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Experimental study of core MHD behavior and a novel algorithm for rational surface detection based on profile reflectometry in EAST
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作者 叶凯萱 周振 +20 位作者 张涛 马九阳 王嵎民 李恭顺 耿康宁 吴茗甫 文斐 黄佳 张洋 邵林明 杨书琪 钟富彬 高善露 喻琳 周子强 向皓明 韩翔 张寿彪 李国强 高翔 the EAST Team 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第3期66-75,共10页
Microwave reflectometry is a powerful diagnostic that can measure the density profile and localized turbulence with high spatial and temporal resolution and will be used in ITER,so understanding the influence of plasm... Microwave reflectometry is a powerful diagnostic that can measure the density profile and localized turbulence with high spatial and temporal resolution and will be used in ITER,so understanding the influence of plasma perturbations on the reflect signal is important.The characteristics of the reflect signal from profile reflectometry,the time-of-flight(TOF)signal associated with the MHD instabilities,are investigated in EAST.Using a 1D full-wave simulation code by the Finite-DifferenceTime-Domain(FDTD)method,it is well validated that the local density flattening could induce the discontinuity of the simulated TOF signal and an obvious change of reflect amplitude.Experimental TOF signals under different types of MHD instabilities(sawtooth,sawtooth precursors and tearing mode)are studied in detail and show agreement with the simulation.Two new improved algorithms for detecting and localizing the radial positions of the low-order rational surface,the cross-correlation and gradient threshold(CGT)method and the 2D convolutional neural network approach(CNN)are presented for the first time.It is concluded that TOF signal analysis from profile reflectometry can provide a straightforward and localized measurement of the plasma perturbation from the edge to the core simultaneously and may be a complement or correction to the q-profile control,which will be beneficial for the advanced tokamak operation. 展开更多
关键词 MHD instabilities profile reflectometry rational surface detection convolutional neural network(CNN) EAST tokamak
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Observation of Doppler shift f_(D) modulated by the internal kink mode using conventional reflectometry in the EAST tokamak
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作者 李恭顺 张涛 +18 位作者 耿康宁 文斐 叶凯萱 徐立清 朱翔 张学习 钟富彬 周振 杨书琪 周子强 喻琳 兰婷 王守信 提昂 张寿彪 刘海庆 李国强 高翔 the EAST Team 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第3期1-9,共9页
In this paper we present a new experimental observation using a conventional reflectometry technique,poloidal correlation reflectometry(PCR),in the Experimental Advanced Superconducting Tokamak(EAST).The turbulence sp... In this paper we present a new experimental observation using a conventional reflectometry technique,poloidal correlation reflectometry(PCR),in the Experimental Advanced Superconducting Tokamak(EAST).The turbulence spectrum detected by the PCR system exhibits an asymmetry and induced Doppler shift f_(D)during the internal kink mode(IKM)rotation phase.This Doppler shift f_(D)is the target measurement of Doppler reflectometry,but captured by conventional reflectometry.Results show that the Doppler shift f_(D)is modulated by the periodic changes in the effective angle between the probing wave and cutoff layer normal,but not by plasma turbulence.The fishbone mode and saturated long-lived mode are typical IKMs,and this modulation phenomenon is observed in both cases.Moreover,the value of the Doppler shift f_(D)is positively correlated with the amplitude of the IKM,even when the latter is small.However,the positive and negative frequency components of the Doppler shift f_(D)can be asymmetric,which is related to the plasma configuration.A simulated analysis is performed by ray tracing to verify these observations.These results establish a clear link between f_(D)and IKM rotation,and are helpful for studying the characteristics of IKM and related physical phenomena. 展开更多
关键词 microwave reflectometry Doppler shift internal kink mode
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Investigation of phase modulation and propagation-route effect from unmatched large-scale structures for Doppler reflectometry measurement through 2D full-wave modeling
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作者 冯喜 刘阿娣 +20 位作者 周楚 邹晓岚 庄革 王守信 王明远 刘海庆 丁卫星 张寿彪 吴木泉 朱翔 郝保龙 张津 刘朝阳 季佳旭 仲小明 刘深 谢锦林 林晓东 黄建军 高翔 万元熙 《Plasma Science and Technology》 SCIE EI CAS CSCD 2023年第11期55-65,共11页
