Development of a momentum vector measurement instrument in steady-state plasmas

Takahashi, Kazunori; Sugawara, Takeharu; Akahoshi, Hikaru; Takao, Yoshinori; Andõ, Akira

doi:10.1063/1.5050553

Cited by 8 publications

(7 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the present experiment, the relations between the forces (F r , F z ) to the detector and the displacement signals (V r , V z ) can be given as where (F r , F z ) and (V r , V z ) are in units of mN and V, respectively. It is noted that the errors in these calibration coefficients are about 3 -4% as reported before [22]. Thin lines in Fig.…”

Section: Simultaneous Measurements Of Local Axial and Radial Momentumsupporting

confidence: 71%

“…The simultaneous measurements of the axial and radial momentum fluxes to the detector plate are performed by a momentum vector measurement instrument (MVMI) shown in the previous bench test [22] and the schematic is shown in Fig. 1.…”

Section: Simultaneous Measurements Of Local Axial and Radial Momentummentioning

confidence: 99%

“…This procedure can be done in vacuum in the present configuration by connecting all the electric signals and the coil current Fig. 1 Schematic diagram of the momentum vector measurement instrument (MVMI), where the whole structure is flipped from the previous bench test [22]. via vacuum feedthroughs.…”

Section: Simultaneous Measurements Of Local Axial and Radial Momentummentioning

confidence: 99%

See 2 more Smart Citations

Simultaneous Measurements of Local Axial and Radial Momentum Fluxes near a Radial Wall of a Helicon Source

Sugawara

Takahashi

Andõ

2019

Plasma and Fusion Research

Self Cite

View full text Add to dashboard Cite

Axial and radial momentum fluxes near a lateral wall in a helicon plasma source are preliminarily investigated by installing a momentum vector measurement instrument, which has a detector plate mounted on a double-pendulum structure movable in both the axial and radial directions. The result demonstrates the presence of the axial momentum flux transferred to the radial wall, which seems to be delivered by the ions having the axial velocity and lost to the wall. Furthermore, a significantly greater radial momentum flux is lost to the radial wall, implying that the energy loss occurs at the radial wall. The presently shown technique would be useful for identifying the spatial profile of the momentum vector of the plasma.The momentum flux of plasmas is one of the crucial physical quantities associated with acceleration, transport, and confinement of various plasmas [1][2][3][4], since many of the plasma characteristics are well described by momentum equations, which imply that the external forces applied to fluids are balanced to their momentum flux. Therefore, the momentum balance is very often used to model various plasmas ranging from naturally occurring plasmas to artificially-made terrestrial plasmas in small laboratories.One of the direct applications of the plasma momentum flux is an electric propulsion for spacecrafts [5]. The performance of the propulsion devices can be typically characterized by a thrust-to-power ratio F/P, a specific impulse I sp , and a thruster efficiency η p , where F and P are the thrust and the electric power, respectively [6]. The latter two are defined aswhere m dot and g are the mass flow rate of the propellant and the gravitational acceleration at sea level, respectively. Since all of the assessment parameters are given by the thrust F and the well-controlled parameters such as the electric power P and the mass flow rate m dot , the measurement of the thrust F should be taken on top priority to assess the thruster performance in laboratories. According to a momentum conservation of the spacecraft and the exhausted propellant, the thrust force is equal in magnitude and opposite in direction to the momentum flux exhausted from the spacecraft as well known as a rocket equation [6]. Therefore, the direct measurement of the thrust is indeed equivalent to the identification of the absolute value of the total momentum flux of the plasma; being also useful for understanding other plasmas if the local momentum flux can be identified.The direct and individual measurements of the total thrust and thrust components exerted to the axial wall, the radial wall, and the magnetic nozzle have clarified many aspects of physics in a magnetic nozzle helicon plasma thruster [7][8][9][10][11][12][13][14][15]. In highly ionized conditions, e.g., for propellants of xenon and krypton, or for several kW rf power in argon, the axially negative force on the radial wall, which directs to the downstream side and is integrated over the whole inner surface, has been detected in the individual measurement of the ...

show abstract

Section: Simultaneous Measurements Of Local Axial and Radial Momentumsupporting

confidence: 71%

Section: Simultaneous Measurements Of Local Axial and Radial Momentummentioning

confidence: 99%

Section: Simultaneous Measurements Of Local Axial and Radial Momentummentioning

confidence: 99%

See 1 more Smart Citation

Simultaneous Measurements of Local Axial and Radial Momentum Fluxes near a Radial Wall of a Helicon Source

Sugawara

Takahashi

Andõ

2019

Plasma and Fusion Research

Self Cite

View full text Add to dashboard Cite

show abstract

“…Momentum vector measurement instruments. Figure 7 shows the detailed structure of the momentum vector measurement instrument (MVMI), which is very similar to the previous bench test 34 and the preliminarily test in plasmas 50 . The whole structure of the MVMI is flipped from the previous configuration to stabilize the equilibrium position of the axial pendulum when moving the whole structure by the motor stage.…”

Section: Methodsmentioning

confidence: 82%

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

Takahashi

Sugawara

Andõ

2020

Sci Rep

Self Cite

View full text Add to dashboard Cite

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,...

show abstract

“…The IEDF can be obtained from the first derivative of the current-voltage characteristic of the collector electrode in the RFEA. Furthermore, the MVMI, which has been described previously [32][33][34] and shown in figure 3, is mounted on the stage to measure the two-dimensional profile of the horizontal Reprinted from [28], with the permission of AIP Publishing. momentum flux.…”

Section: Methodsmentioning

confidence: 99%

Deflections of dynamic momentum flux and electron diamagnetic thrust in a magnetically steered rf plasma thruster

Imai¹,

Takahashi²

2021

J. Phys. D: Appl. Phys.

Self Cite

View full text Add to dashboard Cite

Two-dimensional characterization of the plasma plume is experimentally performed downstream of a magnetically steered radiofrequency plasma thruster, where the ion beam current, the ion saturation current, and the horizontal dynamic momentum flux, are measured by using the retarding field energy analyzer, the Langmuir probe, and the momentum vector measurement instrument, respectively, in addition to the previously measured horizontal thrust. The measurements show the deflections of the dynamic momentum flux including both the ions and the neutrals; the change in the direction of the dynamic momentum flux is consistent with the previously measured horizontal thrust. Furthermore, the ion saturation current profile implies that the deflected electron-diamagnetic-induced Lorentz force exerted to the magnetic nozzle contributes to the change in the thrust vector. Therefore, it is demonstrated that the deflections of both the dynamic momentum flux and the electron-diamagnetic-induced Lorentz force play an important role in the thrust vector control by the magnetic steering.

show abstract

Development of a momentum vector measurement instrument in steady-state plasmas

Cited by 8 publications

References 38 publications

Simultaneous Measurements of Local Axial and Radial Momentum Fluxes near a Radial Wall of a Helicon Source

Simultaneous Measurements of Local Axial and Radial Momentum Fluxes near a Radial Wall of a Helicon Source

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

Deflections of dynamic momentum flux and electron diamagnetic thrust in a magnetically steered rf plasma thruster

Contact Info

Product

Resources

About