One-dimensional Position Sensitive Detector Research Articles

Performance optimization of the scintillator neutron detectors for EMD in CSNS

Abstract Chinese Spallation Neutron Source (CSNS) has successfully produced its first neutron beam in 28th August 2017. It has been running steadily from March, 2018. According to the construction plan, the Engineering Materials diffractometer (EMD) will be installed between 2019- 2023. This instrument requires the neutron detectors with the cover area near 3m2 in two 90° neutron diffraction angle position, the neutron detect efficiency better than 40%@1Å, and the spatial resolution better than 4mm×200mm in horizontal and vertical directions respectively. We have developed an one-dimensional position sensitive neutron detector based on the oblique 6LiF/ZnS(Ag) scintillators, wavelength shifting fibers and SiPMs (Silicon Photomultipliers) readout. The inhomogeneity of the neutron detection efficiency between each pixel and each detector module, which caused by the inconsistency of the wave-length shifting fibers in collecting scintillation photons, need to be mitigated before the installation. A performance optimization experiment of the detector modules was carried out on the BL20 (Beam Line 20) of CSNS. Using water sample, the neutron beam with Φ5mm exit hole was dispersed relate evenly into the forward space. According to the neutron counts of each pixel of the detector module, the readout electronics threshold of each pixel is adjusted. Compared with the unadjusted detector module, the inhomogeneity of the detection efficiency for the adjusted one is improved from 69% to 90%. The test result of the diffraction peak of the standard sample Si showed that the adjusted detector module works well.

Improvement of simplified inclined plane test for evaluation of thickened liquids by using optical sensor.

The thickening management index for food for dysphagia is important in enabling recognition of the rheological properties of thickened liquids, including their static and dynamic properties. One of the static properties of these liquids is the yield stress. An improvement to the simplified inclined plane test is proposed here that involves use of an automatic system for measurement of the displacements of thickened liquids on an inclined plate. The aim of this study is to investigate the relationship between the displacements of the thickened liquids and the variable thickener concentrations using an optical sensor. To measure the displacement of each thickened liquid on a clear inclined plate, an optical sensor that has a 12-mm-long light receiving surface is selected to form a one-dimensional position-sensitive detector (1D-PSD) under the clear inclined plate. The relationship between the angle of inclination of the plate θ at which the maximum voltage occurred in the 1D-PSD and five thickener (xanthan gum) concentrations c, ranging from 1.0 to 3.0wt% in steps of 0.5wt%, was investigated. It was confirmed that an approximately linear plot was obtained under the condition that θ=8.24 c + 0.18, with the correlation R= .99 (for n= 7). This result indicated that the optical sensor composed of the 1D-PSD can measure the displacements of thickened liquids with various thickener concentrations on the clear inclined plate automatically.

High Resolution Residual Strain/Stress Measurements on Three Axis Neutron Diffractometer

Focusing 3-axis diffractometer set-up equipped with bent perfect crystal (BPC) monochromator and analyzer offers the sensitivity in determination of strains Dd/d < 10-4 in polycrystalline materials which is about one order of magnitude higher with respect to that of conventional 2-axis neutron scanners. It also offers possibility of line profile analysis for reasonable sample volumes and counting times. In this paper, the feasibility of using the 3-axis set-up even for measurements of rather large bulk polycrystalline samples with an acceptable resolution is presented. As the 3-axis set-up exploits focusing in real and momentum space, by a proper adjustment of the curvature of the analyzer, a high-resolution determination of the lattice changes can also be achieved even on large irradiated gauge volumes, though with a slightly relaxed resolution. It can be successfully exploited namely, in the strain/stress measurements on samples exposed to an external load, e.g. in tension/compression rig, in aging machine etc. In addition to the original performance where the analysis is carried out by rocking the BPC analyzer and the neutron signal registered by a point detector, a new alternative is offered which uses a fixed rocking angle position of the analyzer and the detector signal is registered by a one-dimensional position sensitive detector (PSD). This trick makes possible in some cases the elastic strain/stress measurements considerably faster and thus reduces the drawback of the time consuming step-by-step analysis.

One-dimensional parallax-free position-sensitive detector for diffraction measurements based on a home-made thin THGEM.

A large parallax-free gas diffraction meter based on a thinner-THGEM (thick gaseous electron multiplier) has been developed at the Beijing Synchrotron Radiation Facility (BSRF). A thinner-THGEM of thickness 200 µm is adopted, which can be shaped into a curve to eliminate parallax-error effects. The detector is designed to have a 48° open angle positioned 20 cm from the powder samples. A front-end electronics board with 128 channels direct-current mode was adapted for the 8 keV BSRF beamline with 0.2 ns/100 ns stable duty cycle. Two powder samples, TiO2 and SnO2, were tested separately. The measured spectra with an angular resolution of 0.148 ± 0.081° are consistent with the data from the powder diffraction file. Combining the gas gain of the thinner-THGEM with the electronic circuit dynamic range, a very broad dynamic range of about 107 could be obtained.

