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

DOI： 10.1585/pfr.18.2402084

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

DOI： 10.1088/1741-4326/acee13

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

DOI： 10.1585/pfr.18.2402066

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

DOI： 10.1088/1741-4326/acd4d1

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

DOI： 10.1016/j.fusengdes.2023.113794

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

DOI： 10.1585/pfr.18.1305048

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

DOI： 10.1016/j.fusengdes.2023.113648

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

DOI： 10.1585/pfr.18.2405035

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

DOI： doi.org/10.1016/j.fusengdes.2023.113479

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

DOI： doi.org/10.1585/pfr.18.2403019

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

DOI： doi.org/10.1585/pfr.18.1405012

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

DOI： 10.1088/2058-6272/acafc2

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

DOI： 10.1109/TPS.2022.3193069

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

DOI： doi.org/10.1007/s10894-022-00338-4

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

DOI： doi.org/10.1063/5.0101770

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

DOI： 10.1063/5.0101632

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

DOI： 10.1016/j.fusengdes.2022.113199

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

An upgraded Ohmic heating (OH) system with a bipolar circuit is designed to achieve plasma current over 100 kA ideally without the effect of eddy current in the QUEST spherical tokamak. IGBT (Insulated Gate Bipolar Transistor) stacks work as switches to change the polarity of OH primary current up to ±8 kA. A main target of the new OH is to generate over-dense plasmas for the 8.56 GHz electron cyclotron (EC) wave. Heating with electron Bernstein waves can be conducted in such over-dense plasmas. The effect of eddy current flowing in the vacuum vessel, which is generated by the current swing through the central solenoid, on null point is investigated by analysis of magnetic field and flux surfaces. In the initial phase, eddy current flowing through the vacuum chamber shifts the null point to the high magnetic field side where multiple EC resonance layers are located.

DOI： 10.1016/j.fusengdes.2021.112362

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

QUEST (Q-shu university experiment with steady state spherical tokamak) is a midsize spherical tokamak capable of steady-state operation, comprising all-metal plasma-facing walls and a hot wall (HW) to address issues pertaining to fuel particle balance. The HW was installed summer 2014. Quantitative analysis pertaining to the HW at 373 K is carried out, and clarify the quantitative impact of shot history that obviously appears in wall stored hydrogen just before the discharge at the wall temperature. The model indicates the plasma-induced deposition layer play an essential role in fuel particle balance. A clear temperature dependence of fuel recycling was observed using outgassing just after plasma termination and played an essential role in regulation of particle balance. Consequently, long duration discharges lasting more than 1 h has been obtained at wall temperature, TW < 423 K in the range of 40–60 kW of RF power and, similarly, a 6 h discharge could be achieved at TW = 473 K using 20 kW of injected RF power.

DOI： 10.1016/j.nme.2021.101013

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

In the GAMMA 10/PDX tandem mirror, plasma with strong ion-temperature anisotropy is produced by using the ion cyclotron range of frequency waves. This anisotropy of ion temperature causes several Alfvén-Ion-Cyclotron (AIC) waves to spontaneously excite in the frequency range just below the ion cyclotron frequency. In addition, difference-frequency (DF) waves are excited in the radial inner region of the plasma by wave-wave coupling among the AIC waves. The radial density profiles were measured at multi-axial positions using a frequency-modulation reflectometer with an axial array of microwave antennas, and an axial variation of the density was found to be significant. In addition, a relative phase difference of the DF wave between axially separated two points was first obtained by finely choosing the probing frequency of the reflectometers with a maximum coherence used as a measure, indicating that the DF wave is a propagating wave, while the pump AIC waves are standing waves in the axial region of measurement.

DOI： 10.1063/5.0043821

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

A spectroscopic system with multiple viewing chords was developed for QUEST (Q-shu University Experiment with Steady-State Spherical Tokamak) to measure the spatial distribution of ion toroidal velocities in discharges sustained by electron cyclotron resonance heating (ECH). Twenty-four viewing chords were aligned in the midplane and C III emission line spectra were measured for three types of ECH discharge under different magnetic field configurations. By applying an inversion method to the measured spectra, we evaluated the radial distributions of C2+ ion emissivity, temperature, and toroidal velocity. The error in the evaluated velocity was estimated to be less than 5 km/s. It was found that the velocity depends on the magnetic field configuration.

DOI： 10.1016/j.nme.2021.100905

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

DOI： doi.org/10.1585/pfr.16.2402034

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

To study radial distribution of hydrogen flux in peripheral plasma in long duration tokamak discharges, permeation and Langmuir reciprocate probes are used. The atomic hydrogen flux to the walls at several radial positions is deduced from the permeation flux. Contribution of the ions to the hydrogen flow is deduced from the Langmuir probe ion saturation current. It is found, that the atomic hydrogen has the most contribution to the hydrogen flow behind the plasma facing components (PFCs), while the ion flux there is negligible. The atomic flux behind the PFCs drops to the value of F~4.3×1015H/m2/s, which is ~6 % of that just in front of PFCs, F~7.7×1016H/m2/s.

DOI： 10.1016/j.nme.2020.100872

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

DOI： 10.1585/pfr.16.2402045

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

The plasma current is ramped up primarily by a 28 GHz electron cyclotron wave (ECW) in the Q-shu University experiment Steady-State Spherical Tokamak (QUEST), with multiple harmonic resonance layers from the second to the fourth stay in the plasma core. A steering antenna comprising two quasi-optical mirrors enhances the power density of ECWs. The ECW beam is injected obliquely from the low-field side where the parallel refractive index is N ∥ = 0.75 at the second-harmonic resonance layer. Analysis of the resonance condition has found that energetic electrons moving forward along the magnetic field resonate more effectively than those moving backward. Such symmetry breaking is consistent with the results of the current ramp-up experiment. The peak plasma current reaches I p > 70 kA, constantly injecting a beam of radio frequency power of 100 kW. Ray-tracing by the TASK/WR code demonstrates that the power of the 28 GHz extraordinary mode is absorbed by energetic electrons via single-pass cyclotron absorption.

DOI： 10.1063/5.0031357

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

The spatial distribution of the hydrogen atom density was evaluated in a spherical tokamak (ST) plasma sustained only with 28 GHz electron cyclotron heating (ECH). The radially resolved Hδ emissivity was measured using multiple viewing chord spectroscopy and Abel inversion. A collisional-radiative (CR) model analysis of the emissivity resulted in a ground-state hydrogen atom density of 1015-1016 m-3 and an ionization degree of 1-0.85 in the plasma.

DOI： 10.3390/ATOMS8030044

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

As technology has improved in recent years, it has become possible to create new valuable functions by combining various devices and sensors in a network. This concept is referred to as the Internet of Things (IoT), and predictive maintenance is a new valuable function associated with the IoT. In large-scale experimental facilities with many researchers, it is not desirable that experiments cannot be performed due to sudden failure of equipment. For this reason, it is important to predict the failure in advance based on the measurement results of sensors and to perform repairs in a planned manner. On the Q-shu University experiment with steady-state spherical tokamak (QUEST) large experimental device, it is necessary to drive a large current of 50 kA, and the diagnosis of its power line deterioration is well performed as predictive maintenance through the evaluation of its contact resistances of several micro ohms order on the network. In addition, as an example of the IoT, mechanisms to assist safe operation, such as a sound alarm system and an entrance management system, are built by sharing experimental information between devices via the network.

DOI： 10.1016/j.heliyon.2020.e04214

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

This paper presents a detailed design of the Q-shu University experimental steady state spherical tokamak's (QUEST's) high-field side (HFS) injection system for electron Bernstein wave (EBW) excitation and the results of an experimental comparison of the HFS eXtraordinary X-mode and low-field side (LFS) ordinary O-mode injection of 8.2 GHz radio frequency (RF) power. Waveguides, as an alternative to mirror polarizers for transmitting RF X-mode power from LFS to HFS for EBW conversion, were used instead of the installation of an RF mirror. Testing of LFS-to-HFS RF power transmission at 8.2 GHz, using an RG-50-type vacuum waveguide in a bench-scale device filled with SF₆ gas at 0.03 Mpa, revealed that an RF power of 10.8 kW could traverse the fundamental electron cyclotron resonance layer for 60 s without breakdown. The short-length, open-ended waveguide antenna used in the HFS injection-induced wave diffraction reduced the efficiency of power delivery to the upper hybrid resonance (UHR) by approximately 7% at an electron temperature of 50 eV. The HFS injection was able to produce brighter camera images than the standard LFS injection. The location of the UHR, as estimated by measuring the density with an interferometer, agreed with its location as measured by plasma radiation low-field, side-edge positions shown by fast camera imaging. This indicates that the plasma was produced by mode-converted EBW. The HFS injection had an absorption efficiency of 96%, compared to 40% for LFS. A greater fluctuation of floating potential adjustable to the lower hybrid wave (LHW) was observed in the HFS case by installing a Langmuir probe, confirming that EBW conversion efficiency was higher in the HFS case. Moreover, after setting the poloidal field to B_PF = 7.6 mT, plasma current (I_P ) in the HFS peaked at 1.3 kA, as opposed to 0.3 kA for LFS, despite LFS injection having a total power of 55 kW, compared to 40 kW for HFS. However, as the impurity level was comparatively high, it is believed that this I_P is dominated by pressure-drive, which makes it difficult to analyze EBWCD. Finally, the line-integrated density in the HFS injection peaked at 1.6 × 10¹⁸ m^-2, compared to 8 × 10¹⁷ m^-2 in the LFS one.

DOI： 10.1088/1361-6587/ab6903

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

A 28 GHz system with a high-power gyrotron tube has been used for the QUEST spherical tokamak to form an over-dense plasma for electron Bernstein wave (EBW) heating and current drive with an 8.2 GHz-wave. Non-inductive high-density plasma ramp-up experiments with dual-frequency (dual-f ) electron cyclotron (EC) (8.2 GHz and 28 GHz) waves were conducted. A spontaneous density jump (SDJ) to an over-dense state was first observed as a bifurcation phenomenon in the dual-f  wave experiment. The over-dense plasma on the 8.2 GHz wave was non-inductively ramped up to 25 kA, and was maintained for 0.4 s under stable plasma equilibrium after two such jumps in one shot. Heating to mildly energetic electrons and bulk electrons was observed even in the over-dense region. The electrostatic EBW heating effect on the mildly energetic electrons in the over-dense region is assessed following a dispersion analysis of the 8.2 GHz wave. The bulk electron heating effect observed is explained as heat exchange from mildly energetic electrons heated by the electrostatic EBW. Remarkably, a high hard-x-ray-radiation temperature of  ~500 keV was also observed in tangential viewing for current-carrying electrons in the over-dense core region. Synergetic heating from the overlap of different 28 GHz EC harmonic resonances as well as higher harmonic heating is discussed for maintaining the highly energetic electrons in the over-dense core region. In addition, the SDJ process and mechanism are considered based on the discussion of the electron heating effects with the 8.2 GHz wave.

