techniques; a backgammon configuration encodes in one dimension with anode encoding of the second dimension, or a new cathode pattern can be used to encode in two dimensions. Details of the construction and performance are given.

Microstructure of high modulus solid state extruded polyethylene: 2. X-ray scattering studies of 12, 24 and 36 extrusion draw ratio

The microstructure of a series of solid state extruded polyethylene fibres was examined by wide- and small-angle X-ray scattering. By measuring absolute intensities using a two dimensional position sensitive detector, accurate values of the small-angle invariant for anisotropic samples were obtained. This measurement coupled with wide-angle X-ray scattering and d.s.c. permitted determination of the density of the noncrystalline component. The use of a two phase model for solid state extruded polyethylene is justified if consideration is given to the effective densities of the crystalline and noncrystalline phases, which change with deformation. The effective density of the crystalline phase decreases by 1% (0.999–0.990 g cm −3) from the unextruded billet compared to a 36 draw ratio extrudate, while the noncrystalline phase density increases by 6% (0.84–0.89 g cm −3). These changes lead to an overall decrease in the mean squared electron density fluctuation of 63%. The average axial crystallite length measured by wide-angle X-ray scattering increases with extrusion draw ratio while the SAXS long period decreases and weakens considerably. These observations and the electron microscopy results from the previous paper, ( Polymer, 1982, 23, 1069), are fully consistent with the key features of the Peterlin model of fibre microstructure.