To interpret the common symmetric peaks caused by the large-scale structure in the complex S(f)spectrum from the heterodyne Doppler reflectometry(DR)measurement in EAST,a 2D circular-shaped O-mode full-wave model base... To interpret the common symmetric peaks caused by the large-scale structure in the complex S(f)spectrum from the heterodyne Doppler reflectometry(DR)measurement in EAST,a 2D circular-shaped O-mode full-wave model based on the finite-difference time-domain method is built.The scattering characteristics and the influences on the DR signal from various scales are investigated.When the structure is located around the cutoff layer,a moving radial or poloidal large-scale structure k_(θ)k_(θ),match(k_(θ),match is the theoretic wavenumber of Bragg scattering)could both generate an oscillation phase term called‘phase modulation’,and symmetrical peaks in the complex S(f)spectrum.It was found that the image-rejection ratio A_(−1)/A_(+1)(A_(±1)represents the amplitudes of±1 order modulation peaks)could be a feasible indicator for experiment comparison.In the case when the structure is near the cutoff layer with the same arrangement as the experiment for the edge DR channel,the curve of A_(−1)/A_(+1)versus kθcan be divided into three regions,weak asymmetrical range with k_(θ)/k_(0)0.15(k_(0)is the vacuum wavenumber),harmonics range with 0.15k_(θ)/k_(0)0.4,and Bragg scattering range of 0.4k_(θ)/k_(0)0.7.In the case when the structure is located away from the cutoff layer,the final complex S(f)spectrum is the simple superimposing of modulation and Bragg scattering,and the modulation peaks have an amplitude response nearly proportional to the local density fluctuation,called the‘propagationroute effect’.Under the H-mode experiment arrangement for the core DR,a critical fluctuation amplitude Amp(n_(e,Mod.@route))/Amp(n_(e,Tur.@MSA)∼1.3–4.1(Amp(n_(e,Mod.@route))refers to the pedestal large-scale structure amplitude and Amp(ne,Tur.@MSA)refers to turbulence amplitude at the main scattering area)is needed for the structure in the pedestal to be observed by the core DR measurement.The simulations are well consistent with the experimental results.These effects need to be carefully considered during the DR signal analyses as the injecting beam passes through the plasma region with large-scale structures. 展开更多
关键词 Doppler reflectometry full-wave simulation propagation-route effect
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Reconstruction of hollow areas in density profiles from frequency swept reflectometry
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作者 Rennan B MORALES Stéphane HEURAUX +3 位作者 Roland SABOT Sébastien HACQUIN Frédéric CLAIRET the Tore Supra Team 《Plasma Science and Technology》 SCIE EI CAS CSCD 2020年第6期32-40,共9页
The standard density profile reconstruction techniques are based on the WKB approximation of the probing wave’s phase,making them unable to properly reconstruct blind areas in the cut-off frequency profile.The recons... The standard density profile reconstruction techniques are based on the WKB approximation of the probing wave’s phase,making them unable to properly reconstruct blind areas in the cut-off frequency profile.The reconstruction suffers a significant immediate error that is not rapidly damped.It is demonstrated that even though no reflections occur inside the hollow region causing the blind area,the higher probing frequencies that propagate through it carry information that can be used to estimate its properties.The usually ignored full-wave effects were investigated with the use of full-wave simulations in 1 D,with special attention paid to the frequency band where they are dominant.A database of perturbation signals was simulated onfive-dimensions of parameters and an application of the database inversion was demonstrated for a magnetic island in a Tore Supra discharge.The new adapted reconstruction scheme improved the description of the density profile inside the hollow region and also along 10 cm after it. 展开更多
关键词 FM-CW reflectometry profile reconstruction reflectometry density profile hollow profile blind area
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Influence of laser linewidth on performance of Brillouin optical time domain reflectometry 被引量:5
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作者 郝蕴琦 叶青 +2 位作者 潘政清 蔡海文 瞿荣辉 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第7期257-261,共5页
