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KT—5C托卡马克离子伯恩斯坦波功率发射系统 总被引:1,自引:1,他引:0
本文概述了在KT-5C托卡马克上研究非线性离子伯恩斯坦波用的新型射频波功率发射系统,给出了工作频率选择和稳定、射频功率的传输调节、脉冲响应、耦合网络及其阻抗变换、移动式天线等实验结果,还给出了测量天线真空负载阻抗的一种简便方法,讨论了有关结果。 相似文献
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基于射频识别技术原理及Friis传输方程, 导出了无源超高频射频识别系统链路模型, 结合二端口网络分析方法, 导出了标签密集环境下的标签天线互阻抗计算表达式.利用单阅读器单标签时的标签阻抗匹配条件, 基于功率传输系数及调制因子, 分析了互偶效应对系统链路的影响.在开阔室内环境中, 测试了双标签及标签单、双平面布置情形下的阅读器天线最小发射功率及系统识别率.测试结果表明, 双标签及双平面情形下, 阅读器天线最小发射功率变化率分别为(-7%, 11.6%)及(-10%, 12.5%).
关键词:
射频识别
密集环境
互偶效应
互阻抗 相似文献
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针对KT-5C托卡马克装置等离子体的射频离子回旋波加热实验,本文给出一种回路天线负载阻抗的简便测量方法和测量结果。该方法的特点是,只涉及射频电流相对比值的测量,不要求专用设备,因此使物理量的标定、数据记录和处理都变得简单易行。 相似文献
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沈学民 《核聚变与等离子体物理》1996,16(1):20-23
本文提出了在大功率射频发射系统中对一个未知的天线负载,可用二次实验数据来确定双T调配器的参数,以达到射频源和天线负载间的匹配。文中详细地讨论了这种高配法的理论并给出了用以实验的解析公式。 相似文献
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介绍了一种用于大科学工程装置中国散裂中子源(CSNS) 功率升级的RF负氢离子源大功率射频功率耦合系统的研制。主要内容包括射频功率耦合系统的构造, 指标计算分配以及具体实现, 重点阐述了射频功率放大器、隔离变压器、阻抗变压调谐器以及配套的电源、控制和冷却系统的设计, 并对整个系统的结构和热设计提出了工程解决方法。针对离子源功率耦合系统的特点作了细致的分析, 并以此为基础, 研制出了一款输出功率达80kW的射频功率耦合系统产品。 相似文献
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为满足中国散裂中子源打靶功率提升需求,加速器采用外置天线射频负氢离子源替换此前使用的潘宁表面负氢离子源,为加速器提供高品质和高稳定的束流。文章主要介绍了基于EPICS软件系统和PLC硬件平台的射频负氢离子源控制系统设计方案和具体实现。针对射频功率源的电磁干扰和高压平台打火造成设备损坏,给出了相应的解决措施。此外,为提高离子源长期运行稳定性,设计了放电室高精度注铯控制程序及打靶功率稳定程序。控制系统自投入运行以来,运行稳定可靠,为离子源的高效运行提供了有力保障。 相似文献
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开展了波长为532 nm、脉宽为8 ns的纳秒激光诱导空气等离子体射频电磁辐射特性实验研究,基于锥形天线探测空气等离子体在30-800 MHz频谱范围有较强的射频电磁辐射,是等离子体内电偶极子振荡变速运动造成的.实验结果表明:随激光能量增加,30-200 MHz范围内射频辐射强度逐渐变强,但360-600 MHz频率范围射频辐射强度逐渐变弱.等离子体射频辐射的空间分布依赖于入射激光的偏振方向,当激光偏振方向与天线放置方向一致时,该方向上空气等离子体的射频辐射强度高,谱线较丰富.射频辐射总功率随激光能量先增加后降低,采用等离子体电子密度变化对等离子体频率及等离子体衰减系数影响(制约)关系,对射频辐射总功率随激光能量的变化规律进行了解释. 相似文献
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Double electron muon resonance was studied with comparable amplitudes of the static and rf magnetic fields. The experiments were carried out in fused quartz and employed a resonant linearly-polarized rf field and a small static field. For small amplitudes of the rf field a three-line frequency spectrum was obtained consisting of a central line at the rf frequency and two weaker lines of equal amplitude symmetrically positioned about the central line. A symmetrical three line spectrum is predicted for muonium using the rotating wave approximation (RWA). For large rf fields the amplitudes of the three lines were not symmetric and depended on whether positrons were observed parallel or perpendicular to the beam. For very large rf fields the total amplitude of all the lines was less than for lower rf fields. These results do not agree with the theory using the RWA and no satisfactory theory currently exists. 相似文献
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Observation of harmonic and subharmonic Shapiro steps in orthorhombic TaS3 in the presence of combined rf and dc drive is reported, demonstrating that both the harmonic and subharmonic steps are a general characteristic of charge-density-wave response. Compared to NbSe3, the noise spectrum is typically much broader in TaS3, leading to poorly defined steps at small rf voltages. The steps sharpen with larger amplitudes of rf. Increased rf amplitude is also accompanied by an increase in the CDW current density at a given step, but this increase approaches a limiting value for large rf levels. The results are interpreted as evidence for increased coherence of the CDW response in the presence of large rf driving fields. 相似文献
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Michal Kopcewicz 《Hyperfine Interactions》1992,71(1-4):1453-1456
A systematic study of the dependence of the radio frequency (rf) collapse effect on the frequency of the rf field which induces
the fast relaxation of the hyperfine field was performed for Permalloy and amorphous Fe45Ni30Si10B15 alloy. The rf collapse was studied for the frequency range of 12 MHz to 64 MHz. The results show that the rf collapse appears
gradually in both materials as the rf field frequency exceeds the Larmor frequency what is in agreement with the model predictions. 相似文献
