Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/0963-0252/19/4/045009

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2514/1.44784

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1364/OE.17.016933

Other Link： http://www.opticsinfobase.org/abstract.cfm?uri=oe-17-19-16933

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.2822456

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2514/1.18833

Repository Public URL： http://hdl.handle.net/2324/5853

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2514/1.12759

Repository Public URL： http://hdl.handle.net/2324/4209

Language：Japanese   Publishing type：Research paper (scientific journal)  

Operating Characteristics of an Anode Layer Type Hall Thruster

Repository Public URL： http://hdl.handle.net/2324/16994

Language：English   Publishing type：Research paper (scientific journal)  

DOI： doi:10.1585/pfr.18.1404080

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.57350/jesa.3

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.57350/jesa.4

Language：Others   Publishing type：Research paper (scientific journal)  

Abstract

Temporal evolutions of electron temperature (T_e) and electron density (n_e) of photoionized hydrogen plasmas, which were induced by radiation from laser-produced Sn-plasma EUV sources, were measured using the Laser Thomson Scattering (LTS) technique. Measured T_e and n_e ranged from 0.5–2.5 eV and 10¹⁶–10¹⁸ m^-3, respectively, for hydrogen pressures of 50–400 Pa. The T_e of this EUV-induced hydrogen plasma decayed with the thermal relaxation time between electrons and gases. The maximum value of T_e in the time variation depended on hydrogen pressure. The lower the pressure, the higher the maximum T_e, and it reached approximately 2 eV at 50 Pa. The sheath potential between the EUV-induced hydrogen plasma and the unbiased wall might be exceeded 6 eV at 50 Pa, which is sufficient to enhance the removal of Sn-debris from a Mo/Si multilayer mirror via reactive ion etching processes.

DOI： 10.35848/1347-4065/ac5d25

Language：Japanese  

令和3年度宇宙輸送シンポジウム（2022年1月13日-14日. オンライン開催)
Space Transportation Symposium FY2021 (January 13-14, 2022. Online Meeting)
資料番号: SA6000173070
STEP-2021-031

Language：Japanese   Publishing type：Research paper (scientific journal)  

Design of Ion Engine Grid System Using Genetic Algorithm and Visualization of Searching Process

DOI： DOI https://doi.org/10.2322/astj.20.47

Language：Japanese   Publishing type：Research paper (scientific journal)  

Neutralization Performance with Two Field Emission Cathodes in an Ion Engine

DOI： https://doi.org/10.2322/jjsass.69.215

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.2322/tjsass.64.288

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.35848/1347-4065/abfadc

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI https://doi.org/10.2322/tjsass.64.189

Language：Japanese   Publishing type：Research paper (scientific journal)  

Neural Network Prediction of Discharge Current using Plume shape and Operational Parameters in Hall Thrusters

DOI： DOI https://doi.org/10.2322/astj.20.47

Repository Public URL： http://hdl.handle.net/2324/4377921

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI https://doi.org/10.2322/tastj.19.81

Repository Public URL： http://hdl.handle.net/2324/4377905

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI https://doi.org/10.2322/tastj.19.75

Repository Public URL： http://hdl.handle.net/2324/4377911

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.5127788

Repository Public URL： http://hdl.handle.net/2324/4103905

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.5127788

Language：English   Publishing type：Research paper (scientific journal)  

A hollow cathode is an efficient electron source in the self-heating mode utilizing the discharge power. However, in sub-ampere currents, it needs keeper power to maintain the thermionic electron discharge, which could decrease the thrust efficiency. To address this problem, we propose using a microwave cathode, which is based on the flight model of a microwave ion thruster neutralizer cathode, as an alternative to a hollow cathode. First, we redesigned the magnetic field of a microwave cathode discharge chamber and tested it in the diode mode configuration. The electron emission current is doubled compared to the original performance. Next, we coupled the improved microwave cathode with a 200-W class Hall thruster and compared the characteristics and performance with a hollow cathode. We confirmed that the magnetic field polarity affects the ignition characteristics. We measured the thrust by an inverted thrust stand, the ion energy distribution functions by a retarding potential analyzer, and the beam profiles by an ion collector. The thrust and thrust efficiency are equivalent for both types of cathode. The specific impulse is 10% higher in the case of the microwave cathode. Since the potential difference between the microwave cathode and ground rapidly increased at currents above 600 mA, this could be taken to be the trade-off point against the hollow cathode.

DOI： 10.1016/j.actaastro.2020.06.049

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.actaastro.2020.06.049

Repository Public URL： http://hdl.handle.net/2324/4377904

Language：English  

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.

DOI： 10.1016/j.hedp.2020.100814

Repository Public URL： http://hdl.handle.net/2324/4377903

Language：English  

Two-Dimensional Thomson Scattering Measurement for the Investigation of Electron and Ion Detachment from an External Magnetic Field

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

The neutralization of a miniature ion thruster using xenon as a
propellant with field emission neutralizer was successfully
demonstrated using an FEC with carbon nanotube emitter for, to
our knowledge, the first time. The emission current from the FEC is
balanced with the ion beam current from the ion thruster head, by
changing the potential of the neutralizer relative to the chamber
(space plasma potential). The electrically isolated potential of the
cathode is kept constant and is changed by changing the ion beam
current and the gate voltage. The electron emission cost was 360 W/
A. This is higher than that of a conventional hollowcathode (less than
30 W/A) [26,27], but considering the current range and the lack of
propellant consumption, this is a competitive cost. A remaining
challenge is demonstration of the 30 W class miniature ion thruster
with CNT-FEC and the life expectancy of the FEC with carbon
nanotube.

DOI： 10.2514/1.B37214

Language：English   Publishing type：Research paper (scientific journal)  

Portable and noise-tolerant magnetic field generation system
© 2018 Author(s). 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.

DOI： 10.1063/1.5049217

Language：English  

Development of Variable Time-Averaged Thrust System by Controlling Duty Ratio of Ion Beam Extraction in Ion Thrusters

DOI： 10.2322/tastj.16.388

Language：English   Publishing type：Research paper (scientific journal)  

Experimental demonstration of ion extraction from magnetic thrust chamber for laser fusion rocket
A magnetic thrust chamber is an important system of a laser fusion rocket, in which the plasma kinetic energy is converted into vehicle thrust by a magnetic field. To investigate the plasma extraction from the system, the ions in a plasma are diagnosed outside the system by charge collectors. The results clearly show that the ion extraction does not strongly depend on the magnetic field strength when the energy ratio of magnetic field to plasma is greater than 4.3, and the magnetic field pushes back the plasma to generate a thrust, as previously suggested by numerical simulation and experiments.

Language：English   Publishing type：Research paper (scientific journal)  

Thomson Scattering Measurement of Laser-Produced Plasma in a Magnetic Thrust Chamber
Laser fusion rocket is one of the candidate propulsion devices for Mars exploration. It obtains thrust from the interaction between plasma and magnetic field and this propulsion system is called magnetic thrust chamber. We constructed a spectrometer with high wavelength resolution of 35 pm to obtain plasma parameters by measuring ion feature of laser Thomson scattering from a laser-produced plasma in a magnetic thrust chamber. We obtain the plasma parameters such as electron temperature, electron density, and velocity as well as the plasma density structure showing the stagnation of the plasma by magnetic field. (C) 2018 The Japan Society of Plasma Science and Nuclear Fusion Research.

DOI： 10.1585/pfr.13.1306016

Language：English   Publishing type：Research paper (scientific journal)  

Three different types of high power Hall thrusters—anode layer type, magnetic layer type with high specific impulse, and magnetic layer type with dual mode operation (high thrust mode and high specific impulse mode)—have been developed, and the thrust performance of each thruster has been evaluated. The thrust of the anode layer type thruster is in the range of 19–219 mN, with power in the range of 325–4500 W. The thrust of the high specific impulse magnetic layer type thruster was 102 mN, with specific impulse of 3300 s. The thrust of the bimodal operation magnetic layer thruster was 385 mN with specific impulse of 1200 s, and 300 mN with specific impulse of 2330 s. The performance of these thrusters demonstrates that the Japanese electric propulsion community has the capability to develop a thruster for commercial use.

