Automated Scanning System Research Articles

A Method for Determining X‐ray Elastic Constants for the Measurement of Residual Stress

Abstract: The X‐ray diffraction method is arguably the most convenient method of measuring residual stresses in terms of cost, spatial resolution, measurement time and the accuracy of measurement. The normal methods for calibrating X‐ray diffractometers are not conveniently applied to automated scanning systems, however, and so a new approach is required. In this study, a scanning X‐ray diffractometer was calibrated and the X‐ray elastic constant for a steel alloy was determined using a customised four‐point bending rig. The bending rig, in turn, was calibrated by dead loading. This study also described a simple alternative method for determining the X‐ray elastic constant, without the use of specialised software. After calibration, the error band of the diffractometer was found to be less than ±10 MPa. As this is ±5% of the yield stress for a typical steel, this level of accuracy was deemed to be acceptable for the measurement of residual stress.

Measurement of Λc+ production in neutrino charged-current interactions

A measurement of Λc+ production in neutrino nucleon charged-current interactions is presented. In a subsample of about 50000 interactions located in the emulsion target of the CHORUS detector, exposed to the wide band neutrino beam of the CERN SPS, candidates for decays of short-lived particles were identified using new automatic scanning systems and later confirmed through visual inspection. Criteria based on the flight length allowed a statistical separation among the different charm species thus enabling a sample particularly rich in Λc+ to be defined. At an average neutrino energy of 27 GeV, the product σ(Λc+)/σ(CC)×BR(Λc+→3p) was measured to be (0.37±0.10(stat)±0.02(syst))×10−2, while the values of (1.54±0.35(stat)±0.18(syst))×10−2 and of 0.24±0.07(stat)±0.04(syst) were obtained for σ(Λc+)/σ(CC) and BR(Λc+→3p), respectively.

Determination of the semi-leptonic branching fraction of charm hadrons produced in neutrino charged-current interactions

During the years 1994–1997, the emulsion target of the CHORUS detector was exposed to the CERN-SPS Wide Band Neutrino Beam. The improvements of the past few years in the automatic emulsion scanning systems allowed a sample of events located in emulsion to be used for studies of charm production. Based on a sample of 56172νμ charged-current interactions analysed so far, we find a value of Bμ=0.093±0.009(stat.)±0.009(syst.) for the semi-leptonic branching fraction of charm hadrons. The result for events with visible energy larger than 30 GeV, Bμ=0.102±0.016(stat.)±0.010(syst.), can be combined with the existing measurements of the dimuon rate to yield a value of 0.219±0.022 for the magnitude of the Cabibbo–Kobayashi–Maskawa matrix element |Vcd|.

Automatic scanning system for the determination of local loss distributions in magnetic cores

The paper describes an automatic scanning system for the determination of local loss distributions in magnetic cores based on the rise-of-temperature method. The drawback of long measurement times is accepted opposite to the performance of unsupervised overnight operation. The reported measurements on model transformer cores indicate a good accuracy close to 5%.

Deuterium plasma focus measurements using solid state nuclear track detectors

A camera obscura technique was used to investigate the spatial distribution of fusion protons emitted from a small deuterium plasma focus device operated in its neutron-optimized regime (14 kV, 3 kJ, and 400 Pa D2 gas). An indium-foil activation detector was employed simultaneously to measure the shot-to-shot neutron yield. The camera obscura was positioned on the forward axis of the plasma focus, 12 cm from the tip of the hollow copper anode, covering a conical field-of-view of half-angle slightly less than 20 degrees. The nuclear track detector material PM-355 was used in the camera focal plane to register protons from the 2H(d, p)3H reaction, hence imaging the spatial distribution of fusion occurring in the plasma focus. A kapton film covering the camera entrance pupil served to protect the detector from the hot plasma jet; it also stopped completely all energetic charged particles other than the ( 3 MeV) fusion protons. Following chemical etching of the detector plates, the track parameters - size, circularity, average-grey-value and (x-y) position - |were measured by an automated scanning system comprising an optical microscope equiped with a CCD camera, motorized stage and focus-adjust, and interfaced to a PC computer. From the accumulated track data, representing 119 plasma focus shots, the imaged fusion density profile was obtained. A detailed Monte Carlo simulation program was used to interpret this profile. The results indicate that the beam-target mechanism, in which energetic deuterons emitted in a forwardly directed cone from the plasma focus pinch interact with the cold deuterium gas, accounts for 90 to 96% of the fusion production for our device. There is however clear evidence for a non-zero (4 to 10%) contribution emitted directly from the pinch region.