The effects of optical sources with different laser linewidths on Brillouin optical time domain reflectometry (BOTDR) are investigated numerically and experimentally. Simulation results show that the spectral linewi... The effects of optical sources with different laser linewidths on Brillouin optical time domain reflectometry (BOTDR) are investigated numerically and experimentally. Simulation results show that the spectral linewidth of spontaneous Brillouin scattering remains almost constant when the laser linewidth is less than 1 MHz at the same pulse width; otherwise, it increases sharply. A comparison between a fiber laser (FL) with 4-kHz linewidth at 3 dB and a distributed feedback (DFB) laser with 3-MHz linewidth is made experimentally. When a constant laser power is launched into the sensing fiber, the fitting linewidths of the beat signals (backscattered Brillouin light and local oscillator (LO)) is about 5 MHz wider for the DFB laser than for the FL and the intensity of the beat signal is about a half. Furthermore, the frequency fluctuation in the long sensing fiber is lower for the FL source, yielding about 2 MHz less than that of the DFB laser, indicating higher temperature/strain resolution. The experimental results are in good agreement with the numerical simulations. 展开更多
关键词 Brillouin optical time domain reflectometry (BOTDR) laser linewidth distributed feedback laser fiber laser
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Digital coherent detection research on Brillouin optical time domain reflectometry with simplex pulse codes 被引量:7
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作者 郝蕴琦 叶青 +2 位作者 潘政清 蔡海文 瞿荣辉 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第11期253-256,共4页
The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry (BOTDR), where the simplex pulse codes are applied in the sensi... The digital coherent detection technique has been investigated without any frequency-scanning device in the Brillouin optical time domain reflectometry (BOTDR), where the simplex pulse codes are applied in the sensing system. The time domain signal of every code sequence is collected by the data acquisition card (DAQ). A shift-averaging technique is applied in the frequency domain for the reason that the local oscillator (LO) in the coherent detection is fix-frequency deviated from the primary source. With the 31-bit simplex code, the signal-to-noise ratio (SNR) has 3.5-dB enhancement with the same single pulse traces, accordant with the theoretical analysis. The frequency fluctuation for simplex codes is 14.01 MHz less than that for a single pulse as to 4-m spatial resolution. The results are believed to be beneficial for the BOTDR performance improvement. 展开更多
关键词 Brillouin optical time domain reflectometry digital coherent detection simplex pulse codes signal-to-noise ratio
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Density Profile and Fluctuation Measurements by Microwave Reflectometry on EAST 被引量:2
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作者 张寿彪 高翔 +7 位作者 凌必利 王嵎民 张涛 韩翔 刘子奚 布景亮 李建刚 EAST team 《Plasma Science and Technology》 SCIE EI CAS CSCD 2014年第4期311-315,共5页
A microwave reflectometry system operating in the V-band frequency with extraor- dinary mode polarization has been developed on the EAST tokamak. The reflectometry system, using a voltage-controlled oscillator (VCO)... A microwave reflectometry system operating in the V-band frequency with extraor- dinary mode polarization has been developed on the EAST tokamak. The reflectometry system, using a voltage-controlled oscillator (VCO) source driven by an arbitrary waveform generator with high temporal resolution, can operate for the density profile measurement. The result of the bench test shows that the output frequency of the VCO has a linear dependence on time. The dispersion of reflectometry system is determined and reported in this paper. The evolution of a pedestal density profile during the L-H transition is observed by the reflectometry in H-mode discharges on EAST tokamak. A frequency synthesizer is used to replace the VCO as microwave source for density fluctuation measurements. The level of density fluctuation in the pedestal shows an abrupt decrease when the plasma enters into H-mode. A coherent mode with a frequency of about 100 kHz is observed and the mode frequency decreases gradually as the pedestal evolves. 展开更多
关键词 microwave reflectometry PEDESTAL density fluctuation EAST
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Two-dimensional distributed strain sensing with an Archimedean spiral arrangement in optical frequency domain reflectometry 被引量:1
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作者 Yamei Guo Zhenyang Ding +3 位作者 Kun Liu Junfeng Jiang Chenhuan Wang Tiegen Liu 《Nanotechnology and Precision Engineering》 EI CAS CSCD 2018年第3期187-190,共4页
