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Mitigation of EC breakdown in the gyrotron transmission line of the ITER Collective Thomson Scattering diagnostic via a Split Biased Waveguide
摘要： In this paper we present the results of the R&D work that has been performed on avoiding electron cyclotron (EC) gas breakdown inside the launcher transmission line (TL) of the ITER collective Thomson scattering (CTS) diagnostic, due to encountering the fundamental EC resonance, which is located inside the port plug vacuum for the baseline ITER magnetic field scenario. If an EC breakdown occurs, this can lead to strong local absorption of the CTS gyrotron beam, as well as arcing inside the ITER vacuum vessel, which must be avoided. Due to the hostile, restrictive, and nuclear environment in ITER, it is not possible to implement the standard method for avoiding EC breakdown - a controlled atmosphere at the EC resonance. Instead, the CTS diagnostic will include a longitudinally-split electrically-biased corrugated waveguide (SBWG) in the launcher transmission line. The SBWG works by applying a transverse DC bias voltage across the two electrically-isolated waveguide halves, causing free electrons to diffuse out of the EC resonant region before they can cause an electron-impact ionisation-avalanche, and thus an EC breakdown. Due to insufficient experimental facilities, the functionality of the SBWG is validated through Monte Carlo electron modelling.
关键词： Interaction of radiation with matter,Nuclear instruments and methods for hot plasma diagnostics,Overall mechanics design (support structures and materials, vibration analysis etc),Detector design and construction technologies and materials
更新于2025-09-12 10:27:22
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Coupled FPEDs using springs for broadband energy harvesting
摘要： In this paper, ?exible piezoelectric devices (FPEDs) connected by springs are discussed with the aim of improving operational bandwidth of an energy harvesting system. A theoretical method, based on beam theory, electromechanical coupling and the transfer matrix method, is presented for calculating displacement and voltage responses. Validity of the presented method is discussed by comparison with experimental results, which are obtained from coupled FPEDs excited by a shaker. The e?ects on system behaviour of attaching springs is discussed based on both the presented method and experimental results.
关键词： ?exible piezoelectric device,forced vibration,theoretical analysis method,engine vibration,Piezoelectric ?lm,renewable energy
更新于2025-09-11 14:15:04
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Proceedings [EAGE Publications BV 76th EAGE Conference and Exhibition 2014 - Amsterdam, Netherlands (2014.06.16-2014.06.19)] Proceedings 76th EAGE Conference and Exhibition 2014 - Fundamentals of Vibration Sensing with Distributed Fibre Optic Sensors through Downscaled Experiments
摘要： In the past few years the Distributed Vibration Sensing of fibre optic sensors (also called Distributed Acoustic Sensing) has gained great interest in geophysics, despite the fundamentals of the measurement being poorly understood. The technology offers immense improvement in terms of efficiency when compared with current geophysical methods and also could be preferred for applications such as permanent reservoir monitoring. We present a method for downscaled experimentation that enabled us to define the fundamentals of the optical fibre measurement. We show seismic data that were recorded simultaneously by both the fibre optical interferometer and conventional geophones, thus enabling the comparison of sensor performance. We present results focused on wave-polarity sensitivity and the directionality of fibre measurements. The current interrogation method of optical fibre cables cannot distinguish between wavefields coming from opposite azimuthal directions, which can be an issue in certain applications where the identification of up-going and down-going wavefields is essential. Observations are also presented that describe the relationship between the velocity signal that is measured using a geophone array and the phase difference measurement from the fibre optic sensing system.
关键词： directionality,Distributed Vibration Sensing,Distributed Acoustic Sensing,optical fibre measurement,geophones,wave-polarity sensitivity,seismic data,fibre optic sensors,geophysics
更新于2025-09-11 14:15:04
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Modeling and Experimental Study of the Vibration Effects in Urban Free-Space Optical Communication Systems
摘要： Free-space optical (FSO) communication, considered as a last-mile technology, is widely used in many urban scenarios. However, the performance of urban free-space optical (UFSO) communication systems fades in the presence of system vibration caused by many factors in the chaotic urban environment. In this paper, we develop a dedicated indoor vibration platform and atmospheric turbulence to estimate the Bifurcated-Gaussian (B-G) distribution model of the receiver optical power under different vibration levels and link distances using nonlinear iteration method. Mean square error (MSE) and coef?cient of determination (R2) metrics have been used to show a good agreement between the PDFs of the experimental data with the resulting B-G distribution model. Besides, the UFSO channel under the effects of both vibration and atmospheric turbulence is also explored under three atmospheric turbulence conditions. Our proposed B-G distribution model describes the vibrating UFSO channels properly and can easily help to perform and evaluate the link performance of UFSO systems, e.g., bit-error-rate (BER), outage probability. Furthermore, this work paves the way for constructing completed auxiliary control subsystems for robust UFSO links and contributes to more extensive optical communication scenarios, such as underwater optical communication, etc.