Measurement of D0 production in neutrino charged-current interactions

Abstract During the years 1994–1997, the emulsion target of the CHORUS detector was exposed to the Wide Band Neutrino Beam from the CERN-SPS. About 170 000 neutrino interactions were successfully located in the emulsion. Improvements in the automatic emulsion scanning systems and application of different criteria allowed the sample of located events to be used for studies of charm production. We present a measurement of the production rate of D 0 mesons based on a sample of 25 693 located ν μ charged-current (CC) interactions analysed so far. After reconstruction of the event topology in the vertex region, 283 D 0 decays were observed with an estimated background of 9.2 K 0 and Λ decays. The ratio of cross-section of D 0 production and ν μ CC interactions is found to be (1.99±0.13(stat.)±0.17(syst.))×10 −2 at 27 GeV average ν μ energy.

Automatic scanning for nuclear emulsion

Automatic scanning systems have been recently developed for application in neutrino experiments exploiting nuclear emulsion detectors of particle tracks. These systems speed up substantially the analysis of events in emulsion, allowing the realisation of experiments with unprecedented statistics. The pioneering work on automatic scanning has been done by the University of Nagoya (Japan). The so called new track selector has a very good reproducibility in position ( ∼1 μ m) and angle (∼3 mrad), with the possibility to reconstruct, in about 3 s, all the tracks in a view of 150×150 μm 2 and 1 mm of thickness. A new system (ultratrack selector), with speed higher by one order of magnitude, has started to be in operation. R&D programs are going on in Nagoya and in other laboratories for new systems. The scanning speed in nuclear emulsion be further increased by an order of magnitude. The recent progress in the technology of digital signal processing and of image acquisition systems (CCDs and fast frame grabbers) allows the realisation of systems with high performance. New interesting applications of the technique in other fields (e.g. in biophysics) have recently been envisaged.

Tracking and vertex reconstruction in modern emulsion experiments

The analysis procedure of nuclear emulsions has radically changed with the realisation of high speed, fully automated scanning systems. Nuclear emulsion can now be considered as an analog data storage device from which the automated scanning system retrieves the data.

Benedict Cassen: the father of body organ imaging.

The invention of the radioisotope scanner by Benedict Cassen was seminal to the development of body organ imaging. Cassen assembled the first automated scanning system in 1950. It was a motor-driven scintillation detector coupled to a printer. The scanner was used to image the thyroid gland after the administration of radioiodine. Later, with the development of organ-specific radiopharmaceuticals the scanner was widely used during the late 50s until the early 70s to image the body organs.

Two-axis-scanning laser Doppler vibrometer for microstructure

The study and characterization of the dynamic behavior of micro-scale objects like e.g. AFM cantilever is essential to assess their performance. Laser Doppler vibrometers are suitable to achieve the measurement of dynamic parameters like displacement and vibration. Most of the time, the measurement can be done at one point of the object. As a point measurement is often not sufficient to fully understand the behavior of the microstructures, parameters must be determined at several points along the surface, and with more measurements, a more comprehensive study can be deduced from the analysis of these informations. Consequently, to evaluate the dynamic behavior of the entire microstructure, a highly accurate measurement system coupled to an automatic and fast scanning system is necessary. Presently, some systems do provide scanning and the scanning measurement is achieved either by using deflecting/rotating mirror or by using a two-axis stage that drives the tested sample under a stationary laser beam emitted out from a vibrometer. The positioning resolution and accuracy of mechanically driven scanning mirrors and moving stages limit the current techniques to the measurement of features with sizes in the millimeter range. In this paper, a two-axis-scanning Laser Doppler Vibrometer for micro-scale object dynamic behavior characterization is described. The system employs a two-axis acousto-optic deflectors and a telecentric lens to achieve high-precision and high-speed scanning. The newly developed vibrometer was used to measure the dynamic behavior of an entire AFM cantilever operated in free air. The 120 μm long, 25 μm wide micro-cantilever dynamic response was measured at different positions with 2 μm spatial resolution.

Study of the trapped field distributions and the microstructure for YBCO disks

The trapped field distributions on the surface of MTG YBCO disks were measured by a Hall probe automated scanning system, and exhibit a cone profile for sample A with levitation force up to 12.6 N/cm 2, whereas four peaks for sample B with 4.4 N/cm 2. However, c-axis orientations of two samples are all perpendicular to the sample surfaces according to the pole figure. For sample B, the boundaries between the sectors seem to be weak links, and the T c in the sector, which is very low, is higher than that in the boundary. The microstructure reveals that the agglomerates of non-superconductive phases occur in the boundary and the center for sample B, but do not occur in the sectors of sample B and nor in any part of sample A. So, it can be assumed that the agglomerates of non-superconductive phases in the boundary are mainly responsible for the low levitation force and trapped field with four peaks in distribution of sample B.

