Use Of Position-sensitive Detector Research Articles

Lens-less PSD measurement of flexible link deflection

Accurate measurement of change in tip position and orientation of flexible links is of substantial importance for flexible robot control applications. In this paper, a measurement system is proposed to measure the change in position and orientation at the tip of a link subjected to bending and torsion with the use of position sensitive detector (PSD) sensors for space applications. Contrary to existing methods for measuring the spatial deflection of a flexible robot, the proposed method eliminates the requirement of a fragile lens or prism to obtain the angular displacement when PSD sensors are used. Experimental results for measuring five variables are presented for a cantilever flexible link when subjected to bending and torsion under a static load, thereby demonstrating the effectiveness of the proposed method.

Advances in position-sensitive photodetectors for PET applications

This paper presents a brief review of the use of position-sensitive detectors in positron emission tomography (PET) together with an overview of the near-future perspectives. Special attention is given to the development of a new class of magnetic field-compatible solid state photodetectors, the so-called silicon photomultipliers (SiPM).

Exploring the performance of [formula omitted]SR position-sensitive detectors through numerical simulations

Recently proposed improvements of the μ SR (muon spin rotation) technique include among others the use of position-sensitive detectors for the revelation of decay positrons. Unlike their high-energy particle counterparts, these detectors present specific peculiarities arising from the need of a relatively fast timing and from significant multiple scattering effects. By using advanced numerical simulation toolkits, such as Geant4, we explore the expected detector performance and possible ways for its optimisation. Intrinsic limits, finite pixel size effects, as well as the many parameters influencing the detector behaviour (distance, extension, angles, etc.) were thoroughly analysed and quantified, thus providing a valuable guide in prototype building and testing.

Position-sensitive detectors for muon spectroscopy: Design goals, constraints and perspectives

The new experimental challenges of modern μ SR require a critical review of the existing detection systems, whose limitations could be overcome by the use of position-sensitive detectors. The constraints posed by muon spectroscopy suggest silicon detectors and/or scintillating fibers as the most promising solutions. Realistic simulations using state-of-the-art Monte Carlo programs proved essential in detector optimization and in guiding prototype building.

Electron emission channeling with position-sensitive detectors

Electron emission channeling allows direct lattice location studies of low doses of radioactive atoms implanted in single crystals. For that purpose the anisotropic emission yield of conversion electrons from the crystal surface is measured, most conveniently by use of position-sensitive detectors. We discuss characteristic features of this method, including quantitative data analysis procedures, which are achieved by fitting simulated two-dimensional emission distributions for different lattice sites to the experimental patterns. The capabilities of this approach are illustrated by the case of rare earth atoms (Er, Tm, Yb) in Si, where we were able to do lattice location experiments down to implanted doses which are 150 times lower compared to previous RBS studies.

A neutron spin echo spectrometer with two optimal field shape coils for neutron spin precession

We have designed and have been constructing at the C 2−2 cold neutron guide port of JRR-3M, JAERI, a neutron spin echo spectrometer (NSE) which is equipped with two optimal field shape (OFS) coils for neutron spin precession with the maximum field integral of 0.22 T m, an assembly of position sensitive detectors (PSD), a converging polarizer and a wide area analyzer. The dynamic range of scattering vector Q covers from 0.005 Å −1 to 0.2 Å −1 and that of energy ħω from 10 neV to 30 μeV. Performance tests of the OFS coils show that the inhomogeneity of the magnetic field integral in the OFS coils with the spiral coils is so small that the NSE signal amplitude decreases little even for the neutron cross section of 30 ⊘mm diameter as the Fourier time t increases up to 25 ns, though the precession coils are close to iron covers of the neighboring neutron guide. This verifies that the OFS precession coils are appropriate for this NSE spectrometer. Another test experiment shows that the homogeneity condition of the precession magnet is loosened by use of PSD.

