Helicon-type radiofrequency plasma thrusters and magnetic plasma nozzles

Takahashi, Kazunori

doi:10.1007/s41614-019-0024-2

Cited by 162 publications

(111 citation statements)

References 218 publications

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“…is exerted on somewhere and somehow, e.g., to the acceleration grids by the electrostatic force in an ion gridded thruster 19 , to the physical axial wall by the sheath-accelerated ions [20][21][22] , and to the magnetic field by the Lorentz force [23][24][25][26][27][28] . Figure 1 shows the schematic diagram of a new type of the electric propulsion device called a magnetic nozzle radiofrequency (rf) plasma thruster 29,30 , which consists of an insulator source tube wound by an rf antenna and a solenoid providing a static magnetic field. Since the magnetic field eventually diverges downstream of the source tube, the magnetic nozzle is inevitably formed there.…”

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Spatially- and vector-resolved momentum flux lost to a wall in a magnetic nozzle rf plasma thruster

Takahashi

Sugawara

Andõ

2020

Sci Rep

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Most of the artificial low-pressure plasmas contact with physical walls in laboratories; the plasma loss at the wall significantly affects the plasma device performance, e.g., an electric propulsion device. Near the surface of the wall, ions are spontaneously accelerated by a sheath and deliver their momentum and energy to the wall, while most of the electrons are reflected there. The momentum flux of the ions is a vector field, i.e., having both the radial and axial components even if the azimuthal components are neglected in a cylindrical system. Here the spatially-and vector-resolved measurement of the momentum flux near the cylindrical source wall of a magnetic nozzle radiofrequency (rf) plasma thruster configuration is successfully demonstrated by using a momentum vector measurement instrument. The results experimentally identify the spatial profile of a non-negligible axial momentum flux to the wall, while the radially accelerated ions seem to be responsible for the energy loss to the wall. The spatial profiles of the radial and axial momentum fluxes and the energy lost to the wall are significantly affected by the magnetic field strength. The results contribute to understand how and where the momentum and energy in the artificial plasma devices are lost, in addition to the presently tested thruster. The plasma momentum is one of the fundamental physical quantities associated with static and dynamic phenomena of plasmas in nature and laboratories. The energy flux being a scalar quantity can be given by the magnitude of the velocity, while the momentum flux is a vector quantity in general. It is crucial to understand and characterize the momentum transport, conversion, gain, and loss mechanisms for clarifying the structural formation of plasmas such as the astrophysical jets 1 , the particle acceleration in auroras at the Earth and Jupiter 2,3 , the coronal mass ejection from the Sun 4 , the interaction between the plasmas and the geomagnetic field 5 , and so on. In these naturally appearing plasmas, the processes involving the momentum and energy transfer occur due to the interaction with electromagnetic fields, collisions, turbulences, and so on, since they cannot see any physical boundaries in space except for the surface of planets. Terrestrial artificial plasmas ubiquitously contact to physical boundaries; forming a sheath maintaining charge balance in plasmas 6. Plasma-wall interactions involving the momentum transfer and loss also significantly affect the plasma behavior in the laboratories, e.g., in ref. 7,8 , in addition to the interactions occurring in the above-mentioned natural plasmas, e.g., interaction with the magnetic fields 9-11. The electric field perpendicular to the physical boundary is spontaneously formed in the sheath and accelerates the ions toward the boundary; resulting in the transfer of the momentum flux perpendicular to the surface. However, if they have velocity components parallel to the boundary surface, they can also deliver their momentum parallel to the boundary. Therefore,...

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Spatially- and vector-resolved momentum flux lost to a wall in a magnetic nozzle rf plasma thruster

Takahashi

Sugawara

Andõ

2020

Sci Rep

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“…in the present experiment. The whole structure of the plasma source can be biased by inserting the bipolar power supply (V bias ) between the discharge chamber and the plasma grid for the control of the plasma potential with respect to the PG, being similar to [20,21]. The positive ion beam can be extracted and accelerated from the plasma source by applying extraction and acceleration voltages V ext and V acc between the EG and PG and between the GG and EG, respectively, where V ext =1.5 kV and V acc =8 kV are chosen in the present experiment.…”

Section: Methodsmentioning

confidence: 99%

Spatiotemporal oscillation of an ion beam extracted from a potential-oscillating plasma source

et al. 2019

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A radiofrequency oscillation is successfully superimposed on a plasma potential of a filamented source plasma in an ion beam source while maintaining a constant plasma density, in order to investigate effects of oscillating source plasma potential on an extracted ion beam. The experiment is preliminarily performed with a positive argon ion beam source. A class-D amplifier operational over a wide range of a frequency from a few tens of kHz to several MHz is installed; leading the oscillation of the plasma potential in the plasma source for the frequency range being tested. The beam current profile downstream of the extraction grids shows an oscillation of the beam current at the peripheral region of the ion beam; implying that the oscillation of a beam halo is induced by the potential oscillation of the source plasma.

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“…Radiofrequency (rf) plasma source operated in the frequency of 1-100 MHz has been widely used for various applications such as industrial plasmas [1,2], space propulsion devices [3,4], and fusion plasmas [5]. To transfer the rf power to a load, the load impedance has to be matched to the output impedance of the generator and the characteristic impedance of a power transmission line, being typically 50 .…”

Section: Introductionmentioning

confidence: 99%

Fast and Automatic Control of a Frequency-Tuned Radiofrequency Plasma Source

2020

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A frequency-tuned radiofrequency (rf) plasma source is automatically controlled to minimize the rf power reflection and to maintain the constant net rf power corresponding to the forward power minus the reflected power. The experiment is performed with a power amplifier operational for the frequency of 37-43 MHz, a compact helicon source consisting of a loop antenna, a solenoid, and an insulator tube. The rf power is supplied to the rf antenna via an impedance matching circuit consisting of only fixed small ceramic capacitors. It is demonstrated that the reflection coefficient of the rf power is minimized within ∼10 ms, and the net power is successfully maintained at a constant level.

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Helicon-type radiofrequency plasma thrusters and magnetic plasma nozzles

Cited by 162 publications

References 218 publications

Spatially- and vector-resolved momentum flux lost to a wall in a magnetic nozzle rf plasma thruster

Spatially- and vector-resolved momentum flux lost to a wall in a magnetic nozzle rf plasma thruster

Spatiotemporal oscillation of an ion beam extracted from a potential-oscillating plasma source

Fast and Automatic Control of a Frequency-Tuned Radiofrequency Plasma Source

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