DOI： 10.2322/tjsass.60.320

Language：English  

Magnetic reconnection experiment with an external magnetic field by using Gekko-XII laser

Language：English   Publishing type：Research paper (scientific journal)  

Control of unsteady laser-produced plasma-flow with a multiple-coil magnetic nozzle
We report an experimental demonstration of controlling plasma flow direction with a magnetic nozzle consisting of multiple coils. Four coils are controlled separately to form an asymmetric magnetic field to change the direction of laser-produced plasma flow. The ablation plasma deforms the topology of the external magnetic field, forming a magnetic cavity inside and compressing the field outside. The compressed magnetic field pushes the plasma via the Lorentz force on a diamagnetic current: j × B in a certain direction, depending on the magnetic field configuration. Plasma and magnetic field structure formations depending on the initial magnetic field were simultaneously measured with a self-emission gated optical imager and B-dot probe, respectively, and the probe measurement clearly shows the difference of plasma expansion direction between symmetric and asymmetric initial magnetic fields. The combination of two-dimensional radiation hydrodynamic and three-dimensional hybrid simulations shows the control of the deflection angle with different number of coils, forming a plasma structure similar to that observed in the experiment.

DOI： 10.1038/s41598-017-09273-3

Language：Japanese  

Operation Characteristics of 5-kW Class RAIJIN Hall Thruster
A Hall thruster system for in-space propulsion has been developed as a part of a Japanese collaborative research and development project aiming at practical use of a high power anode layer type Hall thruster. Its thrust was measured at the ISAS/JAXA vacuum chamber facilities using a dual-pendulum thrust stand developed at the University of Tokyo. In the low specific impulse mode operation, thrust efficiency of 64% and thrust to power ratio of 80mN/kW were achieved. In the high specific impulse mode operation, the thruster was successfully operated at the acceleration voltage of up to 1,000V.

DOI： 10.2322/jjsass.65.82

Language：English   Publishing type：Research paper (scientific journal)  

DOI： http://doi.org/10.2322/tastj.14.Pb_183

Language：English   Publishing type：Research paper (scientific journal)  

A miniature electron cyclotron resonance (ECR) plasma source is operated as a neutralizer, and the effect of orifice diameter on the output is studied. The output is quite promising for accompanying 1-mN-class ion thrusters with an output ion-beam current of 12–15mA. The optimum orifice diameter is independent of neutral mass flow rate, implying that factors other than electron-neutral collisions are dominant. The variation in orifice diameter is expected to alter the microwave field boundary conditions inside discharge chamber (DC), and also influence the dc-electric field existing between the orifice and collector. The convolution of these two factors would be primarily responsible for the optimum orifice diameter.

DOI： 10.2322/tjsass.60.259

Language：English   Publishing type：Research paper (scientific journal)  

The approach presented in a study uses the laser Rayleigh scattering technique. This is a non-intrusive method, and it does not disturb the plasma and neutral flow. Number densities can be measured quantitatively by calibration using 10⁴ Pa nitrogen, so a complicated collisional-radiative model is not required. The Rayleigh scattering spectrum reflects the velocity distribution of the atoms, so propellant xenon atoms can be distinguished from the ambient xenon atoms. In addition, even when both ions and electrons are present, the neutral number density can be estimated, since the scattering spectrum is a convolution of Rayleigh and Thomson spectra.

DOI： 10.2322/tjsass.60.327

Repository Public URL： http://hdl.handle.net/2324/4377920

Language：English  

Development of a Miniature Microwave Discharge Thruster
<p>A miniature microwave discharge plasma thruster for micro satellites is under development, with the target power consumption, thrust and specific impulse of 10 W, 1 mN and 1000 sec, respectively. Thrust was estimated from the measured ion beam current and ion energy distribution function using an ion collector and a retarding potential analyzer. Several parameters, including antenna configuration, length of the discharge chamber and configuration, were optimized for the improvement of the thrust performance. The overall thrust was estimated to be 82 &mu;N at the incident microwave power of 10 W and the mass flow rate of 82 &mu;g/sec.</p>

DOI： 10.2322/tastj.14.Pb_141

Language：Japanese  

Numerical Study of On-Off Thrust Control of Ion Engine

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： http://doi.org/10.2322/tastj.14.Pb_173

Language：English  

Measurement of Aluminum Erosion Rate by Cavity Ring-Down Spectroscopy
<p>A cavity ring-down spectroscopy method to measure sputter erosion and estimate the lifetime of electric propulsion systems was developed. We measured sputtered aluminum atoms from the acceleration grid of an ion thruster. An external-cavity diode laser was used as the probe laser to measure the aluminum transition line from ground state to upper state, at 394.512 nm (vacuum). The erosion rate of the acceleration grid was estimated to be 259 ± 99 ng/s. </p>

DOI： 10.2322/tastj.14.Pb_111

Language：Others   Publishing type：Research paper (other academic)  

Development of a magnetic thrust chamber for a laser fusion rocket
We have conducted numerical researches to validate a thrust vector control system for a laser fusion rocket. Proposed system is the multi coil magnetic thrust chamber. We used the two-dimensional radiation hydrodynamics code and the three-dimensional hybrid code to calculate a laser irradiation and an interaction between magnetic fields and plasmas, respectively. We have numerically succeeded in controlling the vector of plasma flow by changing of magnetic field configurations.

DOI： 10.2514/6.2016-4684

Language：Others  

Measurement of Electron and Neutral Atom Density Downstream of an Electric Propulsion

DOI： 10.2514/6.2016-5036

Language：English   Publishing type：Research paper (other academic)  

We demonstrate a magnetic thrust chamber system, in which an expanding plasma is controlled by an external magnetic field to produce a thrust. The plasma structure and energy dependences are discussed in terms of the drive laser energy and magnetic field strength. The density distribution from two different experiments show identical structure despite the laser energy is different by two order of magnitude when the ratio of magnetic field to plasma energy is more or less same. The experimental results indicate that this ratio is one of the essential factors to extrapolate the plasma dynamics for much larger energy such as inertial confinement fusion plasmas.

DOI： 10.1088/1742-6596/717/1/012071

Language：English  

We have built a sputter erosion sensor using Cavity Ring-Down Spectroscopy (CRDS) for validating the numerical analysis tool called ''JIEDI tool''. In this paper, we measured the velocity distribution function of the aluminum atoms sputtered from an aluminum acceleration grid of the ion thruster. The experimentally obtained aluminum velocity distribution have been found to be compatible with those calculated by the numerical analysis method.

DOI： 10.1088/1748-0221/11/01/C01079

Language：English   Publishing type：Research paper (scientific journal)  

Magnetic thrust chamber is a propulsion system controlling plasma by a magnetic field and is expected as a propulsion system of laser fusion rocket. This rocket obtains thrust due to the interaction between plasma and magnetic field in the system. We examine the plasma structure in a magnetic thrust chamber by observing the light emission from the plasma with several magnetic field strength. The experiments imply that anisotropic plasma expansion is induced by the applied magnetic field and the velocity is decreased at the magnetic field above 0.67 T.

DOI： 10.1585/pfr.11.3406012

Language：English   Publishing type：Research paper (scientific journal)  

A one hundred hour test of a 100mA class microwave discharge neutralizer was performed to investigate the erosion rate and deposition in the neutralizer. The mass loss of each component (antenna, discharge chamber wall, front yoke, back yoke, insulator and orifice) was measured in diode mode (contact voltage of 50 V) at a constant incident microwave power of 8W and xenon mass flow rate of 49 μg/s. The measured erosion rates of the discharge chamber and the antenna were 180 μg/hr and 10 μg/hr, respectively. The element concentration of the deposited material on the back yoke and insulator were measured; the contamination on the insulator was found to contain 34% copper from the wall and 6% molybdenum from the antenna.