DOI： 10.1088/1741-4326/ab4c12

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

A high voltage DC power supply for the cathode of the 8.56 GHz CW klystron has been set up for electron cyclotron heating (ECH) in steady state tokamak operation on QUEST spherical tokamak. The power supply is equipped with an IGBT array and a reactor for fast shutoff of the voltage in 10 μs, where the influx of electric energy at the short circuit is limited to 5 J. AC switches also have been installed in the three-phase power lines. High voltage relays are useful to save electric energy consumption. Fast three-phase AC switching by IGBT-stack is applicable to reduce the electric load of the components of the klystron power supply.

DOI： 10.1016/j.fusengdes.2019.04.043

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

A launcher system for a round-trip interferometer, with a corrugated horn antenna and two quasi-optical mirrors, has been developed for the QUEST spherical tokamak experiment. The corrugated horn antenna has been designed using a three-dimensional (3D) electromagnetic simulator. At low power bench test, intensity and phase profiles at 0.1 m from antenna aperture show coaxial patterns as predicted by the 3D simulator, in agreement with the calculation results using an in-house developed Kirchhoff integral code. The designed waist sizes of the focused beam at a target position are 22mm in the horizontal x direction and 43 mm in the vertical y direction. The beam reaches the target plate at QUEST's center-post and is reflected back along the line-of-sight round-trip. A well-focused beam of 32 and 36 mm in size (x, y) has been obtained at the target position. The HE11 mode excitation, beam transmission, and focusing properties are discussed for the prototype launcher system.

DOI： 10.1585/PFR.14.3402122

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

A two-dimensional (2D) phased-array-antenna (PAA) for electron cyclotron emission is one of the diagnostics for finding the window area of mode conversion from electron cyclotron waves to electron Bernstein wave. Spatial resolution of the reconstructed emission field pattern is improved with a lot of the antenna elements. The study proposes a phased-array patch loop antenna (PAPA) as a promising system to increase the elements of PAA. A 2D image reconstruction of a 6 GHz radio frequency source emission shows that the source position is detected within millimeter range by applying the prototype PAPA. This result indicates that the 2D image reconstruction with multi-element PAPA is feasible.

DOI： 10.1585/PFR.14.3402111

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

In the hot ion mode experiments of the tandem mirror GAMMA 10/PDX plasma, suppression of the flute-like fluctuation, for which the rotation direction is the same as the ion diamagnetic rotation direction, was observed during the axially confined potential formation while electron cyclotron heating (ECH) was applied at the barrier and plug cells for the first time. In the previous experiments, the electron diamagnetic rotation type fluctuations were clearly suppressed with the application of both barrier (B) and plug (P) ECH. We show that the flute-like fluctuation of ion diamagnetic rotation is also suppressed with the application of P/B-ECH.

DOI： 10.1088/1741-4326/ab160d

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

We have investigated the synergistic effect of a combination of various impurity gases and hydrogen gas on plasma detachment of high temperature plasma, equivalent to scrape-off layer plasma of tokamaks in the GAMMA 10/PDX end region, utilizing an open magnetic field configuration. A small puff of an impurity gas (N₂, Ne, Ar, Kr, Xe) in combination with a puff of H₂ gas is examined to evaluate their synergistic effect on the formation of detached plasma; the following results are obtained. (i) A combination of N₂ and H₂ puffs showed a clear decrease of electron density and ion flux; (ii) N₂ and H₂ puffs form a strong density gradient along the axial direction; and (iii) other noble impurity gases showed an insufficient synergistic effect. The new results indicate the possibility of achieving a reliable divertor operation scheme and the importance of a deeper understanding of the H₂ and N₂ assisted recombination process.

DOI： 10.1088/1741-4326/ab1a4a

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

A new transmission line from 28 GHz gyrotron to QUEST spherical tokamak (ST) has been developed for the highly efficient electron cyclotron heating and current drive (ECHCD) experiments. The ECHCD effect depends on the incident mode or polarization states of the injected beam. Although two corrugated-polarizer miter bends were developed and assembled to transmission line in the QUEST, arcing events were frequently detected at the polarizer miter bend when the high-power millimeter-wave were transmitted. A new quasi-optical (QO) concept for the polarizer system composed of two corrugated plate and a QO mirror was proposed to avoid the arcing at polarizer. The QO mirror was designed for coupling of input and output HE
₁₁
modes at the polarizer, its coupling property is discussed with Kirchhoff integral. Polarization-setting performance of the developed QO polarizer was examined in a low-power test system, and is discussed with grating-polarizer calculation.

DOI： 10.1016/j.fusengdes.2019.02.099

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

Ion cyclotron emission (ICE) is probably excited by non-thermal ion velocity distribution. Identifying characteristics of the ion velocity distribution that excites the ICE can contribute to understanding its emission mechanism. The characteristics of fast helium-3 (³He) ion velocity distribution that excites ³He ICE [ICE(³He)] on JT-60U are investigated. First, fast deuterium ion distributions, which mainly contribute to deuterium-deuterium fusion reactions, are calculated with a fast ion orbit following Monte-Carlo code (OFMC code) under realistic conditions to evaluate birth spatial and velocity distributions of the ³He ions. Then, the fast ³He ion distributions are evaluated with the OFMC code using the birth distributions and compared between cases when the ICE(³He) is observed and not. The evaluated fast ³He ion distributions at the midplane edge of the plasma on the low field side have strong pitch-angle anisotropy in both cases. In the case with the ICE(³He) excitation, a relatively peaked bump-on tail structure in the energy direction is formed in the distributions. The formation of the relatively peaked bump-on tail structure is localized at the plasma edge on the low field side. On the other hand, the distributions at the plasma edge on the low field side have a broader structure in the energy direction in the case without the excitation. The comparison results show that the formation of the relatively peaked bump-on tail structure in the fast ³He ion distribution makes a key contribution to the excitation of the ICE(³He) on JT-60U.

DOI： 10.1088/1361-6587/aaf184

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

We used the additional Ion Cyclotron Range of Frequency (ICRF) heating in the anchor cell for the high density plasma production. When the ICRF waves are excited with antennas installed in the anchor cell, it is observed that the plasma potential increases significantly and forms non-axisymmetric potential distribution in the periphery of the central cell. Experiments with different frequencies were carried out to understand the physical mechanism of this potential change due to the ICRF waves. It is confirmed that the ion heating does not play an important role to the potential increase. The floating potentials on some tips set outside of the plasma in the anchor cell remarkably decrease during the additional heating and non-axisymmetric distribution of the floating potential in the central cell depends on the antenna location in the anchor cell. It is suggested that the radial transport of electrons near the antennas in the non-axisymmetric anchor cells with the ICRF antennas is a possible candidate of the potential increase in the central cell.

DOI： 10.1585/pfr.14.2401028

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

Beach heating using a slow Alfvén wave in ion cyclotron range of frequencies would be the first candidate for ion heating in a DEMO-relevant divertor testing linear plasma device if it is applicable to a high-density regime. To clarify its availability, the density dependence of a slow wave excitation is investigated using a full wave simulation with TASK/WF3D code in the GAMMA 10/PDX central cell configuration, where there is an extensive track record of a beach heating. A shielding effect is successfully demonstrated and well understood under a three-dimensional configuration in the limit of cold plasma approximation. As the density increases, excitable left-handed electric field, which contributes to ion cyclotron heating, degrades more and more from a core region, and resultantly the ion absorption region goes outwards with reducing its power. For core densities above 10²⁰ m^-3, the wave field exists only at a very edge, and ion heating becomes negligible unless the wave frequency is much increased with a correspondent magnetic field enhancement.

DOI： 10.1585/pfr.14.2402003

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

In the GAMMA 10/PDX tandem mirror, studies on divertor physics have been performed in the west end region by utilizing end-loss plasmas flowing from the confinement region. Since the plasma density in the end region is quite low (~ 10¹⁶ m^-3), an increase of the end-loss ion flux is required. The increase of the end-loss ion flux has been obtained by increasing the density in the confinement region on previous experiments. When an additional ICRF heating using the antennas in the anchor cells has been performed, a significant increase of the ion flux has been observed with the increase of the potential in the central cell although the change of line densities in the confinement region is little. The effect of the potential on the ion flux has been examined on the GAMMA 10/PDX using about 10,000 discharges. The ion flux increases almost linearly with the potential and the density increase. By comparing with a simple calculation, the increase of the ion flux is explained by the expansion of loss cone boundary of ions and the decrease of the transport time of the end-loss ions from the confinement region to the end region.

DOI： 10.1585/pfr.14.2402032

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

DOI： 10.1585/pfr.14.2902065

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

High field side (HFS) injection of eXtra-ordinary X-mode for electron Bernstein wave (EBW) conversion was conducted in the QUEST tokamak. Radio frequency (RF; 8.2 GHz) power was delivered from the low field side (LFS) to the high field side HFS through waveguides, and from the HFS placed 20 cm above the midplane of the vacuum vessel. The aim was to compare the RF launches from the LFS and HFS. The plasma brightness, measured by a fast camera, as well as the H
_α
signal captured along the mid-plane, was noticeably higher in the HFS launch than in the LFS launch. The HFS injection achieved a plasma current of approximately 130 A, versus 35A in the LFS injection. The electron density n
_e
predicted from the position of the upper hybrid resonance agreed with the line-averaged n
_e
measured by an interferometer, confirming the effective conversion and subsequent damping of the EBW mode. The RF leakage of the HFS injection was less than one-sixth that of the LFS injection. These results indicate that HFS delivers better RF coupling and conversion efficiency to EBW than LFS injection. Such efficient plasma heating via EBW will significantly enhance the plasma production.

DOI： 10.1585/pfr.14.1205038

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

A high voltage DC power supply for the cathode of the 8.56 GHz CW klystron has been set up for electron cyclotron heating (ECH)in steady state tokamak operation on QUEST spherical tokamak. The power supply is equipped with an IGBT array and a reactor for fast shutoff of the voltage in 10 μs, where the influx of electric energy at the short circuit is limited to 5 J. AC switches also have been installed in the three-phase power lines. High voltage relays are useful to save electric energy consumption. Fast three-phase AC switching by IGBT-stack is applicable to reduce the electric load of the components of the klystron power supply.

