Two-dimensional Position Information Research Articles

Underwater optical guiding and communication solution for the AUV and seafloor node.

In this paper, an optical guiding and docking scheme is designed, and a node integrating laser positioning guidance and communication functions is developed. Through experiments, it is verified that the laser docking system has the function of guiding and communicating the autonomous underwater vehicle (AUV) with the support of the seabed observation network. It can provide two-dimensional position information for underwater platforms to navigate the media to sea network nodes and enable visual contact between them. The integrated terminals are small enough (6 cm in diameter) to be installed on small underwater platforms, such as AUVs. To safely work at a depth of thousands of meters, the devices have cylindrical shapes rather than spherical shapes. However, the cylindrical shell confines the view angle of the receiver. An optical system and a photodiode array are adopted to enlarge the cylindrical-shaped receiver's view angle. The positioning algorithm is designed based on the optical lens system and the photodiode array. In a small-pool experiment, this system is tested to achieve a data rate of 1 Mbit/s at a distance of 4 m. Positioning algorithms are also confirmed preliminarily in the small-pool experiment, and the error of the positioning algorithm is discussed.

An improved BP neural network‐based calibration method for the capacitive flexible three‐axis tactile sensor array

Flexible tactile sensing based on capacitive sensing has become a research hotspot in recent years because of its low energy consumption, high performance and wide application prospects. However, the axis error caused by the coupling deformation of the dielectric will seriously affect the accuracy of the sensor. In this paper, a capacitive flexible three-axis tactile sensor array is modelled and simulated, and a neural network-based calibrator for the three-axis sensor array is proposed, which can be used to calibrate the simulated measurement data. The simulation results show that even though the correlation coefficient of linear regression for each axis is very close to 1, the effect of dielectric nonlinear coupling distortion cannot be eliminated. The calibration method based on the neural network can effectively suppress the nonlinear coupling distortion of the dielectric, and reduce the measurement coupling rate of the sensor model from 26% to 1%. At the same time, in order to ensure the measurement accuracy and robustness of different units in the sensor array, the input layer of the calibrator is expanded, and the data set containing capacitance information and two-dimensional location information is used for training. The experimental results show that the proposed calibration method combining two-dimensional position information training accurately calibrates the capacitive flexible three-dimensional tactile sensor array.

Investigation of Model for Initial Phase of Communication

We propose an agent model that determines its behavior from an internal state and a spatial relationship with a target to generate approaching and avoiding behaviors in encounter scenes. This model is based on the relationship with an opponent rather than with a scenario. The agent moves to increase the utility value obtained from the preferences for both aggressive and passive involvement. We analyzed the behavioral and utterance data of human–human interactions based only on two-dimensional position information by simple-shaped robots. The rate of participants’ behavior following the model was significantly higher than that of a random walker. Based on this result, we estimated the internal state during the interactions from the behavior of the participants and analyzed it. The words uttered by one member of a pair correlated with the internal state estimated from the behavior of the other member of the pair. The frequency of the internal states observed from the participants who were recommended to interact with the partner was different from that observed from the participants who did not receive such recommendations. These results suggest that a model with two preferences can approximate a human’s internal state in encounter scenes.

TRD detector development for the CBM experiment

A transition radiation detector (TRD) prototype based on a single multiwire proportional chamber coupled with a small drift region was developed for the innermost part of the CBM-TRD subsystem. It preserves the same gas thickness for transition radiation absorption as the double-sided TRD prototype for which a pion misidentification probability of better than 1% for a six layer configuration was obtained. In the same time it fulfills the requirement of a high geometrical efficiency of CBM-TRD stations. The readout electrode geometry with triangular shaped pads gives access to a two-dimensional position information with a single TRD layer. The detector was tested with a mixed electron/pion beam of 1–5GeV/c momentum at the CERN PS accelerator. A pion misidentification probability of 1.18% for a six layer configuration based on this architecture was obtained. The two-dimensional position resolutions (along and across the pads) were measured. The pad signals were processed using a new front-end electronics called Fast Analog Signal Processor (FASP), designed for high-counting-rate environments. CADENCE simulations were used for further optimization of the FASP amplifier for operating this new architecture.