SIMION study of the fringing field effects in deflector-type electrostatic electron energy analyzers: A new flexible Jost-based correction scheme

The common use of physical stops (such as slits and apertures) at the entrance and exit planes of a deflector-type electrostatic electron energy analyzer often introduces unwanted distortions in the ‘‘ideal’’ equipotential distribution and reduces the deflection angle. Since Herzog’s classic work on the fringing field correction, a variety of correction schemes have been devised. Most of these correction methods are not entirely satisfactory particularly for applications that require the use of position sensitive detectors (PSDs). In the present work, we investigate the effects of physical stops and Jost plates on the fringing field in a standard hemispherical energy analyzer by using the electron ray-tracing simulation program SIMION. By balancing the fringing field effect due to the physical stops with that of the Jost plates, we extend the correction scheme proposed earlier by Jost. The present correction scheme has the advantages of ease of construction and compatibility with PSDs.

Ultrasmall-angle x-ray scattering at the HASYLAB wiggler beamline BW4

At the x-ray wiggler beamline BW4 a new instrument for small-angle x-ray scattering is available. It uses pinhole collimation thus allowing the use of position sensitive detectors for the data acquisition. It is equipped with a doubly focusing mirror and a double-crystal monochromator. The energy of the focused beam can be tuned in the range from 4 to 12 keV. Due to the high intensity of the wiggler source a geometry could be realized which extends the attainable range of scattering vector lengths markedly towards lower values compared with the previously existing instruments. Presently with the new instrument using 8 keV photons values down to 0.0016 nm−1 can be observed which corresponds to maximum correlation lengths of about 600 nm. This resolution is demonstrated, as an example, with measurements carried out on a polymer system.

The spring-8 project and the high pressure group in japan

Abstract Two major synchrotron radiation projects are presented, the conversion of the 30GeV TRISTAN collider into an ultra-high-brilliance machine and Spring-8, the 8 GeV Japanese third generation source. The Japanese high-pressure group is introduced and its plans for Spring-8 are described in the context of the proposed scientific programme which covers physics and chemistry, earth and planetary science, material science and shock wave compression. The equipment programme and requirements include multianvil presses with high-temperature capability, diamond-anvil cells with low- or high-temperature capabilities, shock compression apparatus and image-plate systems. The latest developments include a high-sensitivity ruby fluorescence detector and a fan-type multiple slit system to allow the use of position-sensitive detectors with multianvil devices. Presented at (he IUCr Workshop on ‘Synchrotron Radiation Instrumentation for HighPressure Crystallography’. Daresbury Laboratory 20-21 July 1991

Potential distribution and focusing properties of toroidal deflection plates: Application to simultaneous energy and angle-resolved charged particle spectroscopy

The potential distribution of toroidal deflection analysers is calculated in a new way which enables the determination of potential distributions to be made up to any desired order of accuracy. The calculations are valid for all kinds of toroidal analysers and can be applied to either “radial” particles that move at or about the (equatorial) plane of symmetry or “axial” particles that move at or about meridian planes that contain the axis of symmetry. The latter are of special interest because they enable the use of position-sensitive detectors. In both cases the particles are moving at or about circular main paths. For “axial” particles this can only be realized by adapting the shape of the deflection plates to non-circular cross-sections in meridian planes. Both potential calculations and numerical particle trajectory calculations are carried out to show that (for “axial” particles) better results are obtained for deflection plates adapted as above compared with the commonly used circular deflection plates. Calculations are carried out with reference to the EARISS analyser, which is the first analyser known to be equipped with such adapted deflection plates.

A class of condensing-collimating channel-cut monochromators for SAXS, XRPD, and other applications

We present design principles and examples for a new class of X-ray (and neutron) perfect-crystal monolithic monochromators which act to spatially condense and angularly collimate the resulting X-ray beam. Such condensing-collimating channel-cut (CCCC) monochromators can produce very narrow collimated beams and should prove very useful as beam concentrators for both synchrotron and conventional sources, and also in developing new types of high-resolution small-angle X-ray scattering (SAXS) and X-ray powder diffraction (XRPD) instruments, especially when these involve the use of position-sensitive detectors or imaging techniques.