Performance of the Ultraheavy Collector of the Trek experiment

We report on the performance of the trek ultraheavy cosmic ray collector, an array of track-etch detectors which was deployed on the Russian space station Mir. Trek is the first space-based cosmic ray experiment to exploit the unique properties of the track-recording glass BP-1. We describe the systematic analysis of the Trek experiment, with emphasis on the calibration and verification of the Trek detectors, the automated scanning system used to locate and measure cosmic ray tracks, and the sources of dispersion in the measurement of cosmic ray charge. We find that the resolution for measurement of charge of ultraheavy galactic cosmic rays in Mir orbit will be 0.39–0.45 e in the absence of strong thermal variations or episodes of significantly elevated temperature. We also will discuss the extremely heavy cosmic ray composition observer (ECCO), a planned second generation BP-1 experiment, which would measure the age of galactic cosmic ray nuclei using the actinides as radioactive clocks.

Emission of relativistic heavy fragments at wide angles from the interaction of 58 GeV 16O ions with thick copper target

Relativistic projectile fragmentation has been studied with track detection methods. Heavy fragments produced in the interaction of 58 GeV 16O with thick copper target have been investigated using 10 cm thick stacks of PADC (sometimes called CR-39) nuclear track detectors placed at 25° with respect to the direction of the incoming beam. A computer-controlled automatic scanning system was employed to “trace” the etched damaged trails in respective detectors of the PADC stack. Heavy reaction products producing “through-tracks” in consecutive sheets of 0.82 mm of PADC detectors were observed. The spatial distribution of these tracks with end points at various depths have been recorded. After calibration it has been concluded that these “through-tracks” should be due to relativistic O, N and C. These fragments are emitted from the interaction of 58 GeV 16O ions with thick copper target, their actual number is very tiny. The differential angular cross-section for their formation was found to decrease with increasing angle with respect to the incident beam direction.

On the use of unshielded cables in ionization chamber dosimetry for total-skin electron therapy

The dosimetry of total-skin electron therapy (TSET) usually requires ionization chamber measurements in a large electron beam (up to ). Exposing the chamber's electric cable, its connector and part of the extension cable to the large electron beam will introduce unwanted electronic signals that may lead to inaccurate dosimetry results. While the best strategy to minimize the cable-induced electronic signal is to shield the cables and its connector from the primary electrons, as has been recommended by the AAPM Task Group Report 23 on TSET, cables without additional shielding are often used in TSET dosimetry measurements for logistic reasons, for example when an automatic scanning dosimetry is used. This paper systematically investigates the consequences and the acceptability of using an unshielded cable in ionization chamber dosimetry in a large TSET electron beam. In this paper, we separate cable-induced signals into two types. The type-I signal includes all charges induced which do not change sign upon switching the chamber polarity, and type II includes all those that do. The type-I signal is easily cancelled by the polarity averaging method. The type-II cable-induced signal is independent of the depth of the chamber in a phantom and its magnitude relative to the true signal determines the acceptability of a cable for use under unshielded conditions. Three different cables were evaluated in two different TSET beams in this investigation. For dosimetry near the depth of maximum buildup, the cable-induced dosimetry error was found to be less than 0.2% when the two-polarity averaging technique was applied. At greater depths, the relative dosimetry error was found to increase at a rate approximately equal to the inverse of the electron depth dose. Since the application of the two-polarity averaging technique requires a constant-irradiation condition, it was demonstrated that an additional error of up to 4% could be introduced if the unshielded cable's spatial configuration were altered during the two-polarity measurements. This suggests that automatic scanning systems with unshielded cables should not be used in TSET ionization chamber dosimetry. However, the data did show that an unshielded cable may be used in TSET ionization chamber dosimetry if the size of cable-induced error in a given TSET beam is pre-evaluated and the measurement is carefully conducted. When such an evaluation has not been performed, additional shielding should be applied to the cable being used, making measurements at multiple points difficult.

Biomedical concerns in wireless communications.