Fabrication and performance test of a silicon photo-strip detector coupled with a crystal scintillator

We developed a silicon photodetector optically coupled with a crystal scintillator. The silicon photodetector consists of a single crystal and two silicon photo-strip sensors. The silicon photo-strip sensor is designed and manufactured based on a concept of an AC-coupled single-sided silicon strip sensor, but the back-side of the strip sensor is modified to detect scintillation light. One scintillator is sandwiched between two photo-strip sensors. The p + strip arrays of the photo-strip sensors are oriented orthogonally to each other. This detector configuration provides the two-dimensional position information and the depth of interaction by measuring signal ratios between the first and the second photo-strip sensors. Theses sensors are fabricated on a 5 in., 380 μ m -thick , n-type and high resistivity silicon wafer. The leakage currents of the fabricated sensors are measured as a function of the reverse bias voltages. We also measured the photo response of the fabricated sensor for the wavelength range from 350 to 1000 nm. The energy resolution of the fabricated photodiode optically coupled with a CsI(Tl) crystal is obtained to be 13.8% for the 137Cs (662 keV) γ -rays . The one-dimensional position information by the α -particles from 241Am is obtained with the photo-strip sensor optically coupled with the CsI(Tl) crystal. We also measure the two-dimensional position of a LED light source with two photo-strip sensors.

A Performance and an Imaging Result of Silicon Strip Detector

Since capacitively coupled readout has an advantage of shielding the readout electronics from sensor leakage current, we fabricated an AC-coupled single-sided silicon strip sensor on 5-in. 380 μm-thick wafer and its active area is 3.2 × 3.2 cm2. It has 64 implanted and readout strips with a strip pitch of 500 μm. Two silicon strip sensors were mounted perpendicularly one another to get two-dimensional position information with a 5 mm space gap. Two low noise analog ASICs, VA1 chips, were used for signal readout of the strip sensor. The single-sided silicon strip detector (SSSD) consists of the two AC-coupled single-sided strip sensors and readout electronics. The SSSD was housed in an Al light-tight box. A CsI(Tl) scintillation crystal and a 2-in. photomultiplier tube were used to trigger signal events. The data acquisition systems were based on a 64 MHz FADC and control softwares for the PC-Linux platform. Experiments were performed at room temperature and silicon sensors were fully depleted. The SNRs were measured to be 29.1 ± 2.2 and 26.4 ± 0.3, respectively, for a 45 MeV proton beam and a 90Sr radioactive source. Imaging tests were performed using a Pb phantom with a 90Sr radioactive source and a 45 MeV proton beam, respectively. From the two-dimensional hit distribution, the phantom images were obtained and the position resolution was estimated to be about 240 μm.

A prototype of radiation imaging detector using silicon strip sensors

The aim of this work is to evaluate the performance of a strip sensor with a single photon counting data acquisition system based on VA1 readout chips to study the feasibility of a silicon microstrip detector for medical application. The sensor is an AC-coupled single-sided microstrip sensor and the active area of the sensor is 32.0 mm×32.0 mm with a thickness of 380 μm. The sensor has 64 readout strips with a pitch of 500 μm. The sensor was biased at 45 V and the experiment was performed at room temperature. Two silicon strip sensors were mounted perpendicularly one another to get two-dimensional position information with a 5 mm space gap. Two low noise analog ASICs, VA1 chips, were used for signal readout of the strip sensor. The assembly of sensors and readout electronics was housed in an Al light-tight box. A CsI(Tl) scintillation crystal and a 2-in. photomultiplier tube were used to trigger signal events. The data acquisition system was based on a 64 MHz FADC and control softwares for the PC-Linux platform. Imaging tests were performed by using a lead phantom with a 90Sr radioactive source and a 45 MeV proton beam at Korea Institute of Radiological and Medical Science in Seoul, respectively. Results of the S/ N ratio measurement and phantom images are presented.

Fabrication and Beta-Ray Source Test of Double-Sided Silicon Strip Sensor

Since a double-sided silicon strip sensor provides two-dimensional position information with high resolution, it has been developed for various uses as a medical imaging sensor, radiation detector, sensing detector in space science, and a silicon vertexing/tracking detector in experimental particle physics. We designed and fabricated a double-sided silicon position sensor in a 5 in. fabrication line. Silicon nitride with a silicon oxide layer was used to prevent damage during sensor fabrication. Since the temperature dependences of the silicon nitride and the silicon oxide are different, the thicknesses of the Si3N4 and SiO2 layers were optimized using the ATHENA process simulation to avoid cracks. We present the measurement results of the electrical characteristics of the sensor such as leakage current and capacitance as a function of reverse bias voltage. We performed tests on the sensor using a 90Sr radioactive source and measured the signal-to-noise ratio of the prototype sensor.