DOI： 10.1016/j.fusengdes.2019.04.043

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

The transition of a detached to attached plasma experiment has been performed in GAMMA 10/PDX by applying an additional plasma heating pulse of electron cyclotron heating (ECH). In a plasma detachment experiment, a short pulse (25 ms) of ECH was applied at the east plug-cell to examine the effects of electron heating on the plasma parameters in the D-module. It was found that the ion flux increased significantly during ECH injection. In the ECH injection period, the ion flux increased with the increasing impurity injection, which indicates the impurity ion components are enhanced by ionization in the D-module due to the application of ECH. During ECH injection period, the increase of the ion flux near the corner of the target plate shows a clear dependence on the gas species. The 2D visible emission has been captured by the high-speed camera and a bright emission near the corner of the target has been observed. The spectroscopic measurement in the D-module shows that the impurity ion emission increases remarkably during ECH injection. These results indicate the detached plasma change to the attached state.

DOI： 10.1016/j.nme.2018.12.033

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

To investigate end-loss plasma control, several heating operations were carried out using ion-cyclotron range of frequency (ICRF) heating systems in GAMMA 10/PDX. In anchor region, one of the important heating positions to control the end loss particle and heat fluxes, excited ICRF waves are measured as the density fluctuations using an upgraded reflectometer system and the detailed radial profiles are observed. The efficiency of anchor heating was changed using the phase control between two antennas installed in the anchor and/or the central region. The interference of two waves during a phase-control ICRF heating has been directly measured inside the plasma. In addition, several phase dependencies were observed using absorption methods with photodiode in anchor region.

DOI： 10.1585/pfr.14.2402055

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

In the west end of GAMMA 10/PDX, the end-loss ion flux is utilized for divertor simulation experiments. It is important for controlling parameters of the end-loss ion flux to investigate the efficiency of ion cyclotron range of frequency (ICRF) heating in the west plug/barrier cell, which is next to the west end region. The ICRF heating experiments in the west plug/barrier cell have been performed. In this study, three-dimensional simulations of the ICRF wave propagation were carried out in the plug/barrier cell for the first time. Two types of antennas, a Double Half Turn (WB-DHT) and a Nagoya Type-III (WB-Type-III) antennas, are evaluated. As the results, it is clarified that the WB-Type-III antenna is more effective for the ion heating than the WB-DHT antenna when the frequency is near the ion cyclotron resonance frequency at the midplane of the plug/barrier cell. An additional experiment with the WB-Type-III antenna which is located near the midplane of the plug/barrier cell has been performed. The improvement of the power absorption has been observed. TheWB-Type-III antenna located near the midplane is more effective for the ion heating. The experimental results are consistent with the simulation of the wave propagation analysis.

DOI： 10.1585/pfr.14.2401012

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

Effective ICRF heating creates a high ion-temperature plasma with strong ion-temperature anisotropy in the GAMMA 10/PDX central cell, where several Alfvén-ion-cyclotron (AIC) waves are spontaneously excited. It is clearly measured with a microwave reflectometer installed in the central cell that waves with the difference frequencies of the AIC waves are excited in a core region. In addition, it has been observed with an end-loss high-energy ion detector that high-energy ions of over 6 keV are axially transported along the magnetic field lines with the same frequencies as the difference frequencies of the AIC waves. In this study, in order to understand the related wave-particle interaction, another end-loss high-energy ion detector using a micro-channel plate has been developed. By changing the ion retarding grid voltage, which the new detector equips, it is found that an energy dependence exists in the loss mechanism; some frequencies that the axial transport includes disappear for high-energy ions of over 6 keV while they are significant for low-energy ions. In addition, by changing the radial position of the new detector, a radial localization of the axial transport to a core region, which is consistent with the profile of the difference frequencies waves, is indicated.

DOI： 10.1585/pfr.14.2402033

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

Slow Alfvén wave with a frequency just below an ion cyclotron frequency can be destabilized by the anisotropy of ion temperature and called as Alfvén-Ion-Cyclotron (AIC) wave. In the GAMMA 10/PDX central cell, several AIC waves simultaneously appear in an unstable frequency range. In addition, low-frequency waves with the difference frequencies (DF) between the AIC waves are observed, and their characteristics have to be clarified to reveal their unknown contributions to the ion transport suggested in GAMMA 10/PDX. In this study, simultaneous two-point measurements in the azimuthal and axial directions were conducted by using a two-channel microwave reflectometer with multi horn antennas. The azimuthal mode number (m) of the DF waves was confirmed at inner plasma region for the first time, and was zero, which satisfies azimuthal mode matching with the m = -1 AIC waves. In addition, it was shown that the DF waves were radially localized in an inner region, which is different from rather broad profiles of the AIC waves.

DOI： 10.1585/pfr.14.2402011

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

Establishment of fueling system is one of the critical issues for the future fusion reactors. Fueling experiment supersonic molecular beam injection (SMBI) have been carried out in the central-cell of GAMMA 10. In GAMMA 10, electron cyclotron resonance heating (ECRH) is used at plug/barrier-cells for the formation of the axial confining potential. Recently, ECRH was applied during SMBI to plug the loss particles and increased the plasma density in the central-cell compared to without ECRH. This result suggests that the particles are confined during SMBI due to the injection of ECRH at plug/barrier-cells in GAMMA 10.

DOI： 10.1088/1742-6596/959/1/012007

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

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

The Magneto-acoustic Cyclotron Instability (MCI) is a possible emission mechanism for Ion Cyclotron Emissions (ICEs). A dispersion model of the MCI driven by a drifting-ring-type ion velocity distribution has been proposed. In this study, the model was compared with the experimental observations of ³He ICEs [ICEs(³He)] on JT-60U. For this purpose, at first, velocity distributions of deuterium–deuterium fusion produced fast ³He ions at the time of an appearance of the ICE(³He) were evaluated by using a fast ion orbit following code under a realistic condition. The calculated distribution at the edge of the plasma on the midplane on the low field side is shown to have an inverted population and strong anisotropy. This distribution can be reasonably approximated by the drifting-ring-type distribution. Next, dispersions of the MCIs driven by the drifting-ring-type distribution were compared with those of observed ICEs(³He). The comparison shows that toroidal wavenumbers and frequencies of the calculated MCIs agree with those of the observed ICEs(³He).

DOI： 10.7566/JPSJ.86.124501

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

Slow Alfvén wave in ion cyclotron range of frequency (ICRF) is a powerful tool to heat ions confined in a mirror field. In spite of its efficient heating effect that has been attained in the central cell of GAMMA 10, there are still unknown characteristics concerning boundary condition, transient variation of heating effect, exact picture of cyclotron damping, and so on. To study these characteristics in detail, a multi-point measurement of the waves inside the hot plasma has been recently developed by using a microwave reflectometer. In addition to a radial profile measurement that is available by a usual reflectometer, an axial measurement has been achieved by arraying transmitting and receiving horn antennas in the axial direction, which are repeatedly switched in time during a discharge with PIN diode switches. Another transmitting and receiving horn antenna pair was newly added to the system and probing at five cross sections was achieved in a single discharge with time resolution of about 1 ms at each antenna pair position. With the upgraded reflectometer system, axial and radial distributions of wave-induced fluctuations and those temporal behavior were clearly observed, offering valuable data on wave physics in a hot mirror plasma.

DOI： 10.1088/1748-0221/12/12/C12017

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

This paper describes the recent progress in divertor simulation research using the GAMMA 10/PDX tandem mirror towards the development of divertors in fusion reactors. During a plasma flow generation experiment in the end cell of the GAMMA 10/PDX, ICRF heating in the anchor cell successfully extended the particle flux up to 3.3 10²³ m² s^-1. Superimposing the short pulse of the ECH also attained a maximum heat flux of ∼30 MW m^-2. We have succeeded in achieving and characterizing the detachment of the high-temperature plasma, which is equivalent to the SOL plasma of tokamaks, by using the divertor simulation experimental module (D-module) in the GAMMA 10/PDX end cell, in spite of using a linear device with a short magnetic field line connection length. Various gases (Ar, Xe, Ne and N₂) are examined to evaluate the effect of radiation cooling against the plasma flow at the MW m^-2 level in the divertor simulation region and the following results are obtained: (i) Xe gas was most effective in the reduction of heat and particle fluxes (1%, 3%, respectively) and has a stronger effect on electron cooling (down to ∼1.6 eV) in the used gas species. (ii) Ne gas was less effective. On the other hand, (iii) N₂ gas showed more favorable effects than Ar in the lower pressure range. These results will contribute to the progress in detached plasma operation and in clarifying the radiation cooling mechanism towards the development of future divertors.

DOI： 10.1088/1741-4326/aa7cb4

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

A two-channel microwave reflectometer system with fast microwave antenna switching capability was developed and applied to the GAMMA 10 tandem mirror device to study high-frequency small-amplitude fluctuations in a hot mirror plasma. The fast switching of the antennas is controlled using PIN diode switches, which offers the significant advantage of reducing the number of high-cost microwave components and digitizers with high bandwidths and large memory that are required to measure the spatiotemporal behavior of the high-frequency fluctuations. The use of two channels rather than one adds the important function of a simultaneous two-point measurement in either the radial direction or the direction of the antenna array to measure the phase profile of the fluctuations along with the normal amplitude profile. The density fluctuations measured using this system clearly showed the high-frequency coherent fluctuations that are associated with Alfvén-ion-cyclotron (AIC) waves in GAMMA 10. A correlation analysis applied to simultaneously measured density fluctuations showed that the phase component that was included in a reflected microwave provided both high coherence and a clear phase difference for the AIC waves, while the amplitude component showed neither significant coherence nor clear phase difference. The axial phase differences of the AIC waves measured inside the hot plasma confirmed the formation of a standing wave structure. The axial variation of the radial profiles was evaluated and a clear difference was found among the AIC waves for the first time, which would be a key to clarify the unknown boundary conditions of the AIC waves.

DOI： 10.1063/1.4978323

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

Results of supersonic molecular bean injection (SMBI) with Laval nozzle has been carried out in the GAMMA 10 tandem mirror. The neutral transport during SMBI was investigated by the two-dimensional image of the light emission captured by the high-speed camera. We used the value of full width at half maximum (FWHM) of the distribution of emission intensity as an index of neutral transport. The FWHM value decreases with the increase of the plenum pressure which indicates that the particle diffusion was more convergent at high plenum pressure. Fully three-dimensional neutral transport simulation using a Monte-Carlo code DEGAS is applied to SMBI experiment and simulation results qualitatively explained the experimental results.

