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论文类型：期刊论文

发表时间：2010-05-01

发表刊物：REVIEW OF SCIENTIFIC INSTRUMENTS

收录刊物：SCIE、EI、PubMed

卷号：81

期号：5

页面范围：054703

ISSN号：0034-6748

关键字：plasma probes; transformer windings; transformers

摘要：A tunable center-tapped transformer is proposed to increase the output of a rf magnetic probe and improve the signal-to-noise ratio. The tuning is implemented by a variable capacitor connected parallel with the primary winding of the tunable center-tapped transformer. Undesirable common-to-differential conversion is reduced by installing a compensating capacitor. In addition, a planar Faraday shield is installed between the windings of the transformer to further suppress the electrostatic coupling. It is found that tuning the variable capacitor can result in a resonance in the output voltage of the rf magnetic probe. The largest output voltage, achieved with the tunable magnetic probe under the optimal condition, is higher than that with a conventional one by an order of magnitude. Effects of the compensating capacitance on the common-mode output voltage are studied and discussed. Influences of parameters such as cable length, the coupling coefficient, and the step-up ratio of the transformer on the output voltage are also presented. Analytical derivations and numerical calculations based on the equivalent circuit are performed to elucidate the characteristics of the differential mode. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3402288]