We demonstrate a distributed two-dimensional(2D)strain-sensing system in optical frequency domain reflectometry(OFDR)with an Archimedean spiral arrangement of the sensing fiber.The Archimedean spiral describes a simpl... We demonstrate a distributed two-dimensional(2D)strain-sensing system in optical frequency domain reflectometry(OFDR)with an Archimedean spiral arrangement of the sensing fiber.The Archimedean spiral describes a simple relationship between the radial radius and polar angle,such that each circle(the polar angle from0 to 2π)can sense the 2D strain in all directions.The strain between two adjacent circles can also be easily obtained because an Archimedean spiral facilitates sensing of every angle covering the full 2D range.Based on the mathematical relation of Archimedean spirals,we deduce the relationship between the one-dimensional position of the sensing fiber and 2D distribution in polar coordinates.The results of the experiment show that an Archimedean spiral arrangement system can achieve 2D strain sensing with different strain load angles. 展开更多
关键词 OPTICAL frequency DOMAIN reflectometry (OFDR) ARCHIMEDEAN SPIRAL DISTRIBUTED OPTICAL fiber sensing
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Nonlinearity-Compensation-Free Optical Frequency Domain Reflectometry Based on Electrically-Controlled Optical Frequency Sweep 被引量:1
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作者 Fan Yang Ling-Jie Zhang +2 位作者 Zhi-Yao Zhang Xiao-Jun Zhou Yong Liu 《Journal of Electronic Science and Technology》 CAS CSCD 2021年第1期89-96,共8页
A nonlinearity-compensation-free optical frequency domain reflectometry(OFDR)scheme is proposed and experimentally demonstrated based on the electrically-controlled optical frequency sweep.In the proposed scheme,the l... A nonlinearity-compensation-free optical frequency domain reflectometry(OFDR)scheme is proposed and experimentally demonstrated based on the electrically-controlled optical frequency sweep.In the proposed scheme,the linear frequency sweep light is generated by propagating an ultra-narrow-linewidth continuous-wave(CW)light through an electro-optic frequency shifter which consists of a dual-parallel Mach-Zehnder modulator(DPMZM)and an electronic 90°hybrid,where the electro-optic frequency shifter is driven by a linear frequency modulated signal generated by a direct digital synthesizer(DDS).Experimental results show that the spatial resolution and signal-to-noise ratio(SNR)of the proposed OFDR scheme without the nonlinear phase compensation are comparable to those of OFDR employing a commercial tunable laser source(TLS),an auxiliary interferometer,and a software-based nonlinear phase compensation method.The proposed OFDR scheme is helpful to reduce the complexity of the optical structure and eliminate the difficulty of developing the nonlinear phase compensation algorithm. 展开更多
关键词 Dual-parallel Mach-Zehnder modulator(DPMZM) electro-optic frequency shifter optical fiber sensor optical frequency domain reflectometry(OFDR)
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The investigation of quasi coherent mode on EAST using Doppler reflectometry
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作者 Jiaxu JI Adi LIU +17 位作者 Chu ZHOU Xi FENG Shouxin WANG Haiqing LIU Hailin ZHAO Yong LIU Jin ZHANG Zhaoyang LIU Xiaoming ZHONG Hongrui FAN Ge ZHUANG Jinlin XIE Tao LAN Wenzhe MAO Weixing DING Hong LI Zixi LIU Wandong LIU 《Plasma Science and Technology》 SCIE EI CAS CSCD 2021年第9期60-64,共5页
An electrostatic Quasi coherent mode has been observed in density fluctuations and perpendicular velocity fluctuations with the frequency range of 3–80 k Hz on the Experimental Advanced Superconducting Tokamak using ... An electrostatic Quasi coherent mode has been observed in density fluctuations and perpendicular velocity fluctuations with the frequency range of 3–80 k Hz on the Experimental Advanced Superconducting Tokamak using multi-channel Doppler reflectometry.It appears in the edge localized mode(ELM)-free period after L-H transition or in the inter-ELM period.The mode rotates almost together with the plasma with the poloidal wave number around 0.6cm-1 and its frequency chirps with plasma poloidal velocity.The mode can exist in a large radial coverage(ρ=0.75–0.98),and peaks near the top of pedestal,suggesting that it might be excited in the steep gradient pedestal region,and spread into the core area. 展开更多
关键词 H-MODE TURBULENCE quasi coherent mode doppler reflectometry
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Design of Q-band FMCW reflectometry for electron density profile measurement on the Joint TEXT tokamak
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作者 万凌寒 杨州军 +4 位作者 周若冰 潘晓明 张弛 谢先立 阮博文 《Plasma Science and Technology》 SCIE EI CAS CSCD 2017年第2期101-107,共7页