DOI： 10.2322/tjsass.59.100

Language：English   Publishing type：Research paper (scientific journal)  

A miniature microwave electron cyclotron resonance plasma source [(discharge diameter)/(microwave cutoff diameter) < 0.3] has been developed at Kyushu University to be used as an ion thruster in micro- propulsion applications in the exosphere. The discharge source uses both radial and axial magnetostatic field confinement to facilitate electron cyclotron resonance and increase the electron dwell time in the volume, thereby enhancing plasma production efficiency. Performance of the ion thruster is studied at 3 microwave frequencies (1.2 GHz, 1.6 GHz, and 2.45 GHz), for low input powers (< 15 W) and small xenon mass flow rates (< 40 mu g/s), by experimentally measuring the extracted ion beam current through a potential difference of congruent to 1200 V. The discharge geometry is found to operate most efficiently at an input microwave frequency of 1.6 GHz. At this frequency, for an input power of 8 W, and propellant (xenon) mass flow rate of 21 mu g/s, 13.7 mA of ion beam current is obtained, equivalent to an calculated thrust of 0.74 mN. (C) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4937353

Language：English   Publishing type：Research paper (scientific journal)  

Acceleration of Miniature Targets by Kilo-Tesla Magnetic Field
The first demonstration of target acceleration by a strong magnetic field is conducted. Two miniature targets, a gold ball and a neodymium permanent magnet, are accelerated by a magnetic field. A magnetic-field strength as high as 1 kT is produced using a capacitor-coil in which two copper disks are connected by a single-turn coil, and the capacitor was driven by two beams from the GEKKO-XII high-power laser. The targets are accelerated by the interaction force between two magnetic moments: the target and the capacitor-coil. The velocity of the accelerated gold ball was estimated as 10 m/s from shadowgraphy images. In the case of the magnet, although the image could not be observed clearly due to the plasma generated around the magnet, it was confirmed that the magnet interacts with the magnetic field of the capacitor-coil.

DOI： 10.2322/tastj.13.17

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

A new pulse-synchronous driver system is proposed for Hall thrusters. By applying a pulsating drive voltage with a frequency close to that of the discharge oscillation, the stable and synchronized operation of a Hall thruster can be realized. A pulsating boost chopper circuit is also proposed that is suitable for use as a pulse-synchronous drive and has many attractive features as the driver circuit for Hall thrusters. Moreover, it is demonstrated that the thrust performance is improved approximately 30&#37; at 200 W input power by using the driver circuit. Pulse-synchronous driving is a new driving method optimized for thruster operation, and it is expected to become an essential technology for high-power Hall thrusters.

DOI： 10.2514/1.B35273

Language：English  

A newly developed power processing unit (PPU) offers the advantages of smaller size and lighter weight than conventional PPUs. The thrust performance of a magnetic layer type Hall thruster developed at Kyushu University with this new PPU was investigated; it showed a good performance as compared with conventional power supplies. The thrust to power ratio was improved to 58 mN/kW at discharge voltage of 150 V and anode xenon mass flow rate of 1.0 mg/s.

DOI： 10.1109/TPS.2014.2370066

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

A miniature microwave plasma source employing both radial and axial magnetic fields for plasma confinement has been developed for micro-propulsion applications. Plasma is initiated by launching microwaves via a short monopole antenna to circumvent geometrical cutoff limitations. The amplitude and phase of the forward and reflected microwave power is measured to obtain the complex reflection coefficient from which the equivalent impedance of the plasma source is determined. Effect of critical plasma density condition is reflected in the measurements and provides insight into the working of the miniature plasma source. A basic impedance calculation model is developed to help in understanding the experimental observations. From experiment and theory, it is seen that the equivalent impedance magnitude is controlled by the coaxial discharge boundary conditions, and the phase is influenced primarily by the plasma immersed antenna impedance. (C) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4894476

Language：Japanese  

DOI： 10.2322/jjsass.62.123

Language：English  

Development of a Low Power Multipole Confined Microwave Plasma Ion Thruster
A modified magnetic multipolar plasma source is developed and tested for application as an ion thruster for space propulsion. The configuration consists of eight samarium-cobalt bar-magnets, symmetrically surrounding a cylindrical discharge volume of 21 mm diameter, with their magnetization in the radial direction. A donut magnet is placed at one axial end of the discharge volume with its magnetization along the cylindrical axis. A short monopole antenna, coaxial with the donut magnet is used for launching microwaves in the discharge volume. The resulting magnetic configuration due to the radial and axial magnetic fields, help in generation and sustenance of microwave induced electron cyclotron resonance plasma. Ions are extracted from the plasma by high voltage grids, attached to the end, opposite to the donut magnet. Two different magnetic configurations obtained by reversing the magnetization direction of the donut magnet are compared. Three dimensional magnetic field simulations and ion saturation current measurements at various microwave frequencies are used to determine the optimum magnetic configuration. Ion beam current extraction measurements, using the grids is carried out. Typical ion beam current of 9.9 mA is obtained, with calculated thrust of 0.63 mN at 8 W for 1600 MHz, with a Xenon mass flow rate of 20 μg/s.

DOI： 10.2322/tastj.12.Pb_7

Language：English  

A continuous-wave cavity ring-down spectroscopy sensor for real-time measurements of sputtered boron from Hall thrusters has been developed. The sensor uses a continuous-wave frequency-quadrupled diode laser at 250 nm to probe ground state atomic boron sputtered from the boron nitride insulating channel. Validation results from a controlled setup using an ion beam and target showed good agreement with a simple finite-element model. Application of the sensor for measurements of two Hall thrusters, the H6 and SPT-70, is described. The H6 was tested at power levels ranging from 1.5 to 10 kW. Peak boron densities of 10 ± 2 × 10¹⁴ m^-3 were measured in the thruster plume, and the estimated eroded channel volume agreed within a factor of 2 of profilometry. The SPT-70 was tested at 600 and 660 W, yielding peak boron densities of 7.2 ± 1.1 × 10¹⁴ m^-3, and the estimated erosion rate agreed within ∼20&#37; of profilometry. Technical challenges associated with operating a high-finesse cavity in the presence of energetic plasma are also discussed.

DOI： 10.1063/1.4879135

Language：English   Publishing type：Research paper (scientific journal)  

To confirm the validity of the modified numerical simulation performing a series of numerical simulations for highenergy laser injection onto a spherical target and the ablation plasma behavior in a magnetic field, the modified numerical simulation is compared with experiments and original numerical simulation. The modified numerical simulation consists of a one-dimensional Lagrangian radiation hydrodynamic code to calculate the creation process of laser-produced plasma and a three-dimensional hybrid particle-in-cell code. The original numerical simulation does not consider the creation process. The measured impulse bit due to the interaction between the diamagnetic current in a laser-produced plasma and the magnetic field generated by neodymium permanent magnets is 2.42 ± 0.23 μN · s. The calculated impulse bit in the modified and original numerical simulations is 10.3 and 72.7 μN · s, respectively. These results reveal that the modified numerical simulation models closer to the experiment than the original numerical simulation. In addition, to investigate the effect of the magnetic field strength on the plasma behavior in a magnetic thrust chamber system for a laser fusion rocket, the modified numerical simulation is performed. As a result, it is revealed that there is an approximation region of the magnetic field strength for high thrust performance.

DOI： 10.2514/1.B34911

Language：Japanese  

Language：English  

For the purpose of removal of tritium retained in tungsten (W), pulsed laser irradiation has been applied. The laser light used here was the fourth harmonic of Nd: YAG laser (wavelength; 266 nm, pulse width; 20 ps, pulse frequency; 10 Hz, laser energy up to 3 mJ/pulse). Samples were pure W plates and those saturated with D by D2+ ion implantation at room temperature with using a 2.5 keV ion gun. Released ions and molecules by the laser irradiation were measured by a time-of-flight mass spectrometer (TOFMS) and a quadrupole mass spectrometer (Q-mass), respectively. Ablation of W was observed by the laser irradiation with a deposited power density above 1.5 × 10¹¹ W/cm² (3 J/cm²/pulse) (an ablation threshold) and D removals below and above the ablation threshold were quite different. The most effective removal of tritium retained in W could be realized by the pulsed laser irradiation with the power density of just below the ablation threshold.

