Beam Measurement System Research Articles

Modeling Research and Analysis of Multibeam Bathymetric Systems

This paper conducted research on the application of multi beam measurement system for underwater detection. Firstly, a mathematical model was established and determined for the coverage width of multi beam bathymetry and the overlap rate between adjacent bands; Secondly, based on the rectangular sea area to be measured, a mathematical model for the coverage width of multi beam bathymetry was established. Finally, in order to meet the requirement of 10% to 20% overlap between adjacent bands, a set of survey lines with the shortest measurement length and capable of fully covering the entire sea area to be measured was further studied and designed.

Vibroacoustic properties as a function of crystallinity changes in heat-treated Pinus radiata D. Don wood

ABSTRACT In this work, the relationship between relative crystallinity with mechanical and vibroacoustic properties of Pinus radiata wood, before and after heat treatment, was studied. Heat treatment was applied using a laboratory oven with a tray of liquid nitrogen inside to generate an oxygen-depleted atmosphere. To determine the vibrational properties, a free beam measurement system was used, and by means of an FTIR infrared imaging system, the relative crystallinity in the wood was determined. There were differences in properties between untreated and treated wood depending on the treatment conditions. In treated samples, the higher temperature and time produce an increase in the coefficient of sound radiation, a decrease in specific acoustic impedance and a non-significant change in the speed of sound. Moreover, the best degree of association between crystallinity and mechanical and vibrational properties was achieved at higher temperature and time, coinciding in turn with the conditions that allow an improvement in the vibrational properties of Pinus radiata wood. In general, the relationships described in this work contribute to the consideration that fast-growing species can have a more noble use through heat treatments.

Near-zero beam drift laser tracking and measurement system with two-stage compression structures.

This paper introduces a scheme of near-zero beam drift tracking technology with two-stage compression structures for the coordinate accuracy measurement of a laser tracker. The Galileo telescope system, with a magnification of 21.43, is designed to compress the beam drift in a dual-frequency interferometer. The azimuth and pitch of the beam drift are compressed to 2.41in. and 2.92in., and the compression rates are 95.0% and 91.9%, respectively. The improved four degrees of freedom position-sensitive detector system is used to further compress the beam drift. The peak-to-peak value of the beam drift is 0.9in. in the azimuth direction and 2.1in. in the pitch direction. The standard deviation of azimuth is within 0.15in, and the pitch is within 0.43in. The coordinate accuracy of the laser tracker can be improved 6.85 parts per million by simulation. The developed two-stage compression near-zero beam drift system can be used in the laser tracker to realize large-scale precision instrument geometric measurement.

Experiment for Evaluating a K-Band Space TWT Electron Beam

The electron beam of a K-band space traveling-wave tube (TWT) has been investigated in a beam measurement system in this article. The primary beam emitted from a Pierce-type electron gun is scanned by a Faraday cup probe, and the beam current density distribution and envelope are determined. The spent beam is also diagnosed with a novel retarding field energy analyzer (RFEA) by using the monopulse measurement method, and a comparison of velocity distribution between the experimental result and simulation is presented.

Feasibility Investigation for Online Elemental Monitoring of Iron and Steel Manufacturing Processes using Laser-Induced Breakdown Spectroscopy

The metallurgical industries are very important for social development. In order to improve the metallurgical techniques and quality of products, the real-time analysis and monitoring of iron and steel manufacturing processes are very significant. Laser-induced breakdown spectroscopy (LIBS) has been studied and applied for the contents measurement of iron and steel. In this paper, the remote open-path LIBS measurement was studied under different sample temperature, lens to target distance (LTD), sample angle conditions to clarify its online measurement features. The 3D profile measurement system of parallel laser beam fringes projection was also developed to measure the sample profile at different sample temperature. The measurement results demonstrated the robustness of remote open-path LIBS system and 3D profile measurement system. However, the correction is necessary to enhance the detection ability of LIBS online measurement. In order to improve the precision and accuracy of real-time elemental measurement, an innovative co-axial laser beam measurement system combining LIBS and 3D profile techniques is proposed to automatically adjust the focus unit and measure the sample components. The further study of this promising method will be developed for online application of iron and steel manufacturing processes.