Vibration Measurement Method of a String in Transversal Motion by Using a PSD.

A position sensitive detector (PSD) is frequently used for the measurement of a one-dimensional position along a line or a two-dimensional position on a plane, but is more often used for measuring static or quasi-static positions. Along with its quick response when measuring short time-spans in the micro-second realm, a PSD is also capable of detecting the dynamic positions of moving objects. In this paper, theoretical modeling and experiments are conducted to explore the frequency characteristics of a vibrating string while moving transversely across a one-dimensional PSD. The theoretical predictions are supported by the experiments. When the string vibrates at its natural frequency while moving transversely, the PSD will detect two frequencies near this natural frequency; one frequency is higher than the natural frequency and the other is lower. Deviations in these two frequencies, which differ from the string’s natural frequency, increase while the speed of motion increases.

Basic design of a multi wire proportional counter using Garfield++ for ILSF

The Iranian Light Source Facility (ILSF) is a new 3 GeV third generation synchrotron radiation facility in Middle East, which at the time being is in its design stage. An important aspect for the scientific success of this new source will be the availability of well adapted detectors. Position-sensitive X-ray detectors have played an important role in synchrotron radiation X-ray experiments for many years and are still in use. An operational one-dimensional multiwire position sensitive detector with delay line readout produced by ILSF showed a position resolution of 230 μm. In this paper, we introduce a 2-D position sensitive gas detector based on a multiwire proportional chamber which will be used in small/wide angle scattering and diffraction experiments with synchrotron radiation at the ILSF. The parameters of its components, including the gas filling, gas pressure, temperature, the geometry of anode and cathodes planes as well as the expected performance of the designed system will be described in the following. For the design and the simulation of MWPC the Elmer and Garfield++ codes have been employed. We have built and tested a MWPC as a prototype at ILSF. The results obtained so far show a good position sensing. After primary test the detector has been optimized and is now ready for test at Elettra.

Simple and accurate optical height sensor for wafer inspection systems

An accurate method for measuring the wafer surface height is required for wafer inspection systems to adjust the focus of inspection optics quickly and precisely. A method for projecting a laser spot onto the wafer surface obliquely and for detecting its image displacement using a one-dimensional position-sensitive detector is known, and a variety of methods have been proposed for improving the accuracy by compensating the measurement error due to the surface patterns. We have developed a simple and accurate method in which an image of a reticle with eight slits is projected on the wafer surface and its reflected image is detected using an image sensor. The surface height is calculated by averaging the coordinates of the images of the slits in both the two directions in the captured image. Pattern-related measurement error was reduced by applying the coordinates averaging to the multiple-slit-projection method. Accuracy of better than 0.35 μm was achieved for a patterned wafer at the reference height and ±0.1 mm from the reference height in a simple configuration.

Novel method of detecting movement of the interference fringes using one-dimensional PSD.

In this paper, a method of using a one-dimensional position-sensitive detector (PSD) by replacing charge-coupled device (CCD) to measure the movement of the interference fringes is presented first, and its feasibility is demonstrated through an experimental setup based on the principle of centroid detection. Firstly, the centroid position of the interference fringes in a fiber Mach-Zehnder (M-Z) interferometer is solved in theory, showing it has a higher resolution and sensitivity. According to the physical characteristics and principles of PSD, a simulation of the interference fringe’s phase difference in fiber M-Z interferometers and PSD output is carried out. Comparing the simulation results with the relationship between phase differences and centroid positions in fiber M-Z interferometers, the conclusion that the output of interference fringes by PSD is still the centroid position is obtained. Based on massive measurements, the best resolution of the system is achieved with 5.15, 625 μm. Finally, the detection system is evaluated through setup error analysis and an ultra-narrow-band filter structure. The filter structure is configured with a one-dimensional photonic crystal containing positive and negative refraction material, which can eliminate background light in the PSD detection experiment. This detection system has a simple structure, good stability, high precision and easily performs remote measurements, which makes it potentially useful in material small deformation tests, refractivity measurements of optical media and optical wave front detection.

A Height Measurement Based on Laser Triangulation Probe and a Two Dimensional Image Measurement System for Smart Manufacturing

This paper integrated a laser triangulation probe with a two-dimensional image measurement system to measure the height of an object using the auto-focusing method. In the laser triangulation probe, the laser diode was used as the light source and one-dimensional position sensitive detector was adopted to receive the position of the laser spots to detect the height. The laser triangulation probe was used for small height measurement and the auto-focusing method was used for large height measurement. Two standard gauges with thicknesses of 8mm and 8.5mm were used to verify our proposed method. With height difference of 500μm, the experiment results showed the measuring error was within ±3μm and standard deviation was about 0.1μm.