DOI： 10.1016/j.jnucmat.2013.07.047

Language：English   Publishing type：Research paper (scientific journal)  

Analysis of Laser Wavelength and Energy Dependences of the Impulse in a Magnetic Thrust Chamber System for a Laser Fusion Rocket
Experiments using a pendulum thrust stand are performed to determine the dependences of the impulse on the laser wavelength and energy in a magnetic thrust chamber system for a laser fusion rocket. The impulse is generated by the interaction between a diamagnetic current in a laser-produced plasma and a magnetic field. The plasma is produced by irradiating a spherical polyacetal target with a single-beam glass laser (laser pulse duration: 1.3 ns; laser wavelengths: 1,053, 527 and 351 nm; laser energy: 30–900 J). The magnetic field is generated by a cylindrical neodymium permanent magnet (50 mm diameter and 40 mm long) placed in a position 33 mm from the target. Impulses in the range 0.02–10 mNs are measured using a pendulum thrust stand. The experiments reveal that the impulse for 2ω is similar to that for 3ω, and is larger than that for ω.

DOI： 10.2322/tjsass.56.170

Language：English  

DOI： 10.2322/tastj.10.Pb_109

Language：English   Publishing type：Research paper (scientific journal)  

Laboratory generation of strong magnetic fields opens new frontiers in plasma and beam physics, astro- and solar-physics, materials science, and atomic and molecular physics. Although kilotesla magnetic fields have already been produced by magnetic flux compression using an imploding metal tube or plasma shell, accessibility at multiple points and better controlled shapes of the field are desirable. Here we have generated kilotesla magnetic fields using a capacitor-coil target, in which two nickel disks are connected by a U-turn coil. A magnetic flux density of 1.5 kT was measured using the Faraday effect 650 mu m away from the coil, when the capacitor was driven by two beams from the GEKKO-XII laser (at 1 kJ (total), 1.3 ns, 0.53 or 1 mu m, and 5 x 10(16) W/cm(2)).

DOI： 10.1038/srep01170

Language：English   Publishing type：Research paper (scientific journal)  

We have installed a new system to observe cathodoluminescence (CL) in a high voltage transmission electron microscope (HVTEM). The system is constructed of a ball lens for collection of CL, an optical fiber and a multi-channel optical detector. The system can be operated without any disturbance of TEM observation. The system was proved to be very useful to observe CL in HVTEM and will be a powerful tool to investigate production mechanisms of luminescence centers by observing CL changes with incident electron energy and flux (displacement damage effect), and temperature, together with simultaneous TEM observations of microstructure changes.

DOI： 10.2320/matertrans.M2013025

Language：English   Publishing type：Research paper (scientific journal)  

Numerical Analysis of Magnetic Thrust Chamber System for Laser Fusion Rocket Considering the Creation Process of Laser-Produced Plasma
The plasma behavior in a magnetic thrust chamber system for a laser fusion rocket is numerically simulated using a three-dimensional (3D) hybrid particle-in-cell (PIC) code and a one-dimensional (1D) radiation hydrodynamic code. The magnetic thrust chamber and an applied magnetic field with a suitable geometry generate an impulse from the interaction between the diamagnetic current in the laser-produced plasma and the magnetic field generated by a magnetic coil. A 1D radiation hydrodynamics code is used to compute the hydrodynamic evolution of a radiating plasma heated by laser beams or external radiation sources. By combining this code and a 3D hybrid PIC code, a series of numerical simulations are performed to investigate high-energy laser injection onto a fuel target and the ablated plasma behavior of the system. A thrust energy of 0.37 J and an impulse bit of 31.6 μNs are obtained for an incident laser energy of 4.0 J. This impulse bit could mostly be generated by interactions between a slowly expanding plasma (expansion velocity of ~20 km/s) and a magnetic field. To optimize this system, it is important to reduce the expansion velocity of the laser-produced plasma.

DOI： 10.2322/tastj.10.Pb_71

Language：English   Publishing type：Research paper (scientific journal)  

Thomson scattering diagnostics in the plasma of an ion thruster

Language：Japanese  

Effect of Mesh Size and Time Step on Simulation Results of Ion Acceleration Grid Erosion

Language：English  

Language：English  

High efficiency control method for the hall thruster system through constant flow rate control by power supply control
We present a new power supply control method, which achieves constant flow Rate control for the thrust of a 20 mN-class Hall thruster. First, we present observations of a 20mN-class Hall thruster with oscillation-mode-map. We make a theoretical study of the thrust and experiments on electrical characteristics of the Hall thruster, and conclude that thrust, thrust efficiency and low frequency oscillation are clearly determined by the external control parameters, anode voltage, gas flow rate, and magnetic flux density. Second, we discuss how to control the power supplies to suppress the power consumption, especially when the operation or thruster conditions change temporarily during use. The new method will be a very important guideline for Hall thruster system design and operation, in particular making it easy to manage the power consumption in a satellite by controlling the thrust resources. As a result of performance experiments for a 20mN-class Hall thruster, over 36&#37; thrust efficiency of the Hall thruster was found to be sensitive to the anode voltage and applied magnetic flux density. The new power control method achieves constant flow rate control method of the thrust. The benefits are light weight and low cost.

DOI： 10.1587/transcom.E95.B.133

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)  

An experiment is conducted to measure an impulse for demonstrating a magnetic thrust chamber system for laser fusion rocket. The impulse is produced by the interaction between plasma and magnetic field. In the experiment, the system consists of plasma and neodymium permanent magnets. The plasma is created by a single-beam laser aiming at a polystyrene spherical target. The impulse is 1.5 to 2.2 mu Ns by means of a pendulum thrust stand, when the laser energy is 0.7 J. Without magnetic field, the measured impulse is found to be zero. These results indicate that the system for generating impulse is working. (C) 2011 American Institute of Physics. [doi:10.1063/1.3626600]

DOI： 10.1063/1.3626600

Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

A study was conducted to measure plasma properties by laser Thomson scattering (LTS) to understand the physics inside this engine. The photon-counting method with a double monochromator was used to overcome the difficulties of applying the method to the plasma produced in the miniature microwave ion engine. Microwave power at 2.45 GHz was fed through a coaxial line and into an antenna in the engine. The screen grid and the ion source body were biased at +1500 V relative to ground and the acceleration grid was biased at -300 V. The primary electrons were confined in the mirrorlike magnetic field formed between the central and front yokes, gaining energy from microwave emission by electron cyclotron resonance heating. Two small holes to inject the laser and another hole collect scattering light were made to measure the plasma inside the discharge chamber.

DOI： 10.2514/1.39145

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (other academic)  

Preliminary Experiments for Demonstrating Magnetic Nozzle Concept in Laser Fusion Rocket

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2322/tstj.7.Pb_119

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2322/tstj.7.Pb_155

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2322/tstj.7.Pb_1

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.2995765

Language：Japanese   Publishing type：Research paper (scientific journal)  

Dependence of Thruster Configuration on Thrust Performance in Miniature Ion Thruster

DOI： 10.2322/jjsass.56.383

Language：English   Publishing type：Research paper (scientific journal)  

We describe the use of cavity ring-down spectroscopy for measurement of number densities of sputtered particles. Applications for thruster characterization in electric propulsion and process monitoring in plasma engineering are discussed.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2514/1.22410

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2322/tjsass.48.169

Repository Public URL： http://hdl.handle.net/2324/5841

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.2001630

Repository Public URL： http://hdl.handle.net/2324/5840

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Number Density Measurement of Oxygen Atoms in a Hall-Type Ion Source
Plume

Naoji YAMAMOTO, Takafumi NAKAGAWA, Makoto MATSUI, Kimiya KOMURASAKI
and Yoshihiro ARAKAWA

Language：Japanese   Publishing type：Research paper (scientific journal)  

Experimental Investigation of a Hall Thruster using Oxygen as the propellant

Takafumi NAKAGAWA, Naoji YAMAMOTO, Makoto MATSUI, Kimiya KOMURASAKI
and Yoshihiro ARAKAWA

Repository Public URL： http://hdl.handle.net/2324/16995

Language：Japanese   Publishing type：Research paper (scientific journal)  

Ion Beam Characteristics in Hall Accelerators Using Oxygen Gas

Naoji YAMAMOTO, Takafumi NAKAGAWA, Kimiya KOMURASAKI and Yoshihiro ARAKAWA

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Characteristics of plasma fluctuations at the frequencies 10-100 kHz in Hall thrusters were investigated since the fluctuations might affect not only its performance but also its lifetime. Measured fluctuation characteristics varied with magnetic flux density of the applied field and they were categorized into the four regimes. Since the electron mobility strongly depends on applied field strength, it was thought that electrons would play an important role on this oscillation. Therefore, the oscillation model derived from ionization instability considering electron mobility was proposed. The predicted stable/unstable operating condition map agreed well with the measured one.