The last decade witnessed rapid development of new communication technologies and their broad acceptance at large. Digital wireless telephones are the most popular example of these technologies. There are two aspects of these technologies that are related to human health and therefore biomedical engineering. First, antennas of some devices are in close proximity to the user's head, thus possibly producing locally excessive energy deposition. Second, radiofrequency (RF) signals emitted are amplitude modulated at extremely low frequencies, potentially eliciting different biological effects from those of unmodulated RF radiation. Recent progress in addressing these two issues is reviewed in this article. Another area of research and concern not covered here is electromagnetic interference (EMI) with medical devices. Considerable research has been conducted on the development of a new method for numerical and experimental evaluation of the spatial distribution of the power deposition in tissue. Improved implantable electric field probes and automated scanning systems are presently available. With respect to numerical evaluation of electric fields in tissue, the finite difference time domain (FDTD) technique has proven to be a useful and accurate tool. These developments also are critical in view of the regulatory requirements now imposed on mobile/portable transmitters. Similarly, significant research effort on biological effects of modulated fields has been undertaken. Most of the studies are still in progress, and further research agendas have been proposed.

A search for νμ − ντ oscillation with CHORUS at CERN

A search for ν μ − ν τ oscillation with the CHORUS detector at CERN is in progress. The first data taking in 1994/1995 was successfully completed with 320 000 recorded ν μ CC events in the emulsion target and half of the second data taking period 1996/1997 has lead to 230 000 additional ν μ CC events. A pilot analysis of the 1994 data for the muonic τ decay search by using the fully automatic scanning systems, resulting in an upper limit sin 2(2 θ μτ ) ≤ 0.01 at 90% C.L. for large Δ m 2 , confirms that the proposed sensitivity (sin 2(2 θ μτ ) ≤ 3 × 10 −4) is within reach in two years.

Automated laser scanning based on orthogonal cross sections

To reversely engineer a clay model or industrial part, a laser scanner is often used to acquire surface data points, which must be processed to created a CAD model. Complete surface definition requires an operator to obtain a number of scans from various viewpoints and orientations. This introduces two difficulties to the reverse-engineering process: (1) the data are difficult to visualize, as scan lines appear at various angles, and (2) the surface is irregularly sampled, with large regions sampled by several scans, and occasionally a small region is missed completely (a result of the visualization problem). We have developed an automated scanning system to overcome these problems. The system utilizes an intermediate data model that consists of three orthogonal cross sections and is built from the triangulated scan data. The resultant model is easily visualized, which facilitates further interactive operation on the data. The system has been successful in autonomously modeling several typical industrial objects.

Ben cassen and the development of the rectilinear scanner

The development of the rectilinear scanner by Benedict Cassen was preceded by his successful fabrication of a directional scintillation detector probe. In 1950, Cassen assembled the first automated scanning system that was comprised of a motor driven scintillation detector coupled to a relay printer. The scanner was used to image thyroid glands after the administration of radioiodine. Initial studies that were performed at the West Los Angeles Veterans Administration Medical Center led to the extensive use of the scanning system for thyroid imaging during the early 1950s. Cassen's development of the rectilinear scanner was a defining event in the evolution of clinical nuclear medicine. In 1956, Kuhl and his colleagues developed a photographic attachment for the Cassen scanner that improved its sensitivity and resolution. With the development of organ-specific radiopharmaceuticals, a commercial model of this system was widely used during the late 1950s until the early 1970s to scan the major body organs. The decline of the rectilinear photoscanner began in 1973 with the advent of computed axial tomography.

Enhancing the sensitivity of CR-39 detectors to relativistic ions by etching in potassium and sodium hydroxides

We tested the feasibility of improving the sensitivity of CR-39 plastic detectors to relativistic ions by etching them in a mixture of 6.5N KOH and 6.25N NaOH. We examined the variation in sensitivity with fractional content of KOH in the mixed KOH + NaOH etchant at 60°C, by using a beam of 200 A GeV 32S at CERN SPS. We find that the detector response reaches a maximum when 6.5N KOH:6.25N NaOH ∼ 1:3 at 60°C. At the peak ratio, the detection threshold of CR-39 is one charge unit lower than those obtained from other etchants. Measurements made with an automated scanning system of etch pits developed in different etchants lead roughly to the same charge resolution σ Z = 0.10 ± 0.02 charge unit for one pair of etch pit measurements in the range 6 ≤ Z ≤ 16 at a sampling distance L s∼47–57 μm.

112 An automatic laser scanning system for mine tunnel surface characterisation: A.J. Jeffery, S. Durucan, J. Dennis, pp 531–534

112 An automatic laser scanning system for mine tunnel surface characterisation: A.J. Jeffery, S. Durucan, J. Dennis, pp 531–534