DOI： 10.1063/1.4964174

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

This paper presents an overview of the recent progress of GAMMA 10/PDX project. In the GAMMA 10/PDX project, development of fusion reactor relevant research related to magnetic mirror devices has been conducted. One of the main objectives is divertor simulation studies under the similar condition of actual fusion devices, which contributes to comprehensive development strategy towards the divertor plasma physics and plasma wall interaction (PWI) studies. The recent progress of this research is that an additional plasma heating (ICRF and ECH) significantly increased the ion flux up to 3.3 × 10²³ /m² s at the end-mirror exit, which proved an effectiveness of additional plasma heating for generating high ion flux from the mirror end. Superimposing a short pulse of ECH produces the maximum heat flux of 21 MW/m² by improving the west plug ECH antenna system, which exceeds the heat-load of ITER divertor plates. In detached plasma formation experiments using the divertor simulation experimental module (D-module), comparison of various radiator gases (Xe, Ar, Ne, N₂) injected into D-module showed that Xe was the most effective gas on electron cooling and reduction of heat and ion fluxes. In the development of high-power gyrotrons, a number of electron cyclotron heating experiments using high-power gyrotrons have been performed under strong collaboration and we made a remarkable contribution to LHD and QUEST. The first 28 GHz MW tube has attained 1.38 MW and new MW-level dual frequency gyrotron test is also in progress and 1.22 MW at 28GHz is achieved. Multi-channel/multi-pass Thomson scattering system has been developed and simultaneous measurement of radially 6 points with 10 Hz can be available. The multi-pass function of this system also improved the measurement accuracy and time resolution. Microwave interferometer system has been developed in the GAMMA 10/PDX end-cell, which contributes to detailed diagnostics for divertor simulation plasmas in D-module.

DOI： 10.1063/1.4964155

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

On the GAMMA 10/PDX tandem mirror machine, divertor simulation experiments are carried out in the west end region by utilizing the particle flux from the confinement region. In order to control the particle flux and the ion temperature on the west end region, we have tried ICRF heating experiments with two types of antennas, double half turn (DHT) and Nagoya Type-III antennas, located in the west barrier cell. The ICRF heating in the barrier cell is effective for increasing the ion temperature at the end region. On the other hand, the particle flux is decreased due to the trapping of the ions from the central cell. This effect is more explicit by use of the Type-III antenna than the DHT antenna. The direct heating of the end-loss ions in the end region has been demonstrated to be effective for the increase of both ion temperature and particle flux.

DOI： 10.1063/1.4964167

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

The microwave reflectometer system in the GAMMA 10 central cell has been recently upgraded using PIN diode switches and an axial array of transmitting and receiving horn antennas to investigate internal structures of ICRF waves. The system successfully worked to measure high-frequency density fluctuations accompanied by ICRF waves at multi axial locations in a single discharge. By using several discharges for radial scan with the axial antenna switching, radial and axial measurement of the density fluctuations was achieved. Obtained profiles of 6.36 MHz ICRF wave for ion heating show axial variation in those intensity, suggesting the effect of cyclotron damping. Furthermore, in accordance with the unexplained variation of diamagnetism before the main ramp-up, the intensity near the ICRF antenna is found to also vary in time. The developed system is useful to study the behavior of ICRF waves inside a hot plasma.

DOI： 10.1063/1.4964196

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

Characteristics of axial plasma confinement in recent high-density mode of GAMMA 10/PDX tandem mirror is reported in this paper. The parameter of the end-loss ion flux is an important issue in the divertor simulation studies in GAMMA 10/PDX. With an ICRF heating in the anchor-cells of the machine, large increase in the electron line-density in the central-cell (NLCC) and the end-loss particle flux were observed. The behavior of the electron line density, plasma temperature and the amount of end-loss ion flux during the experiments suggested that the mechanism of the axial ion loss was changed due to the increase of ion collision frequency. In contrast with the standard operations of GAMMA 10/PDX, plasma parameters in recent high-density operations stays in the range of high collision frequency. In such collisional plasma, the end-loss ion particle flux show linear dependence on the plasma density instead of the parabolic dependence expected in plasmas of low collisionfrequency. In the high collision frequency plasma, it is notable that plasma potential φ largely changes the dependence of the particle flux on the plasma density.

DOI： 10.1585/pfr.11.2405045

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

Gas fueling by supersonic molecular beam injection (SMBI) has been performed at the central-cell in GAMMA 10. The results of SMBI experiment with plenum pressure from 0.3 MPa to 2.0 MPa were obtained using a laval nozzle. The distribution of the emission intensity during SMBI was investigated by the 2-dimensional image captured by the fast camera as an index of the neutral transport. The experimental results indicates that the effect of the laval nozzle reduces the dispersion of injected hydrogen molecules in the peripheral region. In this paper, we also studied the line density at the central-cell (NLcc) and Ha emission intensity during SMBI. Comparison between SMBI and conventional gas puffing is also discussed from the view point of the fueling efficiency.

DOI： 10.1585/pfr.11.2402053

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

In the hot ion mode of the tandem mirror GAMMA 10/PDX experiments, increases in the flux and temperature of end-loss electrons were observed after the excitation of Alfvén ion cyclotron (AIC) modes. The increase of the electron temperature in the central cell is directly observed using a Thomson scattering system, confirming electron heating due to the electron Landau damping of AIC modes.

DOI： 10.1585/pfr.11.2402051

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

I-Q (In-phase Quadrature) demodulator is one of key components in microwave interferometer system application. Normally, I-Q demodulator consists of amplifiers, mixers, 90 degree phase shifter, power divider and band-pass filters, and it is widely used in various microwave communication systems and measurement systems. In this paper, power divider and band-pass filters are newly designed as one single passive component, therefore, I-Q demodulator topology becomes simplified. The novel narrow band-pass filter type Wilkinson power divider not only provides extremely miniaturized circuit size, but also maintains the band-pass filter performance and power division function as well. One experimental circuit shows good agreement with the theoretical simulation.

DOI： 10.1088/1748-0221/10/11/C11005

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

A shear Alfvén wave at slightly below the ion-cyclotron frequency overcomes the ion-cyclotron damping and grows because of the strong anisotropy of the ion temperature in the magnetic mirror configuration, and is called the Alfvén ion-cyclotron (AIC) wave. Density fluctuations caused by the AIC waves and the ion-cyclotron range of frequencies (ICRF) waves used for ion heating have been detected using a reflectometer in a wide radial region of the GAMMA 10 tandem mirror plasma. Various wave-wave couplings are clearly observed in the density fluctuations in the interior of the plasma, but these couplings are not so clear in the magnetic fluctuations at the plasma edge when measured using a pick-up coil. A radial dependence of the nonlinearity is found, particularly in waves with the difference frequencies of the AIC waves; bispectral analysis shows that such wave-wave coupling is significant near the core, but is not so evident at the periphery. In contrast, nonlinear coupling with the low-frequency background turbulence is quite distinct at the periphery. Nonlinear coupling associated with the AIC waves may play a significant role in the beta- and anisotropy-limits of a mirror-confined plasma through decay of the ICRF heating power and degradation of the plasma confinement by nonlinearly generated waves.

DOI： 10.1063/1.4930216

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

This paper describes the recent results of divertor simulation research toward the realization of the detached plasma using the end-mirror of a large tandem mirror device. The additional ion cyclotron range of frequency heating in the anchor-cells for higher particle flux generation significantly increases the density, which attained the highest particle flux up to 1.7 × 10²³ particles/szm2 at the end-mirror exit. Massive gas injection (H2 and noble gases) into the divertor simulation experimental module (D-module) was performed, and a remarkable reduction of the electron temperature on the target plate was successfully achieved associated with the strong reduction of particle and heat fluxes in D-module. Two-dimensional images of Ha emission in D-module observed with a high-speed camera showed strong emission in the upstream region and significant reduction near the target plate. These results clarified the effect of radiation cooling and formation of detached plasma due to gas injection. It is also found that Xe gas is much more effective in achieving detached plasma than Ar gas. Numerical simulation studies also have been performed toward the understanding of the cooling mechanism of divertor plasma. The above results will contribute to establishment of detached plasma control and clarification of the radiation cooling mechanism toward the development of future divertor systems.

DOI： 10.13182/FST14-882

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

Abstract This paper describes the results of the experiments performed on Tandem Mirror device GAMMA 10/PDX mainly using a new "divertor simulation experimental module (D-module)" installed on one of the end mirror exits which is specially designed to investigate the physics of plasma detachment. The additional ICRF heating in the anchor-cells, connected to both ends of the central-cell, significantly increases the density in the both cells, which attained the generation of the highest particle flux up to 10²³ particles/s m² at the end-mirror exit. H₂ and noble gas injection to enhance the radiation cooling in D-module was performed and a remarkable reduction of the electron temperature (from few tens eV to <3 eV) on the target plate were successfully achieved associated with the strong reduction of particle and heat flux. A significant effect of simultaneous injection with hydrogen and noble gases for detached plasma formation was recognized for the first time.

DOI： 10.1016/j.jnucmat.2014.12.063

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

In GAMMA 10/PDX, the divertor simulation experiment has been performed recently. Ion cyclotron range of frequency (ICRF) waves are used for plasma production and ion heating. It is necessary for obtaining better controllability and extending the operational regime to understand the excitation, propagation, and absorption of the waves. The density fluctuations accompanied by the ICRF waves propagating in the inner region of plasma has been measured by using a microwave reflectometer on the antenna-phasing experiments, where the propagation of the ICRF waves is actively controlled. The phase difference between two axially separated ICRF antennas remarkably affects the global plasma parameters. The density fluctuation caused by the interfered ICRF waves is shown to depend clearly on the phase difference between the waves excited from two antennas. The availability of a reflectometer for the evaluation of the internal wave propagation is shown.

DOI： 10.13182/FST14-898

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

In the GAMMA 10 tandem mirror, divertor simulation experiments that utilize particle flux toward the west end region (called end-loss flux) have been implemented. Since a positive correlation has been reported between the end-loss flux and the central-cell density, an increase of the central-cell density is important for obtaining a higher end-loss flux on the divertor simulation experiments. By arranging the ion cyclotron range of frequency (ICRF) systems so as to excite strong ICRF waves in both anchor cells simultaneously, we have succeeded in producing high-density plasmas (line density of 1.2 × 10¹⁴ cm^-2) in both anchor cells. As a result, a higher central-cell density of 4.4 × 10¹² cm^-3and a higher end-loss flux of more than 10²³ m^-2s^-1have been obtained. One of the possible mechanisms of the high density production is a formation of positive potentials on both anchor cells. Plasmas in the central cell are confined due to those potentials.