The Q-band (33-50 GHz) fast sweep frequency modulated continuous wave (FMCW) reflectometry has been recently developed for electron density profile measurement on the Joint TEXT tokamak. It operates in ordinary mo... The Q-band (33-50 GHz) fast sweep frequency modulated continuous wave (FMCW) reflectometry has been recently developed for electron density profile measurement on the Joint TEXT tokamak. It operates in ordinary mode (O-mode) with a 20 μs sweeping period, covering the density range from 1 × 10^19m 3 to 3 × 10^19m-3. On the bench test, a Yttrium Iron Garnet (YIG) filter is used for the dynamic calibration of the voltage controlled oscillator (VCO) to obtain a linear frequency sweep. Besides, the use of a power combiner helps to improve the sideband suppression level of the single side-band modulator (SSBM). The reconstructed density profiles are presented, which demonstrate the capability of the reflectometry. 展开更多
关键词 reflectometry density plasma DIAGNOSTICS
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Fullwave Doppler reflectometry simulations for density turbulence spectra in ASDEX Upgrade using GENE and IPF-FD3D
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作者 C LECHTE G D CONWAY +2 位作者 TGÖRLER T HAPPEL the ASDEX Upgrade Team 《Plasma Science and Technology》 SCIE EI CAS CSCD 2020年第6期41-48,共8页
Doppler reflectometry is an important microwave diagnostic for turbulent fusion plasmas.A microwave beam is scattered off density fluctuations,with wavenumbers according to incident frequency and relative direction.Th... Doppler reflectometry is an important microwave diagnostic for turbulent fusion plasmas.A microwave beam is scattered off density fluctuations,with wavenumbers according to incident frequency and relative direction.This way,a density fluctuation spectrum is measured.However,the correspondence between fluctuation power and scattered microwave power is strongly nonlinear.Studying these processes numerically therefore requires fullwave simulations(IPF-FD3 D),with density fluctuations supplied by a separate plasma turbulence code(GENE).Earlier such attempts suffered from the low number of data points in the‘interesting’part of the spectrum,where a power law had to be fitted to 4 or 5 points.This has been overcome with recent simulations,which now show a much better agreement with experimental data. 展开更多
关键词 plasma diagnostics Doppler reflectometry SIMULATION microwaves
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Microwave Reflectometry for Plasma Density Profile Measurements on HL-2A Tokamak
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作者 肖维文 刘泽田 +2 位作者 丁玄同 石中兵 Vladimir ZHURAVLEV 《Plasma Science and Technology》 SCIE EI CAS CSCD 2006年第2期133-136,共4页
A modulated microwave reflectometry has been successfully developed on HL-2A, which can be used to measure the plasma density profile with time-delay method. This microwave reflectometry has two frequency ranges (26.... A modulated microwave reflectometry has been successfully developed on HL-2A, which can be used to measure the plasma density profile with time-delay method. This microwave reflectometry has two frequency ranges (26.5 to 40 GHz and 40 to 60 GHz) and it is suitable for measuring the plasma density ranging from 0.8×10^13 cm^-3 to 4.5×10^13 cm^-3. The temporal resolution is i ms and the spatial resolution is about 1 cm. This paper will present the basic principle of the microwave reflectometry, parameters calibration of the equipment and the experimental results on HL-2A tokamak. 展开更多
关键词 reflectometry TIME-DELAY density profile
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Experimental study of core and edge fluctuations by reflectometry on EAST tokamak
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作者 Zhen ZHOU Tao ZHANG +10 位作者 Mingfu WU Kaixuan YE Fubin ZHONG Jia HUANG Kangning GENG Yukai LIU Gongshun LI Haoming XIANG Yumin WANG Fei WEN Sanqiu LIU 《Plasma Science and Technology》 SCIE EI CAS CSCD 2021年第7期8-14,共7页
An eight-channel poloidal correlation reflectometer(PCR)with O-mode polarization has been installed in the EAST tokamak to measure the fluctuations from core to edge.The PCR launches eight different frequency microwav... An eight-channel poloidal correlation reflectometer(PCR)with O-mode polarization has been installed in the EAST tokamak to measure the fluctuations from core to edge.The PCR launches eight different frequency microwaves(20.4,24.8,33,40,42.4,48,52.6,57.2 GHz)into the plasma from the low field side and two poloidally separated antennae are used to receive the reflected waves.As a result,the diagnostic can measure fluctuations in eight(radial)×two(poloidal)spatial positions.The diagnostic has been applied to study the core and edge pedestal fluctuations during an inter-ELM phase in H-mode plasma.This inter-ELM phase can be divided into two stages.In the first stage,a low frequency(<50 kHz)broadband fluctuation dominates in the pedestal gradient region.In the second stage,this fluctuation is strongly suppressed and quasi-coherent fluctuations(QCFs)appear.The QCF’s amplitude increases with the pedestal density gradient,implying density gradient driven instabilities.But the core fluctuations inside the pedestal show no evident changes during the inter-ELM phase. 展开更多