Development of a microthrust balance and ion beam measurement system: Characterizing a dual-mode thruster for spacecraft

There is a rapid progression toward spacecraft miniaturization due to the prospect of reduced launch costs, the requirement for satellite constellations, and the integration of microelectromechanical systems (MEMS). Satellite propulsion is required for increased mission flexibility and orbital debris mitigation, but down-scaling of such devices has proven non-trivial. Some electrostatic thrusters are both challenging and promising given their increase in performance with small geometry, but the relatively low thrust produced through ion acceleration limits their mission applicability. For this reason, it may be desirable to produce thrusters that are able operate across a wide range of specific impulses, depending on maneuver time, thrust bit requirements, and several other factors that influence propulsion system selection. At RAPPEL, a bimodal thruster that can operate at high specific impulse with electrospray propulsion or high thrust using cold gas expansion has been developed. Inevitably, such a propulsion system comes with complications related to performance characterization. A novel and economical data acquisition system has been established to measure the performance of both modes in high vacuum. For the cold gas mode, a torsional thrust balance was built in-house to measure thrust levels between 1−15mN, and can be easily modified for lower ranges. The natural frequency of the thrust stand was measured to be 5.6Hz. The vacuum system sustained pressures below 5mbar while the cold gas nozzle operated, and 1.3×10−5mbar during electrospray operation. A 3-D printed linear cold gas nozzle was used to validate the thrust stand. Its thrust was close to 9mN at a mass flow rate of 20mg/s of nitrogen, producing a specific impulse of just under 45s. Due to the noise present in thrust stand measurements at the sub-mN force-level produced by electrosprays, the thrust stand was built to also accommodate a complementary ion beam current measurement system. The power processing unit, used to generate square-wave ±2500V signals using optodiodes, was built to operate a bipolar ionic liquid ion source (ILIS). The rise and fall times of the push/pull switch were close to 1ms and 30ms, respectively. The electrical power system used to operate the electrospray and measure its performance is examined in detail, followed by the results from validation of both data acquisition systems.

METU defocusing beamline project for the first SEE tests in Turkey and the test results from the METU-DBL preliminary setup

Abstract Space radiation can affect performance of electronic components during a satellite’s mission. In order to ensure reliable performance, these components must be tested under some types of radiation. Middle East Technical University - Defocusing Beam Line (METU-DBL) project aims to perform Single Event Effect (SEE) tests for space, HiLumi LHC, nuclear and other applications. ESA ESCC No. 25100 Standard Single Event Effect Test Method and Guidelines is considered for these SEE tests. Turkish Atomic Energy Authority (TAEA) has a cyclotron which can accelerate protons up to 30 MeV kinetic energy at the Proton Accelerator Facility (PAF) mainly for radioisotope production and for R&D purposes. According to the standard, the proton beam kinetic energy must be between 20 MeV and 200 MeV . While the proton energy is suitable for SEE tests, the beam size must be 15.40 cm × 21.55 cm and the flux must be between 1 0 5 p/cm 2 /s to at least 1 0 8 p/cm 2 /s according to the standard. The beam size at the entrance of the R&D room is mm-sized and the current is variable between 10 μ A and 1.2 mA. Therefore, a defocusing beam line has been designed to enlarge the beam size and reduce the flux. The beam line has three quadrupole magnets to enlarge the beam size and collimators and scattering foils are used for flux reduction. Currently, METU-DBL preliminary test setup, which was installed in the R&D room, enlarges the beam size with only two quadrupole magnets and it reduces the proton flux with a collimator. The final beam size is about 6 cm × 8 cm and the beam flux is ∼ 1 0 9 p/cm 2 /s. The first tests of electronic components were performed and the commissioning results from the beam measurement system are here presented.