DOI： 10.13182/FST14-890

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

Recent ICRF heating experiments performed in GAMMA 10/PDX are reported. Owing to antennaphasing technique and four ICRF antennas installed in the mirror cells other than the central cell, the operational regime of GAMMA 10/PDX is significantly extended. Several ICRF heating schemes to increase the parameters (plasma density in the central cell, particle flux flowing to the machine end and its ion temperature parallel to the field lines) are demonstrated. These results present positive progress in the ongoing divertor simulation experiments on GAMMA 10/PDX.

DOI： 10.13182/FST14-853

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

On the GAMMA 10 tandem mirror, divertor simulation experiments progress with high-temperature plasmas produced by waves in ion-cyclotron range of frequency (ICRF) and open magnetic fields. In these experiments, high-temperature and high-density plasmas are required to be produced and controlled. In order to enhance the ion heating in the anchor cell, phase-control experiments, which use two ICRF antennas installed in the central cell and the anchor cell, are introduced. In these experiments, ICRF waves in the same frequency (10 MHz) are excited. Ion heating in the anchor cell is performed more effectively with phase control. In order to analyze wave propagation in the phase-control experiments, a three-dimensional full wave code (TASK/WF), in which parallel processing has been implemented recently, is introduced. In this technical note, we discuss ICRF wave excitation and propagation in the phase-control experiments. It is clearly observed by the experiments and wave analysis that the enhancement of ion heating in the anchor cell is performed by phasecontrol experiments.

DOI： 10.13182/FST14-899

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

Development of high power gyrotrons and electron cyclotron heating (ECH) systems for the power modulation experiments in GAMMA 10 have been started in order to generate and control the high heat flux and to make the ELM (edge localized mode) like intermittent heat load pattern for divertor simulation studies. ECH for potential formation at plug region (P-ECH) produces electron flow with high energy along the magnetic filed line. By modulating the ECH power, we can obtain arbitrary pulse heat load patterns. By changing the on/off timing, we can simulate the ELM intermittent heat pulses. The heat flux factor increases almost linearly with ECH power. An intense axial electron flow with energy from hundreds of eV to a few keV generated by fundamental P-ECH is observed. When ECH is turned off, a short burst appears in the end loss ion current due to the axial drain of the confined plasma.

DOI： 10.1585/pfr.9.3402116

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

Results of the first experiment of short pulse plasma injection by MPD (magneto plasma dynamic) Jet into GAMMA 10/PDX's longer pulse plasma are reported. In the experiment, a new method for plasma start-up without using plasma guns was applied. In this method, the main plasma of GAMMA 10/PDX was produced by ECRH (electron cyclotron resonance heating) and ICRF (ion cyclotron range of frequency). Then, MPD Jet plasma was injected into the main plasma along magnetic field line. As a result, density of the main plasma was increased and the end-loss flux was doubled. Flow velocity of the plasmoid injected by the MPD Jet was evaluated from the change of plasma density in each cell of the tandem mirror. The result indicated that the flow speed is several km/s. It is found that the plasmoid worked as strong fueling device which dramatically raises the density of plasma. Therefore injection of MPD Jet plasma into tandem mirror can be a useful tool to study physical phenomena of divertor and PWI.

DOI： 10.1585/pfr.9.3406098

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

Plasmas with high ion temperature of several kiloelectronvolts and a strong temperature anisotropy of greater than 10 were produced by ion cyclotron range of frequency (ICRF) heating in the GAMMA 10 tandem mirror. In such high-performance plasmas with strong anisotropy, high-frequency fluctuations, so-called Alfvén-ion-cyclotron (AIC) waves, are excited spontaneously. These AIC waves have several discrete peaks in the frequency spectrum. Coupling of the ICRF heating waves and the excited AIC waves was clearly observed in the density fluctuations measured with a newly developed reflectometer. Parametric decay from the heating ICRF waves to the AIC waves and low-frequency waves was also indicated. Alfvén waves with difference frequencies between the discrete peaks of the AIC waves were detected in a signal that measured the number of axially transported high-energy ions (over 6 keV) at the machine end, indicating pitch-angle scattering caused by the low-frequency waves. Energy transport along the magnetic field line is an important consideration when ICRF power is injected in the perpendicular direction to a magnetic field line. The importance of the spontaneously excited AIC waves for axial confinement of a tandem mirror through wave-wave couplings was demonstrated.

DOI： 10.1088/0029-5515/53/7/073040

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

A correlation between drift-type fluctuations and anomalous radial transport was observed in GAMMA 10, and these fluctuations were suppressed by the electron-cyclotron-heating-driven radial electric field. We developed new diagnostics to conduct these studies: a simultaneous two-point-measurement gold neutral beam probe (GNBP) for the radial electric field and potential fluctuations, and a high-speed end-plate potential fluctuation measurement system. The electric field and its fluctuations were successfully obtained in a single plasma shot for the first time. Coherence between the drift-type potential fluctuations measured in the core plasma by the GNBP and those obtained by end-plate measurements was clearly observed. These potential and electric field fluctuations were clearly suppressed by the positive electric fields measured by two-point potential measurements using the GNBP and the end-plate system. We can obtain a powerful tool for probing the radial electric field and potential fluctuations in the core plasma because the end-plate potential fluctuation is the same as that in the core plasma measured using the new GNBP.

DOI： 10.1088/0029-5515/53/7/073031

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

Self-generation and sustainment of toroidal flux via a dynamo is one of the unique characteristics of the reversed-field pinch (RFP) configuration. In a small aspect ratio RFP machine RELAX, it has been observed that a sudden dynamo usually occurs at a localized toroidal location. This localized dynamo evolves in time, causing a toroidally asymmetric flux distribution. The degree of asymmetry depends on the location and propagation of the localized dynamo. It has been observed that the position where the localized dynamo occurs coincides with the position where the phases of the internally resonant tearing modes align. The phase alignment plays an important role in triggering a localized dynamo activity and in the formation of asymmetric toroidal flux distribution especially in deep-reversal plasmas in RELAX.

DOI： 10.1088/0741-3335/55/1/015005

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

This paper describes the results of characterization of high heat and particle fluxes produced at the end-cell of the large tandem mirror GAMMA 10 and of the initial plasma-irradiation experiments. In the case of ICRF plasmas, the heat flux of 0.8 MW/m² and the particle flux of 4 × 10 ²²/m² s were achieved at the end-mirror exit. The heat flux increases with the ICRF power and has a linear relationship with the stored energy. Direct ion energy analysis clarified that the parallel ion temperature can be controlled from 100 eV to 400 eV by changing the ICRF power. Additional plasma heating using another ICRF system in the anchor-cell significantly increases the particle flux, which gives a clear prospect of generating the higher particle flux by applying additional ICRF heating in the neighboring cells. The initial results of the plasma-gas-material interactions on a new V-shaped tungsten target were also reported.

DOI： 10.1016/j.jnucmat.2013.01.157

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

The end-loss ion flux in GAMMA 10 is measured with a view to use it for a divertor simulation experiment or other studies that require high-performance plasma flux. First, the basic parameters of the end-loss ion flux, such as its energy and current density, were measured in typical plasma shots in GAMMA 10. A diagnostic device, the end loss ion energy analyzer (ELIEA), was used to the measure these parameters. An investigation of the relationship between the parameters of the end-loss ion flux and the plasma parameters in the central- cell revealed linear-like relationships between these parameters. We also analyzed the effects of plasma heating and fueling by using devices installed in GAMMA 10 (ion cyclotron resonance frequency (ICRF), electron cyclotron resonance heating (ECRH) and supersonic molecular beam injection (SMBI)) in order to generate more intense ion flux. The results showed that the energy distribution of the ion flux is more closely resembles a double component Maxwellian than a simple Maxwellian. Plasma heating schemes such as ECRH and ICRF are found to be effective for the generation of a more intense ion flux.

DOI： 10.1585/pfr.7.2405147

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

On GAMMA10, waves in Ion-Cyclotron Range of Frequency (ICRF) are used to produce initial plasmas, heat plasmas and keep magneto-hydrodynamic (MHD) stability. High performance plasmas in the minimum- B configuration supply MHD stability. In order to enhance plasma heating, we introduce an ICRF system for heating plasmas in the anchor cell and evaluate its antenna loading. Changing the antenna shape is expected to improve antenna loading. In the experiment, we confirm to increase the antenna loading by changing the antenna shape from simple bar-type to the double elliptic arc type.

DOI： 10.1585/pfr.7.2402136

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

DOI： 10.1143/JPSJ.81.115001

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

A new interferometer is installed on the west anchor cell of the GAMMA 10 tandem mirror. In GAMMA 10, we have used a heterodyne-type interferometer with a 70-GHz IMPATT oscillator and a 150-MHz oscillator for frequency modulation. The new interferometer consists of a 17.5-GHz phase locked dielectric resonator oscillator and a 37.5-MHz temperature-compensated crystal oscillator, as well as frequency multipliers. The main motivation for the new interferometer using frequency multipliers is to achieve a stable and cost effective interferometer. Direct anchor heating experiments with new anchor ion cyclotron range of frequency antennas in both the west and the east anchor cells are carried out. Density increases in both anchor cells are clearly observed using the new interferometer.

DOI： 10.1063/1.4731006

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

A fast successive soft-X ray (SXR) imaging system where SXR camera and high-speed camera for the study of time evolution of magnetic islands has been constructed. A preliminary experimental result in which we observed tangential SXR images from quasi-periodic quasi-single helicity (QSH) state in low-aspect-ratio (low-A) reversed field pinch (RFP) is presented. We successfully obtained time evolution of SXR images from tangential port. By comparison obtained images with simulated images, we may conclude that the evolution of experimental SXR image suggests the rotating QSH RFP configuration. The filamentous configuration tends to be observed in QSH state rather than in multi-helicity (MH) state.

DOI： 10.1585/pfr.6.2406096

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

Suppression of the radial transport of the particles caused by low-frequency density fluctuations is one of the important subjects in the GAMMA10 tandem mirror. In GAMMA10, plasmas are mainly produced and heated with Ion Cyclotron Range of Frequency (ICRF) waves. The plasmas heated with ICRF waves have strong temperature anisotropy, because the ions are accelerated perpendicularly to the magnetic field line. In the GAMMA10 experiments, two types of low-frequency density fluctuations are observed; one is a drift-type fluctuation and the other is a flute-type fluctuation. In this paper, we study the radial transport of ICRF-produced high-energy ions which is caused by the low-frequency density fluctuations.

DOI： 10.1585/pfr.6.2402152

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

Spatiotemporal behavior of Alfvén-ion-cyclotron (AIC) waves excited in GAMMA10 is investigated using a microwave reflectometer and magnetic probes located at the edge. The frequency spectrum of the AIC waves has several discrete peaks. Simultaneous measurement of the internal density fluctuation and edge magnetic fluctuation of AIC waves shows that AIC waves have different radial structures in the initial excitation phase, but in the later steady state, each of them has the same structure in the radial direction. The results indicate that several AIC waves are excited as the same eigenmode in the radial direction.