DOI： 10.1016/S0042-207X(01)00445-6

Language：Japanese   Publishing type：Research paper (scientific journal)  

Relation between Discharge Oscillations and Performance in Hall Accelerators

Naoji YAMAMOTO, Takafumi NAKAGAWA, Kimiya KOMURASAKI, and Yoshihiro ARAKAWA

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Discharge Oscillations in Hall Thrusters

Naoji Yamamoto, Kimiya Komurasaki, and Yoshihiro Arakawa

Language：English   Publishing type：Research paper (international conference proceedings)  

Presentation type：Oral presentation (general)  

Venue：Nikko   Country：Japan  

Event date： 2039.1

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Venue：相模原   Country：Japan  

Event date： 2015.7

Language：English  

Venue：kobe, Hyogo   Country：Japan  

Other Link： http://www.ists.or.jp/2015/

Event date： 2015.7

Language：English   Presentation type：Oral presentation (general)  

Venue：kobe, Hyogo   Country：Japan  

Other Link： http://www.ists.or.jp/2015/

Event date： 2015.2

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Venue：神奈川県相模原市   Country：Japan  

Event date： 2015.1

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Venue：神奈川県相模原市   Country：Japan  

Event date： 2014.11

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Venue：Niigata, Niigata   Country：Japan  

Event date： 2013.10

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Venue：the George Washington University in Washington, D.C., USA.   Country：United States  

Event date： 2013.10

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Venue：the George Washington University in Washington, D.C., USA.   Country：United States  

Event date： 2013.10

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Venue：the George Washington University in Washington, D.C., USA.   Country：United States  

Event date： 2013.6

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Venue：Nagoya, Aichi   Country：Japan  

Event date： 2013.3

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Country：Japan  

Event date： 2013.1

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Venue：神奈川県相模原市   Country：Japan  

Event date： 2012.11

Language：Japanese  

Venue：大分県別府市   Country：Japan  

Event date： 2012.7 - 2012.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Atlanta, Georgia,   Country：United States  

Event date： 2012.4

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Venue：大阪   Country：Japan  

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Venue：福岡   Country：Japan  

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Venue：相模原   Country：Japan  

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Venue：相模原   Country：Japan  

Event date： 2011.11 - 2011.12

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Venue：松山   Country：Japan  

Event date： 2011.11 - 2010.11

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Event date： 2011.11

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Venue：柳川   Country：Japan  

Event date： 2011.9

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Venue：箱根   Country：Japan  

Event date： 2011.9

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Venue：Wiesbaden   Country：Germany  

Event date： 2011.9

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Venue：Wiesbaden   Country：Germany  

Event date： 2011.9

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Venue：Wiesbaden   Country：Germany  

Event date： 2011.3

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Venue：広島   Country：Japan  

Event date： 2011.1

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Venue：相模原   Country：Japan  

Event date： 2011.1

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Venue：相模原   Country：Japan  

Event date： 2010.11

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Venue：静岡   Country：Japan  

Event date： 2010.11

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Venue：静岡   Country：Japan  

Event date： 2010.9

Language：Others   Presentation type：Oral presentation (general)  

Venue：Ohrid, Republic of Macedonia   Country：Other  

Country：Japan  

Country：Japan  

Country：Japan  

Country：Japan  

Country：Japan  

Presentation type：Oral presentation (general)  

Venue：miyazaki   Country：Japan  

Development of Microwave Discharge Ion Engine by using Monopole

Presentation type：Oral presentation (general)  

Venue：miyazaki   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Miyazaki,   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Fukuoka,   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Presentation type：Symposium, workshop panel (public)  

Venue：福岡,   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：福井   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Kitakyushu,   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：相模原   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：名古屋   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：相模原   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：相模原   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Kitakyushu,   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Kitakyushu,   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Fukuoka   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Fukuoka   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Princeton University,   Country：United States  

Presentation type：Oral presentation (general)  

Venue：広島   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：相模原   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：相模原   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

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Venue：福岡   Country：Japan  

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Venue：Beijing   Country：China  

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Venue：Kanazawa,   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Kanazawa,   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Kanazawa,   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：Sacramento, California   Country：United States  

Presentation type：Oral presentation (general)  

Venue：Zvenigorod,   Country：Russian Federation  

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Venue：Pusan National. Univ.   Country：Korea, Republic of  

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Venue：福岡   Country：Japan  

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Venue：福岡   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：福岡   Country：Japan  

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Venue：福岡   Country：Japan  

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Venue：福岡   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：大阪   Country：Japan  

Presentation type：Symposium, workshop panel (public)  

Venue：相模   Country：Japan  

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Venue：相模原   Country：Japan  

Presentation type：Symposium, workshop panel (public)  

Venue：相模原   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：姫路   Country：Japan  

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Venue：姫路   Country：Japan  

Presentation type：Oral presentation (general)  

Venue：姫路   Country：Japan  

Presentation type：Oral presentation (general)  

Country：Japan  

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Country：Japan  

Presentation type：Oral presentation (general)  

Country：Japan  

Venue：Florence   Country：Italy  

Venue：Florence   Country：Italy  

Venue：Florence   Country：Italy  

Venue：Florence   Country：Italy  

Venue：Florence   Country：Italy  

Country：Japan  

Country：Japan  

Presentation type：Oral presentation (general)  

Country：Japan  

Presentation type：Oral presentation (general)  

Country：Japan  

Country：Japan  

Venue：相模原   Country：Japan  

Country：Japan  

Venue：相模原   Country：Japan  

Venue：St. Petersburg, FL   Country：United States  

Venue：Hamamatsu   Country：Japan  

Venue：Hamamatsu   Country：Japan  

Venue：Hamamatsu   Country：Japan  

Venue：Hamamatsu   Country：Japan  

Venue：Hartford, CT   Country：United States  

Venue：Hartford, CT   Country：United States  

Venue：Hamamatsu   Country：Japan  

Venue：相模原   Country：Japan  

Venue：Santa Clara, CA   Country：United States  

Venue：長崎   Country：Japan  

Venue：吹田   Country：Japan  

Venue：筑波   Country：Japan  

Venue：Ann Arbor   Country：United States  

Venue：Ann Arbor   Country：United States  

Venue：Ann Arbor   Country：United States  

Venue：Ann Arbor   Country：United States  

Venue：茨木   Country：Japan  

Venue：北九州   Country：Japan  

Venue：茨木   Country：Japan  

Venue：相模原   Country：Japan  

Venue：相模原   Country：Japan  

Venue：宮崎   Country：Japan  

Language：Others   Presentation type：Oral presentation (general)  

Venue：吹田   Country：Japan  

Language：Japanese  

Thrust Performance of a 200 W Class Hall Thruster
A 200 W class Hall thruster has been developed for the small satellites main propulsion. In order to overcome the degradation owing to the miniaturization, it has a unique magnetic field configuration, similar to “magnetic shielding”. The thrust performance was measured using a pendulum thrust stand. The thrust, thrust to power ratio, thrust efficiency is achieved to 13.1 mN,56 mN/kW and 0.36, respectively at discharge voltage of 300 V, xenon mass flow rate of 1.0 mg/s. The obtained thrust performance is comparable to the other 200 W class thruster.

