Kazuki Yano

Bio: Kazuki Yano is an academic researcher from Tokyo University of Agriculture and Technology. The author has contributed to research in topics: Helicon & Plasma. The author has an hindex of 4, co-authored 4 publications receiving 38 citations.

Thrust Characteristics of High-Density Helicon Plasma Using Argon and Xenon Gases

Abstract: A helicon plasma thruster has been studied to develop a completely electrodeless electric thruster using high-density helicon plasmas. The proposed helicon plasma thruster involves two processes: the generation of source dense plasma by using a helicon wave, and the additional acceleration of the generated plasma by using the Lorentz force generated by the product of the induced azimuthal current and external radial magnetic field. This additional acceleration method requires additional electrodes or coils, leading to a longer discharge tube. Therefore, it is necessary to find a good configuration that minimizes wall losses within the discharge tube. Here, thrust characteristics such as thrust, thrust-to-power ratio, specific impulse, and thrust efficiencies of argon and xenon gases were studied, using a radio frequency of 7 MHz and an input power less than 3 kW, to optimize the target plasma without employing an additional acceleration method. A helicon plasma source, with electromagnets and permanent ma...

Suppression of diamagnetism by neutrals pressure in partially ionized, high-beta plasma

Abstract: Suppression of diamagnetism in a partially ionized plasma with high beta was experimentally investigated by the use of Langmuir and Hall sensor probes, focusing on a neutrals pressure effect. The plasma beta, which is the ratio of plasma to vacuum magnetic pressures, varied from ∼1% to >100% while the magnetic field varied from ∼120 G to ∼1 G. Here, a uniform magnetized argon plasma was operated mostly in an inductive mode, using a helicon plasma source of the Large Helicon Plasma Device [S. Shinohara et al., Phys. Plasmas 16, 057104 (2009)] with a diameter of 738 mm and an axial length of 4860 mm. Electron density varied from 5 × 1015 m−3 to <3 × 1018 m−3, while an argon fill pressure was varied from ∼0.02 Pa to 0.75 Pa as well as the magnetic field mentioned above, with the fixed radio frequency (rf) and power of 7 MHz and ∼3.5 kW, respectively. The observed magnetic field reduction rate, a decrease of the magnetic field divided by the vacuum one, was up to 18%. However, in a certain parameter regime, w...

Spatial measurement in rotating magnetic field plasma acceleration method by using two-dimensional scanning instrument and thrust stand.

Abstract: A two-dimensional scanning probe instrument has been developed to survey spatial plasma characteristics in our electrodeless plasma acceleration schemes. In particular, diagnostics of plasma parameters, e.g., plasma density, temperature, velocity, and excited magnetic field, are essential for elucidating physical phenomena since we have been concentrating on next generation plasma propulsion methods, e.g., Rotating Magnetic Field plasma acceleration method, by characterizing the plasma performance. Moreover, in order to estimate the thrust performance in our experimental scheme, we have also mounted a thrust stand, which has a target type, on this movable instrument, and scanned the axial profile of the thrust performance in the presence of the external magnetic field generated by using permanent magnets, so as to investigate the plasma captured in a stand area, considering the divergent field lines in the downstream region of a generation antenna. In this paper, we will introduce the novel measurement instrument and describe how to measure these parameters.

High-Density Helicon Plasma Thrusters Using Electrodeless Acceleration Schemes

Abstract: We have been studying long-lifetime helicon plasma thrusters as the Helicon Electrodeless Advanced Thruster (HEAT) project. Two important elements of the proposed helicon plasma thruster are a generation of a dense source plasma using a helicon wave, and an acceleration of the plasma by the Lorentz force using the product of the induced azimuthal current and static radial magnetic field. Here, in order to eliminate damage of electrodes, both generation and acceleration schemes are operated in non-contact condition between the plasma and electrodes. Acceleration schemes use two type of coils: rotating magnetic field coils and azimuthal mode number m = 0 ones. These studies have been carried out on the Large Mirror Device (LMD), which has two types the magnetic field source, permanent magnets and electromagnets, and the Small Helicon Device (SHD), which has small diameter discharge tubes. In this paper, current performances of acceleration schemes are reported.