关键词 core fluctuation edge fluctuation reflectometry
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Measurement of Density Profile with Step-Swept Microwave Reflectometry
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作者 潘宇东 伊藤智之 《Plasma Science and Technology》 SCIE EI CAS CSCD 2003年第2期1689-1694,共6页
A one-channel microwave reflectometer is used to measure the electron densityprofile in a low-density plasma experiment (n_e < 0.27 x 10^(19) m^(-3)) sustained by 2.45 GHzlower hybrid current drive (LHCD) on TRIAM-... A one-channel microwave reflectometer is used to measure the electron densityprofile in a low-density plasma experiment (n_e < 0.27 x 10^(19) m^(-3)) sustained by 2.45 GHzlower hybrid current drive (LHCD) on TRIAM-1M. In order to remove the effect of phase runawayphenomena, a step-like frequency-sweeping way is used and a special phase analysis technique isintroduced. The density profile is reconstructed in TRIAM-1M with the swept frequency ranged from 6GHz to 15 GHz. The corresponding cutoff density is from (0.045 ~ 0.28) x 10^(19) m^(-3) in theordinary polarization mode. The results are in good agreement with the measurements from amulti-channel 2 mm-wavelength interferometer. 展开更多
关键词 reflectometry phase runaway phenomena electron density profile
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Investigation of nonlinear effects in Doppler reflectometry using full-wave synthetic diagnostics
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作者 O L KRUTKIN A B ALTUKHOV +9 位作者 A D GURCHENKO E Z GUSAKOV S HEURAUX M A IRZAK L A ESIPOV T P KIVINIEMI C LECHTE S LEERINK P NISKALA G ZADVITSKIY 《Plasma Science and Technology》 SCIE EI CAS CSCD 2020年第6期1-7,共7页
In this work,Doppler reflectometry(DR)and radial correlation DR(RCDR)nonlinear scattering effects are studied using full-wave modeling with a set of representative FT-2 tokamak turbulence as inputs.Narrowing of the RC... In this work,Doppler reflectometry(DR)and radial correlation DR(RCDR)nonlinear scattering effects are studied using full-wave modeling with a set of representative FT-2 tokamak turbulence as inputs.Narrowing of the RCDR correlation function and widening of the DR poloidal wavenumber spectrum are demonstrated.An effect on the dependence of the DR signal frequency shift on the probing wavenumber is found,namely,this dependence‘linearizing’in the nonlinear scattering regime.Nonlinear effects are shown to be weaker for O-mode probing than for X-mode probing,while a faster transition to nonlinear regime is demonstrated for RCDR compared to DR in both probing scenarios. 展开更多
关键词 reflectometry numerical modeling full-wave modeling
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Combining Cubic Spline Interpolation and Fast Fourier Transform to Extend Measuring Range of Reflectometry
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作者 Ju Cheng Jian Lu +7 位作者 Hong-Chao Zhang Feng Lei Maryam Sardar Xin-Tian Bian Fen Zuo Zhong-Hua Shen Xiao-Wu Ni Jin Shi 《Chinese Physics Letters》 SCIE CAS CSCD 2018年第5期20-24,共5页
The reflectometry is a common method used to measure the thickness of thin films. Using a conventional method,its measurable range is limited due to the low resolution of the current spectrometer embedded in the refle... The reflectometry is a common method used to measure the thickness of thin films. Using a conventional method,its measurable range is limited due to the low resolution of the current spectrometer embedded in the reflectometer.We present a simple method, using cubic spline interpolation to resample the spectrum with a high resolution,to extend the measurable transparent film thickness. A large measuring range up to 385 m in optical thickness is achieved with the commonly used system. The numerical calculation and experimental results demonstrate that using the FFT method combined with cubic spline interpolation resampling in reflectrometry, a simple,easy-to-operate, economic measuring system can be achieved with high measuring accuracy and replicability. 展开更多
关键词 FIGURE FFT Combining Cubic Spline Interpolation and Fast Fourier Transform to Extend Measuring Range of reflectometry
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Real Time Power Monitoring Detection Based on Sequence Time Domain Reflectometry Approach
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作者 Sam Moayedi Subhaditya Shom +1 位作者 Andrew Harms Mahmoud Alahmad 《Journal of Computer and Communications》 2018年第1期92-103,共12页
