Control of unsteady laser-produced plasma-flow with a multiple-coil magnetic nozzle

Morita, T.; Edamoto, Masafumi; Miura, Shun; Sunahara, A.; Saito, Noritaka; Itadani, Yutaro; Kojima, Tadao; Mori, Yoshitaka; Johzaki, Tomoyuki; Kajimura, Yoshihiro; Fujioka, Shinsuke; Yogo, Akifumi; Nishimura, Hiroaki; Nakashima, Hideharu; Yamamoto, Naoji

doi:10.1038/s41598-017-09273-3

Cited by 13 publications

(11 citation statements)

References 19 publications

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“…A plasma medium supports a large number of electromagnetic waves [1,2]. Understanding the characteristics of these waves is essential for enriching our knowledge of plasma physics [3] and for developing plasma based applications [4]. One of the primary diagnostics used by plasma physicists to measure a time varying wave magnetic fields is a B-dot probe [5,6].…”

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confidence: 99%

Understanding the working of a B-dot probe

et al. 2018

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Magnetic pickup loops or B-dot probes are one of the oldest known sensors of time varying magnetic fields. The operating principle is based on Faraday's law of electromagnetic induction. However, obtaining accurate measurements of time-varying magnetic fields using these kinds of probes is a challenging task. A B-dot probe and its associated circuit are prone to electrical oscillations. As a result, the measured signal may not faithfully represent the magnetic field sampled by the B-dot probe. In this paper, we have studied the transient response of a B-dot probe and its associated circuit to a time varying magnetic field. Methods of removing the oscillations pertaining to the detector structure are described. After removing the source of the oscillatory signal, we have shown that the time integrated induced emf measured by the digitizer is linearly proportional to the magnetic field sampled by the B-dot probe, thus verifying the faithfulness of the measured signal.

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Understanding the working of a B-dot probe

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“…by Lorentz force. This system is called a magnetic thrust chamber [5,6,7,8,9]. The magnetic thrust chamber expels the plasma as an unsteady flow.…”

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Analysis of plasma detachment in the magnetic thrust chamber using full particle-in-cell simulation

Kojima

Morita

Yamamoto

2020

High Energy Density Physics

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A magnetic nozzle, which is a convergent-divergent magnetic field to control a plasma flow, has been investigated for application to plasma propulsion systems in spaceships. In the magnetic nozzle, plasma thermal energy is converted to one-directional kinetic energy by Lorentz force to generate thrust. Although magnetic field structure and strength are optimized for improvement of the thrust performance, it is essential to understand physical processes of plasma ejection from the nozzle, because the plasma may flow back along lines of magnetic field if the directed plasma continues being strongly magnetized. It is assumed, for one of the scenarios to explain a plasma detachment, that a plasma detaches from magnetic field when a cyclotron radius exceeds a scale length of magnetic field in size. Hence, we investigate a plasma detachment condition by analyzing parameters of the plasma for unmagnetization. We assumed individual particle motion of a fully ionized plasma in the magnetic nozzle and conducted a full particle-in-cell simulation in a two-dimensional coordinate system. We calculated a ratio of cyclotron radius to a scale length of the magnetic field. The ratio increased in a downstream due to variation of magnetic field induced from a diamagnetic cavity, suggesting unmagnetization.

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“…Magnetic nozzles for advanced rocket systems (laser fusion rockets) require magnetic fields of several tesla sustained for several milliseconds in a meter-scale region for flight models 4 and fields of several tesla for tens of microseconds in a centimeter-scale region for scaled-down experimental models. 5,6 In previous research, kilotesla magnetic fields were generated using a capacitor-coil target and a high-power laser beam. 7 This method is able to produce a sharp pulse of quite high magnetic field in a small volume, but the pulse width is only a few nanoseconds.…”

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confidence: 99%

Portable and noise-tolerant magnetic field generation system

Edamoto

Morita

Saito

et al. 2018

Review of Scientific Instruments

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We have successfully developed a portable pulsed magnetic field generation system incorporating a number of techniques to avoid the effects of noise, including shielding, a self-power capability, and a high-capability semiconductor switch. The system fits into a cubical box less than 0.5 m in linear dimensions and can easily be installed in experimental facilities, including noisy environments such as high-power laser facilities. The system can generate a magnetic field of several tesla sustainable for several tens of microseconds over a spatial scale of several centimeters. In a high-power laser experiment with Gekko-XII, the system operated stably despite being subjected to a high level of electrical noise from laser shots of 600 J.

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Control of unsteady laser-produced plasma-flow with a multiple-coil magnetic nozzle

Cited by 13 publications

References 19 publications

Understanding the working of a B-dot probe

Understanding the working of a B-dot probe

Analysis of plasma detachment in the magnetic thrust chamber using full particle-in-cell simulation

Portable and noise-tolerant magnetic field generation system

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