Multichannel microwave interferometer with an antenna switching system for electron density measurement in a laboratory plasma experiment

Kawamori, Eiichirou; Lin, Yan‐Hui; Mase, A.; Nishida, Yasushi; Cheng, C. Z.

doi:10.1063/1.4865117

Cited by 4 publications

(3 citation statements)

References 8 publications

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“…Among the common products, an electrical switch using PIN diode is beneficial in terms of quick time response. The application of PIN diode switch to microwave interferometer was performed in the past [1,2].…”

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confidence: 99%

Measurement of ICRF wave propagation using a microwave reflectometer with fast antenna switching on GAMMA 10

et al. 2017

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Slow Alfvén wave in ion cyclotron range of frequency (ICRF) is a powerful tool to heat ions confined in a mirror field. In spite of its efficient heating effect that has been attained in the central cell of GAMMA 10, there are still unknown characteristics concerning boundary condition, transient variation of heating effect, exact picture of cyclotron damping, and so on. To study these characteristics in detail, a multi-point measurement of the waves inside the hot plasma has been recently developed by using a microwave reflectometer. In addition to a radial profile measurement that is available by a usual reflectometer, an axial measurement has been achieved by arraying transmitting and receiving horn antennas in the axial direction, which are repeatedly switched in time during a discharge with PIN diode switches. Another transmitting and receiving horn antenna pair was newly added to the system and probing at five cross sections was achieved in a single discharge with time resolution of about 1 ms at each antenna pair position. With the upgraded reflectometer system, axial and radial distributions of wave-induced fluctuations and those temporal behavior were clearly observed, offering valuable data on wave physics in a hot mirror plasma.

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confidence: 99%

Measurement of ICRF wave propagation using a microwave reflectometer with fast antenna switching on GAMMA 10

et al. 2017

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“…In addition to RIDFPs, we employed a few sets of Langmuir probes (LPs) for different purposes. An LP measured the plasma density in addition to a microwave interferometer 37 .…”

Section: Methodsmentioning

confidence: 99%

Evidence of entropy cascade in collisionless magnetized plasma turbulence

Kawamori

Lin

2022

Commun Phys

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The turbulence of collisionless magnetized plasmas, as observed in space, astrophysical, and magnetically confined fusion plasmas, has attracted considerable interest for a long-time. The entropy cascade in collisionless magnetized plasmas is a theoretically proposed dynamics comparable to the Kolmogorov energy cascade in fluid turbulence. Here, we present evidence of an entropy cascade in laboratory plasmas by direct visualization of the entropy distribution in the phase space of turbulence in laboratory experiments. This measurement confirms the scaling laws predicted by the gyrokinetic theory with the dual self-similarity hypothesis, which reflects the interplay between the position and velocity of ions by perpendicular nonlinear phase mixing. This verification contributes to our understanding of turbulent heating in the solar corona, accretion disks, and magnetically confined fusion plasmas.

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“…The PIN diode switch itself has been used in plasma diagnostics in the past and helped to reduce the number of microwave components required to form a multichannel interferometer. 21,22 Here, PIN diode switches are used to form a multi-channel reflectometer for the first time. For the measurement of the temporal behavior of high-frequency fluctuations of the order of MHz (as per this study) or more, the most expensive instrument would be a high-performance digitizer with much wider bandwidths than the measurement frequency and a large memory capacity.…”

Section: Introductionmentioning

confidence: 99%

Multi-point measurement using two-channel reflectometer with antenna switching for study of high-frequency fluctuations in GAMMA 10

Ikezoe

Ichimura

Okada

et al. 2017

Review of Scientific Instruments

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A two-channel microwave reflectometer system with fast microwave antenna switching capability was developed and applied to the GAMMA 10 tandem mirror device to study high-frequency small-amplitude fluctuations in a hot mirror plasma. The fast switching of the antennas is controlled using PIN diode switches, which offers the significant advantage of reducing the number of high-cost microwave components and digitizers with high bandwidths and large memory that are required to measure the spatiotemporal behavior of the high-frequency fluctuations. The use of two channels rather than one adds the important function of a simultaneous two-point measurement in either the radial direction or the direction of the antenna array to measure the phase profile of the fluctuations along with the normal amplitude profile. The density fluctuations measured using this system clearly showed the high-frequency coherent fluctuations that are associated with Alfvén-ion-cyclotron (AIC) waves in GAMMA 10. A correlation analysis applied to simultaneously measured density fluctuations showed that the phase component that was included in a reflected microwave provided both high coherence and a clear phase difference for the AIC waves, while the amplitude component showed neither significant coherence nor clear phase difference. The axial phase differences of the AIC waves measured inside the hot plasma confirmed the formation of a standing wave structure. The axial variation of the radial profiles was evaluated and a clear difference was found among the AIC waves for the first time, which would be a key to clarify the unknown boundary conditions of the AIC waves.

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Multichannel microwave interferometer with an antenna switching system for electron density measurement in a laboratory plasma experiment

Cited by 4 publications

References 8 publications

Measurement of ICRF wave propagation using a microwave reflectometer with fast antenna switching on GAMMA 10

Measurement of ICRF wave propagation using a microwave reflectometer with fast antenna switching on GAMMA 10

Evidence of entropy cascade in collisionless magnetized plasma turbulence

Multi-point measurement using two-channel reflectometer with antenna switching for study of high-frequency fluctuations in GAMMA 10

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