Sequence Time Domain Reflectometry (STDR) have been demonstrated to be a powerful technique for detecting the length of cable or length of open circuit or short circuit cables. Using this method along with using smart... Sequence Time Domain Reflectometry (STDR) have been demonstrated to be a powerful technique for detecting the length of cable or length of open circuit or short circuit cables. Using this method along with using smart meter on the main electrical panel board to monitor consumption if load at each circuit, enable user to monitor power consumption at each node (power outlet) only by operating a smart digital meter and an STDR circuitry on each circuit at the main electrical panel board. This paper introduces this method and examines it on dead-wire and energized wire with a load connected across it. Experimental results are demonstrated for both types. Test result show the potential application of this approach to provide consumption information and potential cost saving via feedback for users. 展开更多
关键词 Wire LENGTH DETECTION SEQUENCE TIME DOMAIN reflectometry (STDR) TIME DOMAIN reflectometry (TDR) Maximum LENGTH SEQUENCE Coupling Power Consumption Monitoring
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Snow Water Equivalent Estimation for a Snow-Covered Prairie Grass Field by GPS Interferometric Reflectometry
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作者 Mark D. Jacobson 《Positioning》 2012年第3期31-41,共11页
The amount of water stored in snowpack is the single most important measurement for the management of water supply and flood control systems. The available water content in snow is called the snow water equivalent (SW... The amount of water stored in snowpack is the single most important measurement for the management of water supply and flood control systems. The available water content in snow is called the snow water equivalent (SWE). The product of snow density and depth provides an estimate of SWE. In this paper, snow depth and density are estimated by a nonlinear least squares fitting algorithm. The inputs to this algorithm are global positioning system (GPS) signals and a simple GPS interferometric reflectometry (GPS-IR) model. The elevation angles of interest at the GPS receiving antenna are between 50 and 300. A snow-covered prairie grass field experiment shows potential for inferring snow water equivalent using GPS-IR. For this case study, the average inferred snow depth (17.9 cm) is within the in situ measurement range (17.6 cm ± 1.5 cm). However, the average inferred snow density (0.13 g.cm-3) overestimates the in situ measurements (0.08 g.cm-3 ± 0.02 g.cm-3). Consequently, the average inferred SWE (2.33 g.cm-2) also overestimates the in situ calculations (1.38 g.cm-2 ± 0.36 g.cm-2). 展开更多
关键词 Global Positioning System (GPS) GPS Interferometric reflectometry (GPS-IR) SNOW Depth SNOW Density SNOW Water Equivalent (SWE) Multipath Specular Reflection
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First results of turbulence investigation on Globus-M2 using radial correlation Doppler reflectometry
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作者 A.PONOMARENKO A.YASHIN +8 位作者 V.GUSEV E.KISELEV G.KURSKIEV V.MINAEV Y.PETROV N.SAKHAROV P.SHCHEGOLEV E.TKACHENKO N.ZHILTSOV 《Plasma Science and Technology》 SCIE EI CAS 2024年第10期49-55,共7页
The first results of investigation of the turbulence structure using Doppler backscattering(DBS)on the Globus-M2 tokamak are presented.A one-channel DBS system with a variable probing frequency within the 18–26 GHz r... The first results of investigation of the turbulence structure using Doppler backscattering(DBS)on the Globus-M2 tokamak are presented.A one-channel DBS system with a variable probing frequency within the 18–26 GHz range was installed to investigate the edge plasma at normalized minor radiiρ=0.9–1.1.Radial correlation Doppler reflectometry was used to study the changes in turbulence eddies after the LH transition.Correlation analysis was applied to the phase derivative of complex in-phase and quadrature(IQ)signals of the DBS diagnostic as it contains information about the poloidal plasma rotation velocity.In L-mode,the radial correlation length L_(r)is estimated to be 3 cm and after transition to H-mode reduces to approximately 2 cm.Gyrokinetic modelling in a linear local approximation using code GENE indicates that the instability with positive growth rate at the normalized minor radiusρ=0.75 in L-mode and H-mode on Globus-M2 was the ion temperature gradient(ITG)mode. 展开更多
关键词 tokamak turbulence Doppler backscattering correlation reflectometry
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