Accurate numerical modeling of residual stress fields induced by laser shock peening

To improve the accuracy of numerical simulation of laser shock peening, a novel model is developed to predict residual stress distribution. An optical beam measurement system, a white light confocal displacement sensor, and other sensors are used to measure the laser shock peening parameters. Based on actual parameters, the model of shock wave pressure spatial distribution is established. Effects of key parameters, viz., overlapping rate and laser beam quality on residual stress distribution are analyzed by the proposed model. The influence mechanism of laser beam quality on residual stress hole is analyzed. Compared with conventional models, it is found that the proposed model has higher precision to predict residual stress distribution. The processing efficiency and strengthening effect can be improved by optimizing the overlapping rate and laser beam quality. The edge gradient of shock wave pressure reduces the intensity of the release wave convergence at the center, which can improve the uniformity of residual stress distribution. The proposed model can not only improve the accuracy of numerical simulation, but also provide guidance for optimizing the laser beam quality.

Probe Characterization in Terahertz Near-Field Beam Measurement Systems

The characterization of radiation patterns in the terahertz frequency range is usually performed with near-field beam measurement systems. In order to measure accurate patterns, the effects of the measurement probe must be compensated, especially at terahertz frequencies, because aperture sizes are very small and prone to fabrication errors. This paper presents detailed steps on how to characterize probe antennas at terahertz frequencies and confirms the possibility to extend probe compensation methods to this frequency range. This method has been applied to characterize the radiation patterns of probes for the 900 and 1400 GHz bands.

Measuring phased‐array antenna beampatterns with high dynamic range for the Murchison Widefield Array using 137 MHz ORBCOMM satellites

AbstractDetection of the fluctuations in a 21 cm line emission from neutral hydrogen during the Epoch of Reionization in thousand hour integrations poses stringent requirements on calibration and image quality, both of which necessitate accurate primary beam models. The Murchison Widefield Array (MWA) uses phased‐array antenna elements which maximize collecting area at the cost of complexity. To quantify their performance, we have developed a novel beam measurement system using the 137 MHz ORBCOMM satellite constellation and a reference dipole antenna. Using power ratio measurements, we measure the in situ beampattern of the MWA antenna tile relative to that of the reference antenna, canceling the variation of satellite flux or polarization with time. We employ angular averaging to mitigate multipath effects (ground scattering) and assess environmental systematics with a null experiment in which the MWA tile is replaced with a second‐reference dipole. We achieve beam measurements over 30 dB dynamic range in beam sensitivity over a large field of view (65% of the visible sky), far wider and deeper than drift scans through astronomical sources allow. We verify an analytic model of the MWA tile at this frequency within a few percent statistical scatter within the full width at half maximum. Toward the edges of the main lobe and in the sidelobes, we measure tens of percent systematic deviations. We compare these errors with those expected from known beamforming errors.

Experimental analysis of a new retarding field energy analyzer

In this paper, a new compact retarding field energy analyzer (RFEA) is designed for diagnosing electron beams of a K-band space travelling-wave tube (TWT). This analyzer has an aperture plate to sample electron beams and a cylindrical electrode to overcome the defocusing effects. The front end of the analyzer constructed as a multistage depression collector (MDC) structure is intended to shape the field to prevent electrons from being accelerated to escape. The direct-current (DC) beams of the K-band space TWTs with the removing MDC can be investigated on the beam measurement system. The current density distribution of DC beams is determined by the analyzer, while the anode voltage and helix voltage of the TWTs are 7000V and 6850V, respectively. The current curve’s slope effect due to the reflection of secondary electrons on the copper collector of the analyzer is discussed. The experimental analysis shows this RFEA has a good energy resolution to satisfy the requirement of beam measurement.