Modified method for diffraction aberration of one-dimensional wire chamber

The one-dimensional position sensitive wire gaseous detector is developed for the synchrotron radiation diffraction, which consists of a single wire of gold-plated tungsten and 200 cathode strips as the readout. The induced signal is produced by the several adjacent cathode strips when X-ray is incident on anode wire with high voltage. Using the center gravity method to analyze the adjacent signals in one dimension, the primary ionization position of the X-ray can be obtained and the position resolution is 160 μm (FWHM). In Beijing Synchrotron Radiation Facility, the diffraction test is done at the experimental station. When the X-ray irradiates the crystal sample of SiO2, the different sizes of the diffraction rings can be produced. The diffraction angles are measured to be 11.148° and 14.201°, and the two-dimensional diffraction rings are reconstructed when the detector is moved and scanned with the several steps in the diffraction ring range. The diffraction aberration of one-dimensional wire chamber is very obvious. In the paper, the relevant influence factors of the detector construct are discussed. The thickness of the working gas and the width of active area window can give rise to the diffraction ring aberration. The theoretical calculation value of the diffraction aberration is larger than the position resolution value of the gaseous detector. The correction method is established based on the corresponding physical analysis, and by this method the value of the diffraction ring point is calculated. The relative aberration of diffraction position is improved by up to 7% with using the method, and the two-dimensional diffraction ring with no aberration can be reconstructed.

Evaluation of two thermal neutron detection units consisting of ZnS/6LiF scintillating layers with embedded WLS fibers read out with a SiPM

Two single channel detection units for thermal neutron detection are investigated in a neutron beam. They consist of two ZnS/6LiF scintillating layers sandwiching an array of WLS fibers. The pattern of these units can be repeated laterally and vertically in order to build up a one-dimensional position sensitive multi-channel detector with the needed sensitive surface and with the required neutron absorption probability. The originality of this work arises from the fact that the WLS fibers are read out with SiPMs instead of the traditionally used PMTs or MaPMTs. The signal processing system is based on a photon counting approach. For SiPMs with a dark count rate as high as 0.7MHz, a trigger efficiency of 80% is achieved together with a system background rate lower than 10−3Hz and a dead time of 30μs. No change of performance is observed for neutron count rates of up to 3.6kHz.

A position-sensitive tubular scintillator-based detector as an alternative to a 3He-gas-based detector for neutron-scattering instruments

A position-sensitive tubular scintillator-based neutron detector is proposed as an alternative to a 3He-gas-based detector. The detector has a neutron-detecting element constructed from rolled ZnS/6LiF scintillator screens that sandwich wavelength-shifting (WLS) fibre coils (SFC element). Multiple SFC elements are enclosed in an aluminium tube in a row to form a one-dimensional position-sensitive neutron detector. The design of the WLS fibre coil, which was determined by performing basic experiments, comprised two 0.75-mm-diameter WLS fibres wound in parallel at a pitch of 1.5mm. A 64-element detector with a pixel size of 22mm×20mm (width×length) successfully demonstrated the detection principle. The tubular shape of the new detector is similar to the usual 25-mm-diameter 3He tube, making this an alternative detector with the potential to be installed in a vacuum tank for inelastic-neutron-scattering instruments.

Attitude determination and control for centrifugal tether deployment on the ESTCube-1 nanosatellite

This paper presents the design, development, and pre-launch characterization of the ESTCube-1 Attitude Determination and Control System (ADCS). The design driver for the ADCS has been the mission requirement to spin up the satellite to 360 deg¢s i1 with controlled orientation of the spin axis and to acquire the angular velocity and the attitude during the scientific experiment. ESTCube-1 is a one-unit CubeSat launched on 7 May 2013, 2:06 UTC on board the Vega VV02 rocket. Its primary mission is to measure the Coulomb drag force exerted by a natural plasma stream on a charged tether and, therefore, to perform the basic proof of concept measurement and technology demonstration of electric solar wind sail technology. The attitude determination system uses three-axis magnetometers, three-axis gyroscopic sensors, and two-axis Sun sensors, a Sun sensor on each side of the satellite. While commercial off-the-shelf components are used for magnetometers and gyroscopic sensors, Sun sensors are custom- built based on analogue one-dimensional position sensitive detectors. The attitude of the satellite is estimated on board using an Unscented Kalman Filter. An ARM 32-bit processor is used for ADCS calculations. Three electromagnetic coils are used for attitude control. The system is characterized through tests and simulations. Results include mass and power budgets, estimated uncertainties as well as attitude determination and control performance. The system fulfils all mission requirements.