DOI： 10.34377/aps.25.2_85

Language：Japanese  

DOI： 10.14822/kjsass.65.8_236

Language：Japanese  

Feasibility Study of Valuable Thrust Ion Thrusters by Controlling Ion Beam Extraction Duty Ratio
Space Transportation Symposium FY2016 (January 19-20, 2017. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan

Language：Japanese  

Transient Simulation of On-Off Control of Ion Beam Extraction
Space Transportation Symposium FY2016 (January 19-20, 2017. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan

Language：Japanese  

Thrust Prediction Code Using Neural Network for Auto Controlling System in Hall Thrusters

Language：Japanese  

磁気スラストチャンバーによるプラズマ排出制御の実験的検証

Language：Japanese  

Collaborative Development of 5-kW Class RAIJIN Hall Thruster

Language：Japanese  

小型イオンエンジンを用いた新しい磁場計測の構築

Language：Japanese  

磁気ノズルにおける推力発生の原理実証実験

Language：Japanese  

Development of Numerical Analysis Tool for Grid Erosion Intensity Measurement by CRDS Method
Space Transportation Symposium FY2015 (January 14-15, 2016. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan

Language：Japanese  

大型レーザー生成プラズマを用いた磁気ノズルによる推進システムの模擬実験

Language：Japanese  

Numerical Analysis on Internal plasma potential in Microwave Discharge Neutralizer with weak coupled analysis

Language：Japanese  

Dependence of circuit parameters on a thrust performance in a Hall thruster using a pulsating boost chopper circuit

Language：Japanese  

Darkening of fused silica glass in strong magnetic field generation experiment

Language：Japanese  

平成24年度宇宙輸送シンポジウム (2013年1月17日-1月18日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)), 相模原市, 神奈川県形態: カラー図版あり形態: PDF資料番号: AA0061856134レポート番号: STEP-2012-051

Language：Japanese  

Generation of extreme B-field by laser-driven and its application

Language：Others  

Measurement of xenon plasma properties in an ion thruster using laser Thomson scattering technique
This paper reports on the development of a method for measuring xenon plasma properties using the laser Thomson scattering technique, for application to ion engine system design. The thresholds of photo-ionization of xenon plasma were investigated and the number density of metastable atoms, which are photo-ionized by a probe laser, was measured using laser absorption spectroscopy, for several conditions. The measured threshold energy of the probe laser using a plano-convex lens with a focal length of 200 mm was 150 mJ for a xenon mass flow rate of 20 μgs and incident microwave power of 6 W; the probe laser energy was therefore set as 80 mJ. Electron number density was found to be (6.2 ± 0.4) × 10 17 m -3 and electron temperature was found to be 2.2 ± 0.4 eV at a xenon mass flow rate of 20 μgs and incident microwave power of 6 W. The threshold of the probe laser intensity against photo-ionization in a miniature xenon ion thruster is almost constant for various mass flow rates, since the ratio of population of the metastable atoms to the electron number density is little changed. © 2012 American Institute of Physics.

DOI： 10.1063/1.4737144

Language：Japanese  

Development of a Numerical Simulation Code for Microwave Discharge Ion Thrusters

DOI： 10.14822/kjsass.59.691_238

Language：Japanese  

Development or 3cm and 5cm size microwave discharge ion thrusters

Language：Japanese  

5. Study on Laser Fusion Plasma Propulsion(<Special Topic Article>New Trend of Sciences with High Energy Lasers)
将来の火星などの太陽系惑星の有人宇宙探査のためには,従来にない高い比推力と大きな推力を併せ持つ宇宙推進システム(ロケット)を開発する必要がある.その候補の一つとして,莫大なエネルギーを生成するレーザー核融合と磁気スラストチャンバーを組み合わせたレーザー核融合ロケットが挙げられる.本章では,大阪大学レーザーエネルギー学研究センターの共同利用研究施設にて実施した磁気スラストチャンバーの原理実証実験について解説する.

Language：English  

In order to improve the thrust performance of a miniature microwave discharge ion thruster, the relationship between electron number density/temperature and operational conditions, mass flow rate, incident microwave power and magnetic field strength were measured by means of laser Thomson scattering. A photon counting method and a triple grating spectrometer were used against a small Thomson scattering signal and a strong stray laser light. Electron number density increased with incident microwave power and was saturated at critical incident microwave power; it was about 1.2 x 10(18) m(-3) at incident microwave power > 8 W. In addition, electron number density increased with mass flow rate and became saturated; it was about 1.7 x 10(18) m(-3) at mass flow rate > 0.04 mg s(-1). The electron number density gradually increased with an increase in the number of magnets, i.e. magnetic field strength. There was a sudden jump at thirteen magnets, although the thruster failed to ignite at fourteen magnets. This is because there is an optimum distance between the antenna and the electron cyclotron resonance layer. These results suggest that future improvement in thrust efficiency in miniature microwave discharge ion thrusters may come from the fine adjustment of the magnetic field configuration inside the discharge chamber.

DOI： 10.1088/0963-0252/19/4/045009

Language：Japanese  

Development of 2-5cm Size Microwave Discharge Ion Thrusters

Language：Others  

Development of a cavity ring-down spectroscopy sensor for boron nitride sputter erosion in Hall thrusters
Sputter erosion of boron nitride (BN) is a critically important process in<br />
Hall thrusters from the point of view of both lifetime assessment and<br />
contamination effects. This contribution describes the development of a laser<br />
based sensor for in situ monitoring of sputtered BN from Hall thrusters. We<br />
present a continuous-wave cavity ring-down spectroscopy (cw-CRDS) system and<br />
its demonstrative measurement results from BN sputtering experiments.

Language：English  

DOI： 10.2514/1.39145

Language：Japanese  

Plasma Property Measurement in a Miniature Microwave Discharge Ion Thruster by Laser Thomson Scattering
The plasma parameters, electron number density and electron energy distribution function, in a miniature microwave discharge ion thruster were successfully measured by means of laser Thomson scattering without perturbations. A photon counting method and a double monochromator were used against small Thomson scattering signal and strong stray laser light. The result shows an electron energy distribution function is Maxwellian, since the scattered spectrum can be fitted by Gaussian at the temperature of 1.5 eV. An electron density is 2.3×10^<18> m^<-3>. The measured electron number density an...

Language：English  

We report the development of a sputter erosion monitoring system to study Hall thruster lifetime and contamination. The laser-based sensor uses the continuous-wave cavity ring-down spectroscopy technique and allows for in situ measurements in near-real time. The continuous-wave cavity ring-down spectroscopy technique diagnostic allows direct probing of sputter products in their ground state, thereby providing a reliable quantitative measure of their overall number density. Combining the number density of sputtered particles with their velocity allows determination of the flux of sputtered particles and erosion rate. We perform proof of principle experiments, in which sputtered manganese atoms from the acceleration channel of an anode layer-type Hall thruster are measured. The measurement strategy is to detect the manganese atoms via an absorption line from the ground state at a wavelength of 403.076 nm (air). The measured path-integrated number density of sputtered manganese atoms is 1.7 +/- 0.3 x 10(13) m(-2) for an argon anode mass flow rate of 2.08 mg/s and a discharge voltage of 250 V. A finite element sputter model is used to compare the cavity ring-down spectroscopy results against validating mass loss measurements and shows good agreement.

DOI： 10.2514/1.44784

Language：English  

We report the development of a sputter erosion monitoring system to study Hall thruster lifetime and contamination. The laser-based sensor uses the continuous-wave cavity ring-down spectroscopy technique and allows for in situ measurements in near-real time. The continuous-wave cavity ring-down spectroscopy technique diagnostic allows direct probing of sputter products in their ground state, thereby providing a reliable quantitative measure of their overall number density. Combining the number density of sputtered particles with their velocity allows determination of the flux of sputtered particles and erosion rate. We perform proof of principle experiments, in which sputtered manganese atoms from the acceleration channel of an anode layer-type Hall thruster are measured. The measurement strategy is to detect the manganese atoms via an absorption line from the ground state at a wavelength of 403.076 nm (air). The measured path-integrated number density of sputtered manganese atoms is 1.7 +/- 0.3 x 10(13) m(-2) for an argon anode mass flow rate of 2.08 mg/s and a discharge voltage of 250 V. A finite element sputter model is used to compare the cavity ring-down spectroscopy results against validating mass loss measurements and shows good agreement.

