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Aug 2000

Volume 71, Issue 8, pp. 2959-3233

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back to top ELECTRONICS; ELECTROMAGNETIC TECHNOLOGY; MICROWAVES

A medium-frequency interferometer for studying auroral radio emissions

J. M. Hughes, J. LaBelle, and M. L. Trimpi

Rev. Sci. Instrum. 71, 3200 (2000); http://dx.doi.org/10.1063/1.1305518 (7 pages) | Cited 6 times

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An interferometer for use between 2.5 and 3.0 MHz has recently been developed for the purpose of studying auroral radio emissions. The instrument consists of an array of 17 antennas, associated electronics for amplitude and phase measurements, and computer hardware for instrument control and data recording. In its standard operational mode, the instrument sweeps from 2.5 to 3.0 MHz in 1 kHz steps every 1.5 s. The intensity of the received signal and the phase at each antenna is measured for each 1-kHz-wide bin. These data can be used to produce spectrograms showing the intensity of the received signal versus frequency and time and for determining the direction of arrival for any signal in the instrument bandwidth. © 2000 American Institute of Physics.
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92.60.hw Airglow and aurorae
95.55.Jz Radio telescopes and instrumentation; heterodyne receivers
95.55.Br Astrometric and interferometric instruments

Adjustable resonant cavity for measuring the complex permittivity of dielectric materials

D. Gershon, J. P. Calame, Y. Carmel, and T. M. Antonsen

Rev. Sci. Instrum. 71, 3207 (2000); http://dx.doi.org/10.1063/1.1304865 (3 pages) | Cited 4 times

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An adjustable resonance cavity was developed to measure the complex permittivity of dielectric materials. The cavity has an inner diameter of 16.400 cm and an inner height of 2.54 cm. The aluminum stationary wall holder was positioned about 10.8 cm above the top of the cavity. It was fixed into place by three 1.27-cm-diam linear shafts. By suspending from the wall holder, the movable wall moved vertically by sliding on 1.27 cm bore-closed ball bushings. By turning a 1 in.-12 nut, the movable wall could be positioned so that the cavity height equaled the height of the sample. Therefore, this enables the measurement of the permittivity of samples with heights between 0.88 and 1.91 cm and radius between 1.27 and 3.18 cm. The complex permittivity of the sample was calculated based upon the sample dimensions, central frequency of TMono modes, and Q factor of the resonance curve using an exact solution. The complex permittivity was measured at the three lowest modes, where the frequency span is 1–4 GHz. © 2000 American Institute of Physics.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
84.40.Az Waveguides, transmission lines, striplines
77.22.Ch Permittivity (dielectric function)

Multimegawatt solid state rf driver for generating rotating magnetic fields

J. T. Slough, K. E. Miller, D. E. Lotz, and M. R. Kostora

Rev. Sci. Instrum. 71, 3210 (2000); http://dx.doi.org/10.1063/1.1304873 (4 pages) | Cited 3 times

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A radio frequency (rf) system using solid state switching has been designed and constructed that is capable of driving a pair of loop antenna with a circulating power of 60 MW for millisecond pulses. The primary application of this system is to produce an oscillating magnetic field in the frequency range of 0.2–0.7 MHz, to generate and sustain a large plasma current. The maximum power transfer from the rf source was measured to be greater than 10 MW. The driver consisted of 12 insulated gate bipolar transistor modules driven in parallel, and was capable of switching 20 kA at 1700 V. A sinusoidal current waveform with large circulating currents was obtained on the antenna by incorporating the antenna in a high Q (60), parallel LCR resonant circuit. The low impedance switch driver was matched to the antenna load through a 20:1 step-up air core transformer with a coupling efficiency of 99%. © 2000 American Institute of Physics.
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52.55.Ez Theta pinch
84.30.Jc Power electronics; power supply circuits
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