Development and application of bunch-by-bunch measurement system for BEPC II storage ring

A bunch-by-bunch beam measurement system is developed for BEPC II (Beijing Electron-Positron Collider II). In order to realize the bunch-by-bunch measurement, high isolation for signals of each bunch should be reached. The analogy signals are sampled bunch-by-bunch with high speed (500 MHz) ADCs. Bunch signals' separation and digital processing are done in Field Programmable Gate Array (FPGA). A resolution of about 4.5 μm for bunch-by-bunch measurement is reached. Bunch-by-bunch tunes and oscillation amplitudes are provided by the system. The system has become a powerful tool for BEPC II machine study. ©, 2015, Editorial Office of High Power Laser and Particle Beams. All right reserved.

Validation of C-Band Permittivity of Fresh Water using Periodic Jets

This letter presents the results of a free space experiment that validated the Meissner and Wentz model of fresh water permittivity at 13°C in C-Band. The experiment consisted of creating a periodic water jet array inside a focused beam measurement system. The focused beam system measures the radio frequency (RF) response to a finite array of free flowing water jets. The results of the experiment are compared to a one-dimensional Rigorous Coupled-Wave Analysis (RCWA) prediction for infinitely periodic cylinders of water. The consistency between the measured and predicted values appears to validate the permittivity of fresh water at 13°C in C-Band as predicted by the Meissner and Wentz model. This method for measuring and predicting the one-dimensional RCWA solver could be used to characterize properties of other liquids.

Electron cyclotron beam measurement system in the Large Helical Device

In order to evaluate the electron cyclotron (EC) heating power inside the Large Helical Device vacuum vessel and to investigate the physics of the interaction between the EC beam and the plasma, a direct measurement system for the EC beam transmitted through the plasma column was developed. The system consists of an EC beam target plate, which is made of isotropic graphite and faces against the EC beam through the plasma, and an IR camera for measuring the target plate temperature increase by the transmitted EC beam. This system is applicable to the high magnetic field (up to 2.75 T) and plasma density (up to 0.8 × 10(19) m(-3)). This system successfully evaluated the transmitted EC beam profile and the refraction.

Near-field beam pattern measurement of qualification model of ALMA band 8 (385–500 GHz) cartridge receiver

We have developed a near-field vector beam measurement system covering the range of frequencies from 385 to 500 GHz. The measurement set-up is capable of measurements with dynamic range exceeding 50 dB and amplitude and phase stability respectively of 0.1 dB/h and 1 degree/5 min at room temperature. Beam patterns of the ALMA band 8 corrugated horns and receiver optics block were measured at room temperature and lately compared with physical optics calculations obtained in the far-field. Both co-polar and cross-polar beam patterns of a qualification model of the ALMA band 8 cartridge cooled in a cartridge-test-cryostat have also been measured in the near-field as a detector of a submillimeter vector network analyzer. The measurements presented in this work refer to the lowest, middle and upper frequencies of band 8. The comparisons between software model and experimental measurements at these frequencies show good agreement down to −30 dB for the main polarization component. The cross-polarization level of the beam propagating through the receiver optics block was also characterized. We found that a cross-polarization level better than −28 dB can be achieved at all measured frequencies. The measured beam pattern of this receiver corresponds to efficiency of greater than 92% at the sub reflector (diameter of 750 mm) of the ALMA 12 m optics.

Submillimeter-Wave Phasor Beam-Pattern Measurement Based on Two-Stage Heterodyne Mixing With Unitary Harmonic Difference

A near-field phasor beam measurement system is developed for the characterization of heterodyne receiver optics at submillimeter-wave frequencies. The system synthesizes a pair of submillimeter-wave signals as the RF and local oscillator (LO) sources from common reference sources. The synthesized harmonic numbers of the RF and LO sources are arranged with difference by one, which makes this a new configuration with a unitary harmonic difference. The coherent RF and LO signal are down-converted by the receiver under test, then mixed with the microwave-frequency common reference signal to generate the second-order IF signal around 100 MHz for amplitude and phase comparison. The amplitude and phase fluctuation of the measurement system at 683 GHz is within plusmn0.2 dB and plusmn4deg in a 1-h period, respectively. The system dynamic range at 683 and 250 GHz can be as high as 43 and 47 dB, respectively. The system is then used to measure the receiver beam patterns at 683 and 250 GHz with different RF transmitting probe antennas.