Helicon-type radiofrequency plasma thrusters and magnetic plasma nozzles

Abstract: Development of electrodeless radiofrequency plasma thrusters, e.g., a helicon thruster, has been one the of challenging topics for future high-power and long-lived electric propulsion systems. The concept simply has a radiofrequency plasma production/heating source and a magnetic nozzle, while it seems to include many aspects of physics and engineering issues. The plasma produced inside the source is transported along the magnetic field lines and expands in the magnetic nozzle, where the plasma is spontaneously accelerated into the axial direction along the magnetic nozzle, yielding a generation of the thrust force. Hence, the plasma transport and spontaneous acceleration phenomena in the magnetic nozzle are key issues to improve the performance of the thrusters. Since the thrust is equal in magnitude and opposite in direction to momentum flux exhausted from the system, the direct measurement of the thrust can reveal not only the thruster performance but also fundamental physical quantity of plasma momentum flux. Here studies on fundamental physics relating to the thruster development and the technology for the compact and efficient system are reviewed; the current status of the thruster performance is shown. Finally, a recently proposed future new application of the thruster is also discussed.

Perspectives, frontiers, and new horizons for plasma-based space electric propulsion

Abstract: There are a number of pressing problems mankind is facing today that could, at least in part, be resolved by space systems. These include capabilities for fast and far-reaching telecommunication, surveying of resources and climate, and sustaining global information networks, to name but a few. Not surprisingly, increasing efforts are now devoted to building a strong near-Earth satellite infrastructure, with plans to extend the sphere of active life to orbital space and, later, to the Moon and Mars if not further. The realization of these aspirations demands novel and more efficient means of propulsion. At present, it is not only the heavy launch systems that are fully reliant on thermodynamic principles for propulsion. Satellites and spacecraft still widely use gas-based thrusters or chemical engines as their primary means of propulsion. Nonetheless, similar to other transportation systems where the use of electrical platforms has expanded rapidly, space propulsion technologies are also experiencing a shift toward electric thrusters that do not feature the many limitations intrinsic to the thermodynamic systems. Most importantly, electric and plasma thrusters have a theoretical capacity to deliver virtually any impulse, the latter being ultimately limited by the speed of light. Rapid progress in the field driven by consolidated efforts from industry and academia has brought all-electric space systems closer to reality, yet there are still obstacles that need addressing before we can take full advantage of this promising family of propulsion technologies. In this paper, we briefly outline the most recent successes in the development of plasma-based space propulsion systems and present our view of future trends, opportunities, and challenges in this rapidly growing field.

Helicon high-density plasma sources: physics and applications

Abstract: Helicon high-density (up to ~1013 cm−3) plasma sources using a radio frequency wave in the presence of a magnetic field under a low pressure are very promising for various application fields owing ...

High temperature electrons exhausted from rf plasma sources along a magnetic nozzle

Abstract: Two dimensional profiles of electron temperature are measured inside and downstream of a radiofrequency plasma thruster source having a magnetic nozzle and being immersed in vacuum. The temperature is estimated from the slope of the fully swept I-V characteristics of a Langmuir probe acquired at each spatial position and with the assumption of a Maxwellian distribution. The results show that the peripheral high temperature electrons in the magnetic nozzle originate from the upstream antenna location and are transported along the “connecting” magnetic field lines. Two-dimensional measurements of electron energy probability functions are also carried out in a second simplified laboratory device consisting of the source contiguously connected to the diffusion chamber: again the high temperature electrons are detected along the magnetic field lines intersecting the wall at the antenna location, even when the antenna location is shifted along the main axis. These results demonstrate that the peripheral energet...