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A new sensor principle for detection of patient movement in magnetic resonance imaging has been successfully applied for the reduction of motion artifacts. It uses a device that is already present in every MRI system, namely the rf coil. Patient movement within the coil causes changes in the rf impedance match of the coil, which can be measured as variations in the reflected rf power. The principle used for the detection of respiratory and cardiac motion is described, and experimental results measured with several coil arrangements are given. Images are presented which were acquired with respiratory gating derived from the rf body coil of a 2 Tesla whole body MRI system. 相似文献
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We present experimental results for what is to our knowledge the first spectral-hole-burning based rf spectrum analyzer to cover 10 GHz of rf analysis bandwidth. The rf signal of interest is modulated onto an optical carrier, and the resultant optical sidebands are burned into the inhomogeneously broadened absorption band of a Tm3+:YAG crystal. At the same time a second, frequency-swept laser reads out the absorption profile, which is a double-sideband replica of the rf spectrum, and thus the rf spectrum can be deduced after spectral calibration of the nonlinear readout chirp. This initial demonstration shows spectral analysis covering 10 GHz of bandwidth with >5500 spectral channels and provides 43 dB of dynamic range. 相似文献
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The Collapse effect of amorphous alloys Fe38Ni38Mo4B20 and Fe48Ni31Si10B11 in the rf field was investigated by means of the
measurement of the temperature of the samples in rf field and the observations of aftereffect of the strong rf field. The
collapse observed is caused by rf induced magnetic fluctuation rather than thermal effects. The results agree well with the
model based on a magnetic cluster picture. 相似文献
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采用PIC-MC自洽模型,模拟了氮气电容性耦合射频放电的微观等离子体过程及带电粒子(e,N2+,N+)的行为。结果表明,离子(N2+,N+)的运动状态滞后瞬时射频电场的变化;在两极附近,N2+具较高密度,但能量较低,N+具较低的密度但能量较高,两者的密度差6倍左右。两种离子轰击射频电极的能量分布变化规律类似,随放电参数变化,离子(N2+,N+)能量变化显著,其密度变化不明显。模拟的电子能量几率分布与测量结果一致。 相似文献
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《Magnetic resonance imaging》1998,16(8):907-916
The purpose of this study was to investigate how flow affects slice-selective excitation, particularly for radiofrequency (rf) pulses optimized for slice-selective excitation of stationary material. Simulation methods were used to calculate the slice profiles for material flowing at different velocities, using optimal flow compensation when appropriate. Four rf pulses of very different shapes were used in the simulation study: a 90° linear-phase Shinnar-LeRoux pulse; a 90° self-refocusing pulse; a minimum-phase Shinnar-LeRoux inversion pulse; and a SPINCALC inversion pulse. Slice profiles from simulations with a laminar flow model were compared with experimental studies for two different rf pulses using a clinical magnetic resonance imaging (MRI) system. We found that, for a given rf pulse, the effect of flow on slice-selective excitation depends on the product of the selection gradient amplitude, the component of velocity in the slice selection direction, and the square of the rf pulse duration. The shapes of the slice profiles from the Shinnar-LeRoux pulses were relatively insensitive to velocity. However, the slice profiles from the self-refocusing pulse and the SPINCALC pulse were significantly degraded by velocity. Experimental slice profiles showed excellent agreement with simulation. In conclusion, our study demonstrates that slice-selective excitation can be significantly degraded by flow depending on the velocity, the gradient amplitude, and characteristics of the rf excitation pulse used. The results can aid in the design of rf pulses for slice-selective excitation of flowing material. 相似文献
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The beijing electron Positron collider upgrade Project (bePcⅡ) requires its injector linac to upgrade the beam energy and current. thus the accelerating structures in the positron production region must be newly designed and constructed to meet the high gradient demand. these new structures must be tested and conditioned with the high rf power before their installation into the linac tunnel. this paper describes the design and construction of the high power rf test stand, the tuning of the rf power source, the progress and the final results of the rf test and conditioning. 相似文献