S‐parameter measurements for oblique angles of incidence and Brewster angle studies for metamaterial samples

AbstractTo date, most numerical and experimental studies of metamaterials are limited to normally incident plane waves with the magnetic field parallel to the axis of the inductive structure. In this article, the reflected field response of three types of Split Ring Resonator (SRR) media are measured as a function of incident field polarization, angle of incidence and frequency, using an automated free space focused beam measurement system. The measured results are compared with simulated data generated using the experimentally retrieved complex permittivity and permeability tensors from normal incidence measurements. It is concluded that there is no classical Brewster angle (zero reflection for a given angle of incidence). However, we observe a reflection minimum for all angles of incidence in a small range of frequencies close to the plasmon frequency for all orientations of the SRRs for perpendicular polarization. This will indeed have important low observable applications. In parallel polarization, SRR media are transparent for small angles of incidence. For both polarizations, the effect of anisotropy becomes significant as the angle of incidence increases and a significant change in the reflected field is observed. Thus, considering the anisotropic nature of such metamaterials is important when designing applications. In this article, we also independently verify the assumed constitutive models and property retrieval using normal incidence measurements, using oblique incidence scans. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2619–2624, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21986

GafChromic® RTQA film for routine quality assurance of high-energy photon beams

Self-developing film offers many advantages over conventional radiographic verification film for routine radiotherapy quality assurance (QA). This paper presents results from an initial evaluation of a beam measurement system using GafChromic® RTQA film and a flatbed scanner. Variability and energy dependence of the film calibration and accuracy of scanner readout are investigated in the context of QA measurements. For exposures of film between 2 and 4 Gy, the system is adequate for measurement of beam dimensions, as in multi-leaf collimator (MLC) offsets and secondary jaw calibrations, where agreement with conventional film measurements is within 0.5 mm. However, the measurement of absolute dose is subject to errors of about 25 cGy.

On the Use of a Gaussian Beam to Isolate the Edge Scattering From a Plate of Finite Size

Free-space focused beam measurement systems are sometimes used to illuminate an edge of a sample under investigation while observing the scattering response. Typically, these kinds of measurements are performed to try to categorize the scattering from an edge of a material. Therefore, in this paper, a study is performed to obtain guidelines for the conditions under which the scattering of the beam is almost completely determined by the illuminated edge; that is, there is negligible scattering due to other physical structure immediately outside of the spot of the beam. The guidelines are obtained by comparing edge scattering due to a Gaussian beam incident on an infinitesimally thin, perfectly conducting plate with the edge scattering due to the same beam incident on an infinitesimally thin, perfectly conducting half-plane. The half-plane can be viewed as the ideal object for studying edge scattering because it contains only one edge. So the comparison between the plate and the half-plane determines the effect of the additional edges of the plate on the scattered field.

Scattering analysis of arbitrarily shaped cylinders in a focused beam system-oblique incidence case

The scattering from an arbitrarily shaped cylinder for the general oblique incident case is characterised by its induced field ratio (IFR) and its co-polarised and cross-polarised scattering patterns. The paper describes how a unique focused-beam measurement system is used to determine experimentally the scattering characteristics of an arbitrarily shaped cylinder for an obliquely incident plane wave. The fields of the transmitting and receiving antennas of the focused-beam measurement system are approximated by equivalent fundamental Gaussian beams. An analytical algorithm, based on computation of the coupling between the transmit and receive Gaussian beams of the focused beam measurement system and the scattered field of the cylinder, is used to determine the IFR and the co-polarised and cross-polarised scattering patterns of the cylinder. The experimental results obtained by this method for typical dielectric and metal cylinders agree well with the theoretical scattering characteristics computed numerically by the method of moments (MoM) and the finite element method (FEM).