关键词： Urban free-space optical (UFSO) communication,probability density function (PDF),Bifurcated-Gaussian distribution,vibration analysis,received optical power
更新于2025-09-11 14:15:04
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Laser self-mixing interferometry for micro-vibration measurement based on inverse Hilbert transform
摘要： A novel micro-vibration reconstruction method based on inverse Hilbert transform is presented. By inversing either side of the SMI signal after Hilbert transform, micro-vibration can be reconstructed quickly and conveniently. In the paper, the principle of inverse Hilbert transform algorithm is studied. And, the effectiveness of the method is verified through simulated signals, and several experiments are carried out, including the self-mixing signal affected by speckle effect. The experimental results show that the external cavity phase can be rapidly extracted by inverse Hilbert transform algorithm, and the relative error is no more than 7%.
关键词： Micro-vibration reconstruction,Phase extraction,Self-mixing interferometry,Semiconductor laser diode
更新于2025-09-11 14:15:04
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An investigation into the influence of mass inertia using primary calibration of the back-to-back accelerometer by laser interferometry
摘要： In this paper, we discuss the effects of loading mass deformation and contact stiffness by giving various mass loadings in high-frequency primary calibration of the back-to-back accelerometer up to 20 kHz. The experimental contradiction of sensitivity and phase shift with respect to the mass loading effect described in the international standard document ISO 16063-11 indicates that there is no deformation of the loading mass, but only the effect of contact stiffness. In order to explain the validity of the contact stiffness according to the experimental results, it was verified by using a physical model and the finite element method with COMSOL software. As a result, the screw-joint function of the screw in the software agreed with the experimental result concerning the contact stiffness.
关键词： primary calibration,mass inertia,ISO 16063-11,back-to-back accelerometer,vibration,dummy mass
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Las Vegas, NV, USA (2019.5.28-2019.5.31)] 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Assessment of Accelerometer Versus LASER for Board Level Vibration Measurements
摘要： The ongoing trend to deploy ICs in more complex and harsher applications, entails precise evaluation of solder joint reliability of components subjected to vibration loads. For this, a good understanding of the PCB vibrational motion during a board level vibration test is essential. This can only be achieved by a well characterized vibration test setup. The vibration motion can be recorded by using a contact-based measurement approach, using an accelerometer, or a contactless measurement configuration, i.e. using a Laser Doppler Vibrometer (LDV). This paper evaluates both measurement techniques by recording the PCB dynamic response, i.e. the resonance frequency and peak-to-peak displacement, in a board level vibration test set up. Bare and assembled printed circuit boards (PCBs) are investigated using different PCB form factors and package outlines (Wafer Level Chip Scale Package (WLCSP) and Ball Grid Array (BGA)), showing that LDV enables better lateral resolution and a more accurate measurement solution. Especially when the weight of the accelerometer cannot be neglected compared to the weight of the component on the PCB. An accelerometer is shown to perturb the PCB vibration motion. It is found that depending upon the test objectives and PCB electronic system involved, both techniques can be used as complementary to one another. The accelerometer weight may give rise to substantial modification of vibration response which can be used to simulate the presence of a component on a bare PCB. In addition, both methods are expected to recognize the same trends when e.g. studying the environmental impact during vibration tests. Finally, the experimental observations are also confirmed using a Finite Element Model (FEM).
关键词： board level reliability,LASER Doppler Vibrometer,Wafer Level Chip Scale Package,vibration test,modal analysis,PCB dynamic response
更新于2025-09-11 14:15:04
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Electric Arc Coverage Indicator for AC Furnaces Using a Laser Vibrometer and Neural Networks
摘要： A common operational practice in the electric arc furnace (EAF) consist in keeping the electric arc covered with metallic scrap or foaming slag, this is to prevent that the refractory and water cooled panels absorb part of the radiation that should heat the steel. The radiation not absorbed by the steel is not only a waste of energy and money, it is also a latent danger because it damages the walls of the furnace. Today furnace operators use their experience and common sense to predict the degree of coverage of the arc and decide the electrical power the EAF can safely absorb along the process, without damaging the walls and increase the risk of an internal explosion. However, this method is subjective and might leads to human errors. This research was aimed to find robust indicators of arc coverage that could assist the furnace operator in deciding the amount of electrical power the furnace can safely absorb. During this research, it was found a strong relation between the vibrations of the furnace’s shell and the level of coverage of the electric arc. The vibration measurements were done with a laser and the vibration signal was processed using an Artificial Neural Network (ANN) implemented in LabVIEW?. The ANN was trained to emulate the intelligence and knowledge of a very productive and safe furnace operator. Excellent field results were obtained with this implementation and are reported in this paper.