Energy dependence of highly charged ions guided through nanocapillaries in polycarbonate

The transmission of Xe10+ ions, with incident kinetic energies of 200–500 keV, through polycarbonate capillaries, with a diameter of 150 nm and a length of 30 μm, has been studied using a one-dimensional position sensitive detector. The transmitted ion yields were measured as a function of the tilt angle. The results are used to evaluate the guiding angle, which is a measure of the guiding power specifying the capability of insulating capillaries to guide ions at equilibrium. Following the semi-empirical scaling law, the potential in the entrance region in this work is nearly an order of magnitude larger than that proposed by low energy data.

Multiple position sensitive photodetector for optical differential detection

A Position Sensitive Detector (PSD) array formed by 64 one-dimensional PSDs is presented and characterized. Shallow and low-doped p–n junctions are formed by boron implantation in n-type silicon substrate to fabricate the PSD structure. The Lateral Photo-Voltage (LPV) of the device has shown a linear position characteristic within its whole length of about 2cm when irradiated by a He–Ne laser beam with a power of 1.74μW. The dependence of the LPV on the incident optical power was studied and saturation effects were observed for values above 10μW. Dual beam experiments were performed to study the concept of using single PSD as dual optical signal subtraction detector.

基于光子晶体的一维位置敏感探测器

基于光子晶体的一维位置敏感探测器

Theoretical study on enhancement of the lateral photovoltaic effect for position sensitive detector with resonant cavity

A one-dimensional (1D) position sensitive detector (PSD) with the active layer imbedded in resonant cavity is proposed. The lateral photovoltaic effect (LPE) on the surface of active layer is related to the lifetime of photo-generated carriers-electrons and holes pairs. Theoretically, by improving the transmittance of multiple layered systems, the lifetime of carriers can be lengthened. For a photodetector in near infrared, we design the multiple layered system stacked by alternating layers with MgF 2 and InP. The calculated result of electric field distribution in the proposed PSD is maximized in active layer with appropriate thickness. By this means, our aim is theoretically accomplished to enhance LPE in PSD based on resonant cavity structure.

Coaxial Adjusting Method for Irregular Rotating Workpiece

At present, most coaxial adjustment methods were evolved from traditional dial indicator coaxial adjustment method. The outer of the contour used as a benchmark to measure the axial and radial ruinous in these methods. However, these methods contain cylinder error of the shaft itself. To solve this problem, a method of using the double-layer one-dimensional Position Sensitive Detector (PSD) and laser was proposed. The laser should be fixed to the outside of the irregular rotating device, ensuring the two parts synchronous rotate ; the 6 one-dimensional PSD was divided to high and low 2 layers which were placed in coaxial position with the reference axis. The laser coaxial sweep passing the PSD, when laser coaxial and the irregular device rotate synchronous, the light of spot position on the PSD can determine the irregular rotating workpiece’s axes and the reference axis position relationship, the device can be used to adjust coaxial in this way.

Grazing-incidence in-plane X-ray diffraction on ultra-thin organic films using standard laboratory equipment

A novel grazing-incidence in-plane X-ray diffraction setup based on a commercial four-circle diffractometer with a sealed-ceramic copper X-ray tube, upgraded with parabolic graded multilayer X-ray optics and a one-dimensional position-sensitive detector, is presented. The high potential of this setup is demonstrated by a phase analysis study of pentacene thin films and the determination of in-plane lattice constants of pentacene mono- and multilayers. The quality of the results compare well to studies performed at synchrotron radiation facilities.

Establishment and Optimization of Angle Dispersive Neutron Diffraction Bulk Texture Measurement Environments

Different from electron back-scattering diffraction and X-ray diffraction, neutron diffraction enables to directly measure the bulk texture because of the high penetrability and the large spot size of neutron beam and easily investigate the preferred orientation distributions of multiphase materials, coarse-grained materials and low symmetric materials including hexagonal metals, ceramics and rocks. In this paper, the texture measurement technical environments of two angle dispersive neutron diffractometers were established and optimized respectively, and their reliabilities were quantitatively examined through evaluating the bulk textures of a warm-pressed magnesium alloy and a multilayered multiphase steel sheet. It is found that the MUSASI-L neutron diffractometer with a single tube detector through selecting the proper collimation angle may achieve the similar texture evaluation reliability to the RESA-2 neutron diffractometer with one-dimensional position-sensitive detector, so that both of them are available to directly measure the bulk textures of various materials. In addition, the estimation of thermal neutron absorption shows that if a measurement error about 5­8% is acceptable, a cubic sample or a cylinder samples whose diameters is equal to its height may be employed to directly measure its bulk texture through completely bathing it in the well-collimated uniform neutron beam without doing the correction of neutron absorption anisotropy. [doi:10.2320/matertrans.MA201203]