DOI： 10.2514/1.44784

Language：Japanese  

Effects of magnet field strength on the electron average energy inside a microwave discharge ion thruster

Language：English  

We demonstrate that large mode area (LMA) photonic crystal fibers (PCFs) can be used as single-mode patch-cords for 250 nm laser light. We have studied the transmission of the 250 nm output beam of a frequency-quadrupled diode laser through a triangular structure LMA PCF with 10 mu m core. We have achieved single-mode output with coupling loss of 1.8 +/- 0.6 dB and transmission loss of 1.5 +/- 0.2 dB/m. The critical bend loss radius is approximately 6 cm. The transmission loss is compared with published bulk silica measurements. Effects of optically induced damage were observed after prolonged operation and have been studied as function of laser power and time. The optical damage occurs primarily at the fiber input and can be partly ameliorated by cleaving the fiber input. For input power levels of <similar to 0.3 mW stable operation can be achieved for periods of >40 hours which is sufficient for many laboratory based applications. The results show the utility of these fibers for single-mode beam delivery in a spectral region where step-index single-mode fibers are not readily available. (C) 2009 Optical Society of America

DOI： 10.1364/OE.17.016933

Language：English  

We demonstrate that large mode area (LMA) photonic crystal fibers (PCFs) can be used as single-mode patch-cords for 250 nm laser light. We have studied the transmission of the 250 nm output beam of a frequency-quadrupled diode laser through a triangular structure LMA PCF with 10 mu m core. We have achieved single-mode output with coupling loss of 1.8 +/- 0.6 dB and transmission loss of 1.5 +/- 0.2 dB/m. The critical bend loss radius is approximately 6 cm. The transmission loss is compared with published bulk silica measurements. Effects of optically induced damage were observed after prolonged operation and have been studied as function of laser power and time. The optical damage occurs primarily at the fiber input and can be partly ameliorated by cleaving the fiber input. For input power levels of <similar to 0.3 mW stable operation can be achieved for periods of >40 hours which is sufficient for many laboratory based applications. The results show the utility of these fibers for single-mode beam delivery in a spectral region where step-index single-mode fibers are not readily available. (C) 2009 Optical Society of America

DOI： 10.1364/OE.17.016933

Language：English  

This contribution reports on the development of in situ sputter monitoring and end-point detection for ion beam etch systems using continuous-wave cavity ring-down spectroscopy (cw-CRDS). The demonstrated system is based on the detection of sputtered manganese atoms using a tunable external cavity diode laser in the vicinity of 403.07 nm. The cw-CRDS system is described and measurements from a manganese-iron target are presented. End-point detection is demonstrated by monitoring the time dependence of manganese concentration for a multilayer target comprised of alternating layers of manganese/iron and titanium. Detection limits are shown to be adequate for today's commercial ion beam sputter systems.

DOI： 10.1063/1.2995765

Language：Japanese  

Dependence of Thruster Configuration on Thrust Performance in Miniature Ion Thruster
The effects of antenna shape and magnetic field configuration on thrust performance in a 30W class miniature microwave discharge ion thruster were investigated with the objective of improving its thrust performance. The ion beam currents were measured for three different antenna configurations: disc, star, and cross. The results showed that the optimum antenna shape depends on the desired mass flow level because of the tradeoff between microwave-plasma coupling efficiency and surface area recombination. The ion beam current with various magnitude of magnetic field was measured, since magnet...

DOI： 10.2322/jjsass.56.383

Language：English  

The effects of magnetic field configuration on thrust performance in a miniature microwave discharge ion thruster were investigated in order to improve thrust performance. First, the extracted ion beam current was measured for various levels of strength of the magnetic field. It was found that there is an optimum magnitude of the magnetic field. That this is due to the tradeoff between magnetic mirror confinement and microwave-plasma coupling was confirmed by measurement of the ion saturation current into the antenna of the ion thruster. The ion saturation current was found to decrease with an increase in magnetic field strength, due to the improvement in magnetic mirror confinement. The estimated electron temperature also decreases with an increase in magnetic field strength. This result shows that the increase in magnetic field strength leads to a decrease in microwave-plasma coupling. Next, the ion beam current for three magnetic field shapes was measured by changing the length of the central yoke. The results show that the optimum magnetic field shape depends on the mass flow rate because of the tradeoff between magnetic confinement and ionization probability. For the configurations tested, the 3 mm length central yoke is optimal for low mass flow, whereas 7 mm is the best for high mass flow. Overall, the extracted ion beam current is 21.4 mA, at a xenon mass flow rate of 0.036 mg/s, beam voltage of 1500 V, and incident microwave power of 16 W. (c) 2007 American Institute of Physics.

DOI： 10.1063/1.2822456

Language：Japanese  

A study of energy balance in a radio frequency thruster
An energy balance in inductively coupled radio frequency electrothermal thruster using water as a propellant was investigated with the objective of improving the thrust performance. Absorption efficiency was estimated by means of an I-V sensor, enthalpy transfer efficiency was estimated by means of a spectrometer and thrust efficiency was estimated by means of a thrust stand. The absorption efficiency using water is 0.75, which is worse than that using argon. This is because the number density using water is less than that of argon due to the low ionization coefficient. The enthalpy transfe...

DOI： 10.15017/14573

Language：Japanese  

Improvement of Microwave Discharge Ion Thruster Using Antennas for Uniform and Dense Plasma Production
The dependency of thrust performance on thruster configurations such as antenna length, antenna height, number of antenna, magnetic field configuration, and microwave frequency, was investigated with the objective of improving the thrust performance of microwave discharge ion thruster using antennas for uniform and dense plasma production. The experimental results showed that there was an optimum length of the antennas, and it was 3/4 times the wave length of incident microwaves. The ion beam current reaches its maximum value when the antenna was set at 2mm downstream of an electron cyclotron resonance layer. There was an optimum number of the antennas. This is due to the tradeoff between the coupling of plasma with microwave and the surface recombination on the antenna. The expansion of ionization zone was made successfully by changing magnetic field configuration. In addition, the thrust performance was slightly improved with increase in incident microwave frequency from 2.45GHz to 4.2GHz. A value for the ion beam current with 2.45GHz is compensated by high electron number density and less magnetized ions for the disadvantage of small plasma number density. Overall, the propellant utilization efficiency, ion production cost, and estimated thrust were found to be 0.62, 300W/A and 6.2mN, respectively at mass flow rate of 0.22mg/s for xenon, ion beam voltage of 1,500V and 2.45GHz microwave incident power at 32W.

DOI： 10.2322/jjsass.55.546

Language：Japanese  

Improvement of Microwave Discharge Ion Thruster Using Antennas for Uniform and Dense Plasma Production
The dependency of thrust performance on thruster configurations such as antenna length, antenna height, number of antenna, magnetic field configuration, and microwave frequency, was investigated with the objective of improving the thrust performance of microwave discharge ion thruster using antennas for uniform and dense plasma production. The experimental results showed that there was an optimum length of the antennas, and it was 3/4 times the wave length of incident microwaves. The ion beam current reaches its maximum value when the antenna was set at 2mm downstream of an electron cyclotron resonance layer. There was an optimum number of the antennas. This is due to the tradeoff between the coupling of plasma with microwave and the surface recombination on the antenna. The expansion of ionization zone was made successfully by changing magnetic field configuration. In addition, the thrust performance was slightly improved with increase in incident microwave frequency from 2.45GHz to 4.2GHz. A value for the ion beam current with 2.45GHz is compensated by high electron number density and less magnetized ions for the disadvantage of small plasma number density. Overall, the propellant utilization efficiency, ion production cost, and estimated thrust were found to be 0.62, 300W/A and 6.2mN, respectively at mass flow rate of 0.22mg/s for xenon, ion beam voltage of 1,500V and 2.45GHz microwave incident power at 32W.