DOI： 10.1585/pfr.6.2402047

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

Study of helical structure has been in progress in shallow reversal reversed field pinch (RFP) plasmas in a lowaspect- ratio machine RELAX (R=a = 0:5 m/0.25 m, A = 2) by using visible light and soft-X-ray (SXR) imaging diagnostics. Simple helix and its toroidal rotation have been observed in tangential visible light images taken by a highspeed camera. Similar simple filament structures have also been observed in tangential images obtained by a pin-hole SXR camera assembled with Image-intensified charged coupled device (ICCD). The SXR experimental images have been compared with calculated tangential images using model profiles for emissivity to identify the plausible SXR emissivity profile. It has been found that a model profile of helical core having SXR emissivity 2-4 times higher than the background provides 2D SXR images in reasonable agreement with the experimental results. Time evolution of the SXR emissivity profile measured with a photodiode array has shown that the emissivity is the highest in the core region with a quasi-periodic oscillation of the peak position.

DOI： 10.1143/JPSJ.80.114501

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

A hot helical structure in low-aspect-ratio (A) reversed field pinch (RFP) is obtained with the soft X-ray (SXR) imaging technique. Tangential SXR imaging camera and high-speed camera system is applied to low-A RFP for studying quasi-single-helicity RFP state. The helical structure correlated with m = 1/n = 4 tearing mode is identified by means of a subtraction technique.

DOI： 10.1109/TPS.2011.2160369

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

Operational regimes have been investigated over a wide range of discharge parameters in a low-aspect-ratio (low-A) reversed field pinch (RFP) RELAX. Two distinctive regimes have been identified, possibly characteristic to low-A RFP. One is a very shallow-reversal regime, and the other is an extremely deep-reversal regime where a field-reversal parameter lower than-1 could be sustained. Innewly attained extremely deep-reversal plasmas, the amplitudes of the resonant modes were suppressed to a lower level with enhanced soft-x-ray emission intensity. The extremely deep-reversal regime in low-A RFP may have a potential to become a new operational regime with improved plasma performance.

DOI： 10.1088/0741-3335/53/2/025003

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

In the GAMMA 10 tandem mirror, Magneto Hydro Dynamic (MHD) stabilization is kept with quadruple minimum-B anchor configuration. In the previous heating experiments, Ion-Cyclotron Range of Frequency (ICRF) antenna installed in the central cell was used for the anchor heating. Fast Alfvén wave excited in the central cell is partly converted to the slow wave in the nonaxisymmetric transition region between the central and the anchor cells, and heats ions in the minimum-B well. In order to produce higher performance plasmas in the central cell, the ion heating should be enhanced in the anchor cell. In this study, an experiment is carried out in the anchor cell to heat ions by ICRF waves without mode conversion. A bar-type antenna is installed in the anchor cell. Applied frequency is adjusted to ion-cyclotron resonance frequency in the minimum-B well. By the additional ion heating with the bar-type antenna, remarkable increase in the diamagnetic signal has been observed in the anchor cell. It is confirmed that the additional heating by the bar-type antenna can also keep MHD stabilization.

DOI： 10.13182/FST11-A11625

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

Recent progress and near future plan of GAMMA 10 efforts are presented. With high power plug electron cyclotron heating (ECH) up to ~ 400 kW, the ion confining potential of more than 2 kV was confirmed. The drift type low frequency fluctuations were suppressed by the positive radial electric field produced by plug ECH. It is found that the efficient EC heating on mirror devices from a strong B field side requires the minimization of the stray microwave in addition to the 100% X-mode excitation to avoid the enhancement of the ion loss. The development of a gyrotron, the key tool of these ECH experiments, has been made in collaboration with NIFS (National Institute for Fusion Science), More than 1.5 MWfor more than Is has been demonstrated at 77GHz. The plan of the boundary plasma research program with modification of GAMMA 10 is in progress. The new program includes the physics and technology studies of the divertor and SOL plasmas and PWI relevant to torus plasmas like ITER. The high heat flux experiments using the open end mirror throat has been started and we have obtained successful preliminary data, which include the heat flux of 8 MW/m².

DOI： 10.13182/FST11-A11563

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

Plasmas with high ion-temperature of several keV have been produced by using ion-cyclotron range of frequency (ICRF) heating in the GAMMA 10 tandem mirror. In such high performance plasmas, high and lowfrequency fluctuations are excited and ions trapped in the magnetic field interact with such fluctuations. Three types of wave-particle interactions have been observed in the GAMMA 10 tandem mirror. The turning point diffusion near the ion cyclotron resonance layer has been observed in minimum-B configuration on the anchor cell. Pitch angle scattering of high-energy ions due to the AIC modes and low-frequency waves which have differential frequencies between discrete peaks of the AIC modes are clearly detected. The drift-type fluctuations are clearly observed in the central cell. By using a semiconductor detector, high-energy ions are detected at the radial location far from the plasma edge. The fluctuation, of which frequency is the same as that of drift-type fluctuation, is observed in the signal of high-energy ions. From the pitch angle distribution of the phase differences between both fluctuations, radial transport of high-energy ions caused by drift-type fluctuations near their turning points in the confining mirror field is suggested in the experiments.

DOI： 10.13182/FST11-A11583

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

Tangential soft-x ray (SXR) imaging diagnostic has been developed and three-dimensional (3D) structure of the internal magnetic surface has been deduced by comparing the experimental and calculated two-dimensional SXR images in a reversed field pinch. The SXR imaging system, consisting of a MCP, a fluorescent plate, and an intensified charge coupled device camera, has been installed in REversed field pinch of Low-Aspect-ratio eXperiment (RELAX) machine. Major characteristics of an experimental SXR image could be reproduced by numerical calculations of the image using a single island model, suggesting a helical hot core in RELAX. The SXR imaging system could be useful for 3D structural studies when tangential and vertical simultaneous imaging systems would be installed, with appropriate numerical modeling of 3D structure of the magnetic surfaces.

DOI： 10.1063/1.3455216

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

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

The low-aspect-ratio (A) reversed field pinch (RFP) offers attractive properties such as enhanced bootstrap current and simpler MHD mode dynamics. The RELAX (REversed field pinch of Low-Aspect ratio eXperiment) machine with the world's lowest A of 2 (R/a = 0.5 m/0.25 m) has been constructed to explore the RFP properties in low-A regime. In flat-topped low-A RFP discharges in RELAX, plasma current of ~50 kA has been attained with discharge duration of ~2 ms. In round-topped discharges with plasma current of ~70 kA, quasi-periodic growth of a single helical mode has been observed. When the dominant m = 1/n = 4 mode grows, the toroidal mode spectrum looks like that of the quasi-single helicity (QSH) RFP state with higher amplitude. MHD equilibrium analyses using a reconstruction code have shown that the bootstrap current fraction is lower than ~5% in the present RELAX plasmas, and it will be ~25% if we could achieve the plasma density of 4 × 10 ¹⁹ m ^-3 and electron temperature of 300 eV at plasma current of ~100 kA.

DOI： 10.1007/s10894-008-9172-z

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

A neoclassical equilibrium for low-aspect-ratio reversed field pinch (RFP) plasma is reconstructed from initial experimental results of the standard discharge in a low-aspect-ratio RFP device (RELAX). We estimate the magnitude of the bootstrap current, which is a self-induced plasma parallel current, from the reconstructed equilibrium, and illustrate how the bootstrap current depends on plasma parameters.

DOI： 10.1143/JPSJ.78.013501

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

DOI： 10.1143/JPSJ.77.075005

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

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

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

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

A reversed field pinch (RFP) machine with aspect ratio of as low as 2 (R/a = 0.51 m/0.25 m) has been constructed for the experimental study of new RFP regime. Low-aspect ratio RFP plasmas have been produced in a resistive wall vacuum vessel for the first time. Initial results on discharge characteristics of the low-A RFP plasmas are presented. This experiment serves our study on new RFP regime with expected characteristics of simpler MHD dynamic arising from equilibrium profiles with less densely spaced rational surfaces of the dominant modes, which have been revealed by the recent progress in RFP research.

DOI： 10.1143/JPSJ.76.123501

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

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

In recent years, reversed field pinch (RFP) research has demonstrated great progress which alters conventional RFP concepts and introduced new RFP regime such as current profile control and new MHD mode dynamics. The low-aspect ratio (low-A) RFP configuration may have some advantages to explore these new regimes. After a brief description on the new RFP regimes, we will discuss our research plans in a low-A RFP which is under construction.

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

Event date： 2022.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：富山国際会議場   Country：Japan  

Event date： 2022.11

Language：English   Presentation type：Oral presentation (general)  

Venue：Online   Country：Japan  

Event date： 2022.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Other  

Event date： 2022.3

Language：Japanese   Presentation type：Symposium, workshop panel (public)  

Venue：オンライン   Country：Other  

Event date： 2021.11 - 2021.12

Language：Others   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Other  

Event date： 2021.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Other  

Behavior of high-frequency modes excited in a non-inductively driven QUEST plasma

Event date： 2021.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Other  

Event date： 2021.3

Language：Others   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Other  

Event date： 2021.1

Language：English   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Other  

Event date： 2020.12

Language：Others   Presentation type：Oral presentation (general)  

Venue：オンライン   Country：Other  

Effects of X-rays on a high-energy particle measurement on QUEST

Event date： 2019.11 - 2019.12

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：中部大学   Country：Japan  

Event date： 2019.10

Language：English  

Venue：Fort Lauderdale, Florida   Country：United States  

Event date： 2019.9

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京大学理学部   Country：Japan  

Event date： 2018.12

Language：Japanese  

Venue：大阪大学   Country：Japan  

Event date： 2018.11

Language：English  

Venue：Portland, Oregon   Country：United States  

Event date： 2018.8

Language：English   Presentation type：Oral presentation (general)  

Venue：Univ. of Tsukuba   Country：Japan  

Event date： 2018.6

Language：Japanese  

Venue：九州大学筑紫キャンパス   Country：Japan  

Event date： 2018.2

Language：English   Presentation type：Oral presentation (general)  