Silicon drift detectors, present and future prospects

Silicon drift detectors provide unambiguous two-dimensional position information for charged particle detection with a single detector layer. A large area silicon drift detector was developed for the inner tracking detector of the STAR experiment at RHIC. In this paper, we discuss the lessons learned and the future prospects of this technology.

Silicon drift detectors as tracking devices

Silicon drift detectors provide unambiguous two-dimensional position information for charged particle detection in a single detector layer. Like most other semi-conductor technologies, Silicon drift detectors are presently used in vertexing detectors. By taking into account, the drastic reduction in channel count compared to other silicon-based devices this specific technology is also well suited for large coverage tracking detectors. The first larger area Silicon Drift Tracker (6.3 cm×6.3 cm) was developed as the inner tracking detector (SVT) of the STAR experiment at the RHIC collider. Advantages and limitations of this detector will be discussed. Recent results of detector performance based on an application in a heavy ion fixed target experiment at the BNL-AGS (E896) are presented.

Design of a vacuum-compatible high-precision monochromatic beam-position monitor for use with synchrotron radiation from 5 to 25 keV

The Structural Biology Center beamline, 19ID, has been designed to take full advantage of the highly intense undulator radiation and very low source emittance available at the Advanced Photon Source. In order to keep the X-ray beam focused onto the pre-sample slits, a novel position-sensitive PIN diode array has been developed. The array consists of four PIN diodes positioned upstream of a 0.5 microm-thick metal foil placed in the X-ray beam. Using conventional difference-over-the-sum techniques, two-dimensional position information is obtained from the metal foil fluorescence. Because the full X-ray beam passes through the metal foil, the true beam center-of-mass is measured. The device is compact, inexpensive to construct, operates in a vacuum and has a working range of 8 mm x 10 mm that can be expanded with design modifications. Measured position sensitivity is 1-2 microm. Although optimized for use in the 5-25 keV energy range, the upper limit can be extended by changing metals or adjusting foil thickness.

X-ray powder diffraction with hybrid semiconductor pixel detectors

Semiconductor hybrid pixel detectors, originally developed for particle physics experiments, have been used for an X-ray diffraction experiment on a synchrotron radiation source. The spatial resolution of the intensity peaks in the diffraction patterns of silicon and potassium niobate powder samples was found to be better than that of a scintillator-based system, typically used at present. The two-dimensional position information of the pixel detector enabled multi-peak diffraction patterns to be acquired and clearly resolved without the need for an angle scan with a diffractometer. This trial experiment shows the potential of this technology for high-resolution high-rate diffraction systems.

A study of wire chambers with highly segmented cathode pad readout for high multiplicity charged particle detection

Investigations of interpolating cathode pad readout have been carried out for high-multiplicity, two-dimensional position-sensitive detection of minimum ionizing particles and heavy ions. A detector configuration representing only 0.6% of a radiation length and covering an area of 26 cm by 16 cm, with over 1000 readout channels, has been developed. In a prototype chamber using this technique, a resolution of less than 1090 mu m (RMS) for 5.4-keV X-rays and differential nonlinearity of +or-6% have been achieved. The technique has also been demonstrated for detectors of much larger area. Pad chamber and chevron pad types of detector have been built and used in the E814 heavy ion experiment at the Brookhaven National Laboratory Alternating Gradient Synchrotron. It is concluded that their ability to handle high particle multiplicity and provide unambiguous two-dimensional position information (1-3% readout node spacing along the wire direction) affords a very powerful detector technique. >

A detector system for discrete nuclide identification of ions with A ⩽ 60

An x− y position-sensitive detector system which provides simultaneous mass and charge identification with discrete nuclide resolution is described. This system is specially suitable for low-energy, medium-mass ( E 1 ≈ 1–10 MeV/mu; A ≈ 10–60) heavy tons. Charge identification is determined from a two-element gas-ionization counter coupled with a semiconductor stop detector. The gas-ionization counter employs a simple electron drift time technique to obtain two-dimensional position information. Mass identification is derived from measurement of the fragment time-of-flight with a pair of channel-plate time devices and the fragment energy, as provided by the ΔE y – ΔE x – E telescope. This system yields mass and charge resolution ⩽0.7 units in both A and Z and gives position resolutioon <0.5 mm for fragments with A ≲60, as determined from measurements performed with a 7.2 MeV/u 56Fe beam incident on 238U.