DOI： 10.2322/jjsass.55.546

Language：Japanese  

A study of energy balance in a radio frequency thruster

Language：English  

Several types of electric propulsions have been developed and used for artificial satellites on geostationary orbit keeping or planetary exploration. A series of small-scale satellites is recently expected to be used instead of traditional large-scale satellites for reducing launch cost and risk. The trend towards needs of small spacecraft requires micro thrusters with high specific impulse. In this study, a micro ion engine utilizing a microwave discharge plasma was fabricated and was tested. This ion engine comprises some components, such as electrostatic grids, antenna, and microwave power supply, which decide its performance. The performance dependence on the components was examined under several experimental conditions. The typical performance parameters of the engine were ion production cost of 770 V, propellant utilization efficiency of 72&#37;, and thrust of 0.66 mN in conditions of input 2.45 GHz microwave power of 8 W and propellant (xenon gas) flow rate of 0.2 sccm with a star type antenna. (c) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.vacuum.2006.01.071

Language：English  

In the MUCES-C mission conducted by JAXA (Japan Acro Exploration Agency), a microwave neutralizer is mounted with a microwave ion engine on the HAYABUSA space probe. The neutralizer consists of an L-shaped antenna to inject microwaves and samarium cobalt magnets to provide ECR (electron cyclotron resonance). Plasma production of a higher density than the cutoff density is expected in the discharge chamber, but the neutralizer is so small that high-precision measurements using a probe are difficult. To clarify the plasma production mechanism in the microwave neutralizer, numerical analysis was conducted using a code coupling PIC (particle-in-cell) method, and a FDTD (finite-difference-time-domain) method. This paper describes effects caused by varying magnetic field configuration and antenna position in the neutralizer. The calculation results show that bringing the antenna closer to the ECR region is effective for plasma production.

DOI： 10.2322/tjsass.49.87

Language：English  

DOI： 10.2514/1.18833

Language：English  

A small-scale ion thruster of 18 mm in diameter for space propulsion has been developed and tested. Microwave discharge plasma is produced by a star-type antenna. Two tests were carried out. First, in order to optimize the ion source configuration, we measured the ion saturation current on various conditions measured for the indicator of the performance of an ion source. Next, to estimate the thrust, the ion beam was extracted and extracted ion beam current was measured with obtained optimization configuration. The maximum ion saturation current of 45 mA was obtained at At gas flow rate of 1.4 seem and input microwave power of 28 W. The maximum extracted ion current of 22 mA was obtained at Xe gas flow rate of 0.6 seem and input power of 18 W. (c) 2006 Published by Elsevier B.V.

DOI： 10.1016/j.tsf.2005.08.045

Language：English  

Language：Japanese  

Language：English  

Results of controlling a discharge current oscillation in Hall thrusters at a frequency range of 10-100 kHz are presented. To understand the discharge current oscillation mechanism, the plasma behavior in the acceleration channel was observed with a high-speed camera using a 1-kW class, anode layer type Hall thruster. The emission intensity oscillates equably in the acceleration channel at the same period of the discharge current oscillation; the number density of excited xenon ions oscillates at the same oscillation period and is proportional to the discharge current. These results indicate that the discharge current oscillation is caused by the ionization instability and the number density of plasma oscillates equably in the acceleration channel. Furthermore, the oscillation amplitude was sensitive to the applied magnetic flux density, indicating that this oscillation is affected by electron mobility. The proposed oscillation model based on the experimental results demonstrated that the momentum transfer corresponding to a plasma fluctuation is crucial to achieving stability. Thus, the oscillation amplitude for various acceleration channel configurations-parallel and convergent-was measured, because channel configuration could affect the momentum transfer. The oscillation was successfully suppressed by adopting the convergent configuration, as shown by this model.

DOI： 10.2322/tjsass.48.169

Language：Japanese  

Performance Test of Small-Scale Microwave Discharge Type Ion Engine of 30W

Language：English  

The discharge current oscillation at a frequency range of 10-100 kHz in Hall thrusters was investigated with the objective of extending their stable operational range. The amplitude of oscillation was measured using two types of Hall thrusters-the anode layer type and the magnetic layer type. The oscillation amplitude was found to be sensitive to the applied magnetic flux density, and this result indicated that the oscillation was affected by electron mobility. An oscillation model was proposed based on the experimental results, and the predicted frequency and stable operational range were found to agree qualitatively agreed with the experimental results. This model shows that the momentum transfer corresponding to plasma fluctuation, that is, the viscosity effect, is crucial to achieving stability. Thus, the oscillation amplitude for various acceleration channel configurations-divergent, parallel, and convergent-was measured because the momentum transfer could be affected by the channel configuration. The stable operational range was successfully extended by the adoption of the convergent configuration in each type of Hall thruster, as shown by this model.

DOI： 10.2514/1.12759

Language：English  

The erosion rate of a Hall thruster was estimated with the objective of building a real-time erosion rate monitoring system using a 1 kW class anode layer type Hall thruster. This system aids the understanding of the tradeoff between lifetime and performance. To estimate the flux of the sputtered wall material, the number density of the sputtered iron was measured by laser absorption spectroscopy using an absorption line from ground atomic iron at 371.9935 nm. An ultravioletAl(x)In(y)Ga((1-x-y))N diode laser was used as the probe. The estimated number density of iron was 1.1x10(16) m(-3), which is reasonable when compared with that measured by duration erosion tests. The relation between estimated erosion rate and magnetic flux density also agreed with that measured by duration erosion tests. (c) 2005 American Institute of Physics.

DOI： 10.1063/1.2001630

Language：Japanese  

ホール型イオン源プルーム中の酸素原子密度計測

Language：Japanese  

Experimental Investigation of a Hall Thruster Using Oxygen as the Propellant
Thrust performance and internal efficiencies of a Hall thruster using oxygen as the propellant were investigated experimentally. The thrust efficiency reached at 9&#37; with the specific impulse of 1,000s. The relatively poor performance is due to low propellant utilization, which is 45&#37;, in comparison with that in the case of xenon propellant. The propellant utilization increased with mass flow rate and discharge voltage. The optimum channel length for oxygen was found longer than that for xenon, which was 12mm. The use of BN・AlN for the channel wall results in higher propellant utilization th...

DOI： 10.2322/jjsass.51.606

Language：Japanese  

Operating Charaeteristics of an Anode Layer Tyne Hall Thruster
Thrust performance and stable operation conditions of an anode layer type Hall thruster was investigated using a 1.5kW class anode layer type Hall thruster. The thrust efficiency reached at 53&#37; with the specific impulse of 2,000s, which are competitive with these of SPT-100 thrusters. Anode shape and axial position of the anode were changed. Stability of the discharge was found sensitive to the anode configuration and applied magnetic flux density.

DOI： 10.2322/jjsass.51.492

Language：Japanese  

作動ガスに酸素を用いたホール加速器のイオンビーム特性

Language：English  

Characteristics of plasma fluctuations at the frequencies 10-100 kHz in Hall thrusters were investigated since the fluctuations might affect not only its performance but also its lifetime. Measured fluctuation characteristics varied with magnetic flux density of the applied field and they were categorized into the four regimes. Since the electron mobility strongly depends on applied field strength, it was thought that electrons would play an important role on this oscillation. Therefore, the oscillation model derived from ionization instability considering electron mobility was proposed. The predicted stable/unstable operating condition map agreed well with the measured one. (C) 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0042-207X(01)00445-6

Language：Japanese  

ホール加速器における放電振動と推進性能の関係

Language：Japanese  

ホール型推進機の放電振動

Type：Competition, symposium, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：6

Number of peer-reviewed articles in Japanese journals：6

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Number of participants：1,000

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Number of participants：823

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Number of participants：823

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Number of participants：1,600

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