Venue：Institute of Advanced Energy, Kyoto Univ.   Country：Japan  

Language：Japanese  

Venue：日本 東北大学工学研究科   Country：Other  

GAMMA 10/PDXにおける高速イオンの軸方向輸送解明に向けた波動計測の高度化

Language：English  

Venue：Novosibirsk, RUSSIA   Country：Other  

RADIAL TRANSPORT OF HIGH-ENERGY IONS CAUSED BY LOW-FREQUENCY FLUCTUATIONS IN THE GAMMA10 TANDEM MIRROR

Language：English  

Venue：Novosibirsk, RUSSIA   Country：Other  

ION-CYCLOTRON RESONANCE HEATING EXPERIMENT IN THE QUADRUPLE MINIMUM-B FIELD ON GAMMA 10

Language：English  

Venue：Japan Toki   Country：Other  

Analysis of End-Loss Ion Flux for Application Studies of the Plasma Flow from the End Mirror Exit of GAMA 10

Language：English  

Venue：Germany   Country：Other  

Recent Results of Divertor Simulation Research Using an End-cell of a Large Tandem Mirror Device

Language：English  

Venue：Tsukuba, JAPAN   Country：Other  

TWO-POINT MEASUREMENT OF HIGH-FREQUENCY DENSITY FLUCTUATIONS BY REFLECTOMETRY IN GAMMA 10

Language：English  

Venue：Tsukuba, JAPAN   Country：Other  

TIME EVOLVING STRUCTURE OF ALFVEN ION-CYCLOTRON WAVES IN GAMMA10

Language：English  

Venue：日本 Tsukuba   Country：Other  

TIME EVOLVING STRUCTURE OF ALFVÉN ION-CYCLOTRON WAVES IN GAMMA10

Language：English  

Venue：JAPAN Tsukuba   Country：Other  

Recent ICRF heating experiments for a divertor simulation study on GAMMA 10

Language：English  

Venue：JAPAN Tsukuba   Country：Other  

ICRF experiment with phase-controlled antennas on GAMMA10

Language：English  

Venue：Tsukuba, JAPAN   Country：Other  

ICRF HEATING EXPERIMENTS IN BOTH EAST AND WEST ANCHOR CELLS ON GAMMA10

Language：English  

Venue：Tsukuba, JAPAN   Country：Other  

ICRF ANTENNA LOADING IN THE MINIMUM-B ANCHOR CONFIGURATION ON GAMMA 10

Language：English  

Venue：JAPAN Tsukuba   Country：Other  

Evaluation of the Axisymmetricity of the Central-cell Plasma Using a Segmented Limiter on GAMMA 10

Language：English  

Venue：Tsukuba, JAPAN   Country：Other  

EDGE TURBULENCE/FLUCTUATION OBSERVATION AT "HIGH DENSITY MODE" IN GAMMA 10 BY FAST CAMERA

Language：English  

Venue：Tsukuba, JAPAN   Country：Other  

AXIAL TRANSPORT OF HIGH-ENERGY IONS DUE TO ICRF HEATING ON GAMMA 10

Language：English  

Venue：USA San Diego   Country：Other  

Coupling of ICRF Waves and Axial Transport of High-Energy Ions Owing to Spontaneously Excited Waves in the GAMMA 10 Tandem Mirror

Language：Japanese  

Country：Other  

ガンマ10アンカー部に於ける半導体検出器を用いたICRF加熱プラズマ計測

Language：Japanese  

Country：Other  

GAMMA10セントラル部におけるイオンエネルギーバランスの解析

Language：Japanese  

Country：Other  

GAMMA10エンド部における高密度イオン流の生成

Language：Japanese  

Venue：日本 福岡   Country：Other  

GAMMA10におけるAlfvén ion-cyclotron波動の励起特性

Language：English  

Venue：Japan JAEA Naka Fusion Institute   Country：Other  

Measurement of spontaneously excited ICRF waves by reflectometry in GAMMA10

Language：English  

Venue：Japan Nara   Country：Other  

ICRF waves excited by strong ion-temperature anisotropy and those interactions with high-energy ions in the GAMMA10 tandem mirror

Language：English  

Venue：Korea Busan   Country：Other  

Coupling of ICRF waves and related axial transport of high-energy ions in GAMMA 10

Language：Japanese  

Venue：日本 核融合科学研究所   Country：Other  

GAMMA10における自発励起波動と高エネルギーイオンの軸方向輸送

Language：English  

Venue：Japan Toki   Country：Other  

The first experiment of MPD Jet injection into GAMMA 10 plasma

Language：English  

Venue：USA MIT, Boston   Country：Other  

Recent ICRF-related experiments on the GAMMA10 tandem mirror

Language：English  

Venue：Japan Toki   Country：Other  

Generation and Control of High Intermittent Heat Load Pattern for Divertor Simulation Studies in GAMMA 10 Tandem Mirror

Language：English  

Venue：USA Denver   Country：Other  

Coupling and spatial structure of Alfven-ion-cyclotron waves in GAMMA 10

Language：English  

Venue：Japan Toki   Country：Other  

Analysis of ICRF wave excitation in phase-control experiment on GAMMA10

Language：Japanese  

Venue：東京工業大学 大岡山キャンパス   Country：Other  

高速カメラとプローブを用いたGAMMA10プラズマ計測

Language：Japanese  

Venue：日本 大岡山   Country：Other  

大型タンデムミラー装置を用いたダイバータ模擬の為の大熱流束プラズマの発生と非接触プラズマ実現に向けた研究の進展

Language：Japanese  

Venue：東京工業大学 大岡山キャンパス   Country：Other  

半導体検出器を用いた吸収法によるガンマ10 アンカー部プラズマ計測

Language：Japanese  

Venue：東京工業大学 大岡山キャンパス   Country：Other  

GAMMA10ダイバータ模擬実験に向けたMPDJetの適用

Language：Japanese  

Venue：日本 東京工業大学   Country：Other  

GAMMA10セントラル部プラズマの高温高密度化に向けたICRF加熱方法の検討

Language：Japanese  

Venue：日本 東京工業大学   Country：Other  

GAMMA10セントラル部における高周波波動の空間構造および非線形結合現象

Language：Japanese  

Venue：東京工業大学 大岡山キャンパス   Country：Other  

GAMMA10セントラル部における高周波波動の空間構造および非線形結合現象

Language：Japanese  

Venue：日本 東京工業大学   Country：Other  

GAMMA10アンカー部における高周波密度揺動の振る舞いと定量評価に向けた取り組み

Language：Japanese  

Venue：日本 東京工業大学   Country：Other  

GAMMA10における高周波加熱時の高エネルギーイオン輸送

Language：Japanese  

Venue：日本 東京工業大学   Country：Other  

GAMMA10における高周波加熱時の高エネルギーイオン輸送

Language：Japanese  

Venue：日本 東京工業大学   Country：Other  

GAMMA10における高周波加熱印加時の分割リミターを用いた浮遊電位計測

Language：Japanese  

Venue：日本 東京工業大学   Country：Other  

GAMMA10におけるプラズマパラメータ制御に向けたICRF加熱実験および3次元波動解析

Language：Japanese  

Venue：東京工業大学 大岡山キャンパス   Country：Other  

GAMMA10/PDX実験におけるカロリーメーターを用いた熱流計測

Language：Japanese  

Venue：東京工業大学 大岡山キャンパス   Country：Other  

GAMMA10 SMBI 実験における侵入長の評価

Language：Japanese  

Venue：日本 東京工業大学   Country：Other  

GAMMA 10プラグ/バリア部におけるICRF加熱実験

Language：Japanese  

Venue：東京工業大学 大岡山キャンパス   Country：Other  

GAMMA 10 セントラル部におけるイオンエネルギーバランスの時間発展解析

Language：Japanese  

Venue：東京工業大学 大岡山キャンパス   Country：Other  

GAMMA 10 E-Div.プラズマにおける中性粒子効果のシミュレーション解析

Language：English  

Venue：Japan Fukui   Country：Other  

ICRF Experiments Toward the Enhancement of End-Loss Flux on GAMMA 10/PDX

Language：Japanese  

Venue：日本 東北大学   Country：Other  

大型タンデムミラー装置GAMMA10における磁力線方向への粒子輸送

Language：Japanese  

Venue：日本 核融合科学研究所   Country：Other  

GAMMA10における高周波位相制御実験および波動解析

Language：Japanese  

Venue：日本 核融合科学研究所   Country：Other  

GAMMA 10におけるマイクロ波反射計を用いたICRF波動計測

Language：Japanese  

Venue：横浜パシフィコ   Country：Other  

ミラー磁場中のアルベン波動の自発励起とイオンとの相互作用

Language：English  

Venue：Japan Ishikawa   Country：Other  

Progress of divertor simulation research toward the realization of detached plasma using a large tandem mirror device

Language：Japanese  

Venue：つくば国際会議場   Country：Other  

マイクロ波反射計で計測したGAMMA 10プラズマ内部領域におけるICRF波動の振る舞い

Language：Japanese  

Venue：つくば国際会議場   Country：Other  

GAMMA10アンカー部及びバリア部ICRF加熱によるセントラル部プラズマの高密度化

Language：Japanese  

Venue：つくば国際会議場   Country：Other  

GAMMA10における高周波アンテナ間位相制御時の波動解析

Language：Japanese  

Venue：つくば国際会議場   Country：Other  

GAMMA 10における自発励起ICRF波動の構造計測と高速イオン損失への影響

Language：Japanese  

Venue：つくば国際会議場   Country：Other  

GAMMA 10/PDXダイバータ模擬実験に向けた端損失粒子フラックスの制御

Language：Japanese  

Venue：つくば国際会議場   Country：Other  

ELM模擬に向けたECH入射電力変調/位置制御による高熱流束生成の基礎実験

Language：Japanese  

Venue：つくば国際会議場   Country：Other  

ELM模擬に向けたECH入射電力変調/位置制御による高熱流束生成の基礎実験

Language：English  

Venue：Korea Daejeon   Country：Other  

Study of the end-loss ion flux of GAMMA 10/PDX experiments with an additional ICRF wave

Language：English  

Venue：Korea Daejeon   Country：Other  

Recent results of divertor simulation experiments using D-module in the GAMMA 10/PDX tandem mirror

Language：English  

Venue：Korea Daejeon   Country：Other  

RECENT RESULTS OF DIVERTOR SIMULATION EXPERIMENTS USING D-MODULE IN THE GAMMA 10/PDX TANDEM MIRROR

Language：English  

Venue：Korea Daejeon   Country：Other  

Present Status of GAMMA 10/PDX Project

Language：English  

Venue：Korea Daejeon   Country：Other  

Internal measurement of propagation of ICRF waves by using reflectometers on GAMMA10

Language：English  

Venue：Korea Daejeon   Country：Other  

High-density plasma production in the GAMMA10 central cell with ICRF heating on both anchor cells

Language：English  

Venue：Korea Daejeon   Country：Other  

Extension of operational regimes with ICRF heating on GAMMA 10/PDX

Language：English  

Venue：Korea Daejeon   Country：Other  

Code Development for the Calculations of the Multi-frequency Oscillations and Startup in the Cavity of the Future High-Power Gyrotrons