关键词： EAF vibration,arc coverage indicator,neural networks,EAF,electric arc furnace,laser vibrometer
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - The Photonic Guitar Pickup: A High-Sensitivity, High-Bandwidth Fiber Strain Sensor
摘要： The photonic guitar pickup: a high-sensitivity, high-bandwidth fiber strain sensor. Fiber-strain sensors have found numerous applications from structural health monitoring for vibrations, to pressure and temperature sensing. Many of these sensors exploit the strain-sensitivity of the reflection wavelength of fiber-bragg gratings, (cid:83)-shifted gratings or other waveguide devices. The strain is typically inferred from a change of reflected or transmitted light intensity. Light intensity measurements are not very robust and have an inherently limited accuracy. We propose that a frequency-based strain measurements using fiber Fabry-Perot (FFP) cavities provide not only superior sensitivity but also retain a very high measurement bandwidth. Here, we present a fiber optic vibration sensor based on an FFP cavity, which consists of a matched pair of 23 dB fiber Bragg gratings coupled to a custom-built signal processing circuit. The wavelength of a laser diode is locked to one of the many cavity resonances using the Pound–Drever–Hall scheme. We demonstrate that such a strain sensor has an ultrawide dynamic sensing range, from less than 1 Hz to clinical ultrasound frequencies near 6 MHz. Its linear sensitivity range extends from below 1 n(cid:72) to 2 (cid:80)(cid:72), and its dynamic response limit is as high as 12 m(cid:72)/s. To demonstrate the high fidelity of the strain measurements we attached the FFP cavity sensor to the top plate of an acoustic guitar and recorded several melodies. As expected the sensor system was largely immune to noise arising from optical intensity fluctuations. We made distortion-free audio recordings of musical pieces from infrasound (~8 Hz) to 30 kHz with a 50 dB dynamic range in acoustic power. The remaining noise in our measurements arises from electronic sources and not optical sources, giving hope that future developments may be able to further increase the dynamic range of the measurements, if needed. In separate experiments the same sensor was affixed to the rim of a wineglass and to the side of a steel cantilever to monitor the (photo-)acoustic response of these mechanical resonators to periodic photo-excitation. We found, for example, that the limit of detection for orthophosphate through the photoacoustic excitation of the respective molybdenum-blue complex was below 2 ppm. Finally, the sensor was embedded in tissue phantoms to validate that it accurately responds to low frequencies (heart beat) and high frequencies (ultrasound pulse). In its most recent version the laser driver and the PDH circuit are addressed through a Raspberry-Pi microcontroller, making the sensor system very compact and relatively inexpensive. We propose that sensor systems based on PDH-interrogated FFP-sensor heads are robust and versatile for a large variety of monitoring applications.
关键词： Fabry-Perot cavity,vibration sensor,dynamic range,Pound–Drever–Hall scheme,fiber strain sensor
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Twin Multicore Fiber Interferometers for Precision Sensing
摘要： Multicore fiber (MCF) sensors is an emerging research field. MCFs provide new alternatives for the development of innovative sensing devices whose performance cannot be achieved with conventional optical fibers. In general, MCFs have diameters similar to that of a standard single mode fiber (SMF) and have multiple individual cores sharing a common cladding. So far, a number of sensors based on MCF have been reported. Our group, for example, has reported different sensors based on single MCF interferometers that consist of a piece of MCF spliced to SMF [1,2]. One key issue of such sensors is the difficulty of discriminating the target parameter (measurand) from unwanted external perturbations that may be present during the use of the sensor. To address this issue, here, we introduce an innovative architecture that consists of two identical (twin) MCF interferometers in series that are interrogated in reflection mode, see Fig. 1. Our architecture has important advantages. As there are two MCF interferometers, one can be used as a reference or filter and the other as a sensor [3]. The signal of our twin MCF interferometers is the multiplication of individual reflection spectra. Consequently, their reflection exhibits a single narrow peak whose position in wavelength is easy to track. We have observed that periodic bending (vibrations) in one them resulted in prominent shifts in the reflection spectrum.
关键词： precision sensing,vibration sensors,interferometers,Multicore fiber,bending sensors
更新于2025-09-11 14:15:04