The use of position-sensitive detectors in powder diffractrometry

The use of position-sensitive detectors in powder diffractrometry

Position-sensitive detector performance and relevance to time-resolved electron energy loss spectroscopy

The use of position-sensitive detectors (PSDs) has become common in many spectroscopies. The increased signal provided by the parallel detection of many spectral elements affords increases in sensitivity and/or time resolution. Recently, the use of a PSD to increase the temporal resolution of an electron energy loss (EEL) spectrometer has been demonstrated in our laboratory. This article summarizes the present development of EEL spectrometers and then presents a detailed review of four classes of PSDs in the context of their potential application to EEL spectroscopy (EELS). The four classes considered are (a) discrete channel detectors, (b) coincidence array detectors, (c) charge division detectors, and (d) optical detectors imaging phosphor screens. All four designs, as typically implemented, utilize microchannel plates (MCPs) as spatially imaging electron multipliers. The performance of MCPs is reviewed and the constraints that MCP behavior at the high count rates achievable in EELS places on acceptable PSD performance are outlined. The inability of present MCPs to maintain saturation gain at count rates above 1 MHz mm−2 implies that the PSD must tolerate significant gain reduction in the electron multiplier. The possibility of eliminating the MCP and using an electron-bombarded silicon gain mechanism is proposed. Such a device could, in principle, support count rates in excess of 100 MHz/channel, providing an order of magnitude increase in performance over the best existing detectors.

Characterization of semiconductor materials and devices by surface analysis techniques

In this review we consider some major surface analysis techniques: Rutherford backscattering (RBS); Auger electron spectroscopy (AES); X-ray photoelectron spectroscopy (XPS); ion scattering spectrometry (ISS) and secondary ion mass spectrometry (SIMS). Combined with ion bombardment for in-depth profiling some of these techniques provide three-dimensional composition distributions in a thin film. New instrumental developments are smaller electron and ion beam sizes and the increased use of position sensitive detectors. Spatial resolution and quantitative aspects are discussed; examples used are taken from semiconductor materials and device work.

Peak-shape analysis for protein neutron crystallography with position-sensitive detectors

In neutron protein crystallography, the use of position-sensitive detectors controlled by a modern data acquisition system permits new approaches to data collection strategies. Instead of dealing with conventional scans, like the θ-2θ scan, that provide an integrated intensity as a function of a rotational parameter, the computer-linked counter can be used to produce a three-dimensional reflection profile. As the crystal steps (Δω) through a reflection, the observed data for each step are stored in an external memory as a function of extent in 2θ and height (y) of a reflection. In this space, the reflection will be a three-dimensional distribution with dimensions determined by such basic geometrical conditions as Δλ, crystal size, mosaic spread, counter-resolution, and beam-collimation parameters. Knowledge of the interaction of these basic parameters will allow the design of optimal beam optics and will permit the delineation of the reflection from the background and permit, therefore, an accurate intensity determination.

New methods in molecular beam studies

A brief review is given of the development of methods used in investigations employing molecular beams. The topics discussed include the latest achievements in the development of gas-dynamic sources of molecular beams, the use of lasers in investigations employing beams, new methods of time-of-flight analysts of energies of particles in beams, and new possibilities associated with the use of position sensitive detectors based on secondary emission and utilizing microchannel plates.

Use of position sensitive detectors at energies below 1 MeV: Application to a fast determination of the pitch angle distribution of protons inside the magnetosphere

Experimental data which were obtained in the laboratory are presented, concerning the possible use of a position sensitive detector (P.S.D.) to determine the pitch angle and energy distribution of protons inside the magnetosphere. The pitch angle α is determined by putting a slit in front of the P.S.D. Each value of α is therefore associated with a value x of the abscissa of the particle impact on the P.S.D. A division of the two impulses (one being proportional to the particle energy E, and the other to the product of x by E) gives the value of x, hence of α. It is shown that the measurement of x is improved if one takes into account the correlated noise between the two impulses, E and xE. Experimental evidence is given that with such a system, one can achieve an angular resolution of 15° for E ≈ 0.1 MeV and 2.5° for E ≈ 1 MeV. Practical application to spin stabilized satellites is also considered.