Language：English  

Venue：Korea Daejeon   Country：Other  

Analysis of wave excitation of the phase-control ICRF antennas with theree dimensional full wave code on GAMMA 10

Language：English  

Venue：US New Orleans   Country：Other  

On the nonlinear couplings among ICRF waves observed in GAMMA 10

Language：English  

Venue：Russian Federation St. Petersburg   Country：Other  

Development of Divertor Simulation Research in the GAMMA 10/PDX Tandem Mirror

Language：Japanese  

Venue：朱鷺メッセ   Country：Other  

GAMMA10/PDXアンカー部加熱実験におけるエンド部フラックス挙動の計測と数値計算による解析

Language：Japanese  

Venue：朱鷺メッセ   Country：Other  

GAMMA10/PDXにおけるアンカー部高周波加熱とセントラル部密度揺動との相関

Language：Japanese  

Venue：朱鷺メッセ   Country：Other  

GAMMA 10セントラル部におけるICRF波動間の非線形結合

Language：Japanese  

Venue：朱鷺メッセ   Country：Other  

GAMMA 10における反射計を用いたICRF波動伝搬計測

Language：Japanese  

Venue：Japan Tokimesse, Niigata   Country：Other  

Generation and characterization of detached plasma in the GAMMA 10/PDX end-cell

Language：Japanese  

Venue：朱鷺メッセ、新潟   Country：Other  

Generation and characterization of detached plasma in the GAMMA 10/PDX end-cell

Language：Japanese  

Venue：朱鷺メッセ   Country：Other  

3次元波動コードを用いたGAMMA 10極小磁場配位におけるICRF波動解析

Language：English  

Venue：Korea Daejeon   Country：Other  

Measurement of density fluctuation of ICRF waves using a reflectometer in GAMMA 10

Language：Japanese  

Venue：核融合科学研究所   Country：Other  

GAMMA 10セントラル部におけるICRF波動間の結合に関する解析

Language：Japanese  

Venue：日本 つくばサイエンス・インフォメーションセンター   Country：Other  

GAMMA 10/PDXダイバータ模擬実験に向けたICRFによる熱及び粒子束制御の進展

Language：English  

Venue：Germany Juelich   Country：Other  

Analysis of neutral particle recycling and pumping in detached plasma experiments in the D-module of GAMMA 10/PDX

Language：English  

Venue：Sapporo, JAPAN   Country：Other  

A narrow band-pass filter type Wilkinson power divider for I-Q demodulator in microwave interferometer system

Language：Japanese  

Venue：日本 名古屋大学、名古屋   Country：Other  

大型タンデムミラーを用いた非接触プラズマ生成とその特性評価の進展

Language：Japanese  

Country：Other  

大型タンデムミラーを用いた非接触プラズマ生成とその特性評価の進展

Language：Japanese  

Venue：日本 名古屋大学東山キャンパス・豊田講堂   Country：Other  

吸収法による半導体検出器を用いたガンマ10アンカー部プラズマ計測

Language：English  

Venue：Japan Toki   Country：Other  

Study of the axial plasma confinement for high particle flux operations in GAMMA 10/PDX

Language：English  

Venue：US Savannah   Country：Other  

Measurement of the ICRF wave propagation in the internal region of plasmas by using reflectometers on GAMMA10

Language：Japanese  

Venue：日本 名古屋大学東山キャンパス・豊田講堂   Country：Other  

GAMMA10高温プラズマ中のアルベン波動の2点相関

Language：Japanese  

Venue：日本 名古屋大学東山キャンパス・豊田講堂   Country：Other  

GAMMA10内部領域における反射計を用いたICRF波動の吸収と伝搬計測

Language：Japanese  

Venue：日本 名古屋大学東山キャンパス・豊田講堂   Country：Other  

GAMMA10セントラル部におけるマイクロ波反射計を用いた低周波波動励起の観測

Language：Japanese  

Venue：日本 名古屋大学、名古屋   Country：Other  

GAMMA10におけるセントラル部プラズマとエンドプレートでの電位揺動解析

Language：Japanese  

Venue：日本 名古屋大学、名古屋   Country：Other  

GAMMA10/PDXダイバータ模擬実験における水素ガス追加供給により形成された非接触プラズマの電子温度・密度計測

Language：Japanese  

Venue：日本 名古屋大学東山キャンパス・豊田講堂   Country：Other  

GAMMA10/PDXにおけるプラグ／バリア部ICRF高周波を用いた端損失プラズマ制御実験

Language：Japanese  

Venue：日本 名古屋大学東山キャンパス・豊田講堂   Country：Other  

GAMMA 10/PDXにおけるアンカー部ICRF加熱によるプラズマの高密度化

Language：Japanese  

Venue：日本 名古屋大学、名古屋   Country：Other  

GAMMA 10/PDXにおける高粒子束生成に向けた軸方向プラズマ輸送の研究

Language：English  

Venue：US Savannah   Country：Other  

Excitation of low-frequency waves via coupling between slow Alfvén waves in the GAMMA 10 tandem mirror

Language：English  

Venue：Japan Toki   Country：Other  

Effect of Laval Nozzle in the GAMMA 10 SMBI Experiments

Language：English  

Venue：Japan Toki   Country：Other  

Direct observation of electron heating by electron Landau damping of Alfvén ion cyclotron waves with Thomson scattering system in the tandem mirror GAMMA 10/PDX

Language：Japanese  

Venue：日本 核融合科学研究所   Country：Other  

ICRF加熱を用いたGAMMA10/PDX高密度化実験

Language：Japanese  

Venue：日本 東北大学   Country：Other  

GAMMA10/PDXにおけるダイバータ模擬を目指したICRF加熱実験

Language：English  

Venue：Italy Rome   Country：Other  

Impact of gas injection on detached plasma formation in divertor simulation experiments using the GAMMA 10/PDX tandem mirror

Language：Japanese  

Venue：日本 九州大学伊都キャンパス椎木講堂   Country：Other  

反射計を用いたGAMMA 10アンカー部ICRF加熱時の密度分布の変動と揺動の同時計測

Language：Japanese  

Venue：日本 つくばイノベーションプラザ   Country：Other  

GAMMA 10における温度非等方性緩和機構の解明に向けたICRF波動計測の進展

Language：English  

Venue：Russia Federation Budker Inst Nucl Phys, Akademgorodok, RUSSIA   Country：Other  

Recent Results of Characterization of Detached Plasma in Divertor Simulation Experiments Using the GAMMA 10/PDX Tandem Mirror

Language：English  

Venue：Budker Inst Nucl Phys, Akademgorodok, RUSSIA   Country：Other  

Overview of Recent Progress and Future in GAMMA 10/PDX Project

Language：English  

Venue：Budker Inst Nucl Phys, Akademgorodok, RUSSIA   Country：Other  

ICRF Heating in the Plug/Barrier Region to Control End-Loss Ions on GAMMA 10/PDX

Language：English  

Venue：Budker Inst Nucl Phys, Akademgorodok, RUSSIA   Country：Other  

Development of Internal ICRF Wave Detection Using Microwave Reflectometry on GAMMA 10

Language：English  

Venue：Budker Inst Nucl Phys, Akademgorodok, RUSSIA   Country：Other  

Characteristics of SMBI Fueling with Laval Nozzle in GAMMA 10 Based on Experimental and Simulation Results

Language：Japanese  

Venue：日本 金沢大学角間キャンパス   Country：Other  

JT-60UにおけるDD核融合生成3Heに起因するイオンサイクロトロン放射の密度依存性

Language：English  

Venue：Kyoto International Conference Center   Country：Other  

Spatial Structure of Spontaneously Excited ICRF Waves and Relevant High-Energy Ion Loss in the GAMMA 10 Tandem Mirror

Language：English  

Venue：Japan Kyoto   Country：Other  

Recent Progress of Divertor Simulation Research Using the GAMMA 10/PDX Tandem Mirror

Language：English  

Venue：US San Jose   Country：Other  

Probing of high-frequency coherent fluctuations by using a two-channel microwave reflectometer with antenna switching

Language：English  

Venue：USA San Jose   Country：Other  

Probing of high-frequency coherent fluctuations by using a two-channel microwave reflectometer with antenna switching

Language：English  

Venue：Japan Kyoto   Country：Other  

Present Status and Future of Divertor Simulation Research Using the GAMMA 10 /PDX Tandem Mirror

Language：English  

Country：Other  

Development of Over MW Gyrotrons for Fusion at Frequencis from 14 GHz to Sub-terahertz

Language：Japanese  

Venue：東北大学 青葉山キャンパス   Country：Other  

筑波大における大型直線装置を用いたダイバータ模擬研究の現状と将来計画

Language：Japanese  

Venue：日本 東北大学青葉山キャンパス   Country：Other  

アンテナスイッチングを用いた反射計による高温プラズマ内部アルベン波動の径方向と磁力線方向の構造計測

Language：Japanese  

Venue：東北大学 青葉山キャンパス   Country：Other  

Investigation of Plasma Behavior during ECRH Injection in the GAMMA 10 SMBI Experiments

Language：Japanese  

Venue：日本 東北大学青葉山キャンパス   Country：Other  

GAMMA10/PDXバリア部ICRFアンテナの3次元波動解析コードを用いた評価

Language：Japanese  

Venue：日本 東北大学青葉山キャンパス   Country：Other  

GAMMA10/PDXにおけるアンカー部ICRFアンテナを用いた端損失プラズマ制御実験

Language：Japanese  

Venue：日本 東北大学青葉山キャンパス   Country：Other  

GAMMA 10極小磁場部における反射計を用いた高周波揺動計測

Language：Japanese  

Venue：日本 東北大学青葉山キャンパス   Country：Other  

D-D反応生成ヘリウム3に起因したイオンサイクロトロン放射のトロイダル波数と励起

Language：Japanese  

Venue：日本 核融合科学研究所   Country：Other  

アンテナスイッチングを用いた反射計による多点 ICRF波動計測

Language：Japanese  

Venue：日本 量子科学技術研究開発機構 那珂核融合研究所   Country：Other  

JT-60Uにおけるイオンサイクロトロン放射を駆動する高速イオンの速度分布解析

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：1

Type：Academic society, research group, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：3

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：3

Type：Competition, symposium, etc. 

Type：Peer review 

Proceedings of International Conference Number of peer-reviewed papers：2

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：1

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：1

Type：Competition, symposium, etc. 

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：1

Proceedings of International Conference Number of peer-reviewed papers：1

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：1

Type：Peer review 

Number of peer-reviewed articles in foreign language journals：1