Japan-Korea Workshop on Physics and Technology of Heating and Current Drive

Contribution List

12. Development of a Lower Hybrid Fast Wave Antenna and Low Power Coupling in KSTAR Plasmas

A traveling wave antenna consisting of a slotted waveguide with corrugated walls has been developed for lower hybrid fast wave (LHFW) experiments in KSTAR plasmas [1]. n_(∥0) increases from 2.1 to 2.6 as the frequency increases from 2.4 GHz to 2.5 GHz. Plasma coupling simulations show that the coupling efficiency reaches nearly 60% and imply that controlling the gap distance to be shorter than...

8. Effect of vertical space of vacuum vessel on formation of closed flux surfaces by ECH

In the Low Aspect ratio Torus Experiment (LATE) device, non-inductive startup of spherical Tokamak by electron cyclotron wave (ECW) and/or electron Bernstein wave (EBW) using 2.45 GHz microwaves has been explored, where all the processes including breakdown, plasma current initiation and ramp-up are carried out with EC and/or EB waves.
In such EC startup of Tokamaks, initial closed flux...

16. Estimation of Electron Cyclotron Plasma Heating Profiles Based on Ray Tracing Simulation Data

Efficient plasma heating is a crucial prerequisite for achieving fusion reactions in KSTAR, where the plasma temperature must reach the order of 100 million degrees Celsius. Among various heating mechanisms, electron cyclotron heating (ECH) utilizes the electron cyclotron resonance frequency of RF waves to transfer energy directly to the electrons. However, in practical operation, the actual...

2. Hybrid simulation of Alfvén Eigenmodes due to multiple fast ions in the Large Helical Device

In the magnetic confinement fusion devices, there are multiple fast ion species such as fusion product α-particles and fast deuterons produced by neutral beam injection (NBI). These fast ions may induce instabilities such as Alfvén Eigenmodes (AEs) which enhance fast-ion transport and losses. The study of fast ion driven instabilities is one of the important topics for fusion reactor.

To...

6. Kinetic full wave analysis of electron cyclotron waves using integral form of dielectric tensor

see attached PDF file

9. Negative Ion Production Characteristics of Two-Region Arc Plasma (TRAP) Ion Source

At the Korea Atomic Energy Research Institute, a novel Two Region Arc Plasma (TRAP) ion source is under development for negative hydrogen neutral beam injection (NBI) systems in fusion applications. A key advantage of this design is its ability to confine primary electrons emitted from the filament exclusively within the driver region, thereby eliminating the need for external filter magnets....

15. Non-inductive plasma ramp-up using 8.56 GHz ECH system on QUEST

Non-inductive electron cyclotron (EC) plasma current ramp-up experiments have been conducted on the QUEST spherical tokamak [1]. A new 8.56-GHz ECH klystron system with incident-mode selectivity was developed for long-pulse sustainment and effective bulk electron heating [2].
Ray tracing calculations were used to evaluate the power absorption for core plasma heating via the fundamental...

10. Non-inductive start-up experiment with various lower-hybrid launch scenarios on TST-2

Efficient non-inductive start-up of a spherical tokamak may be achieved by using lower-hybrid waves that have high current drive efficiency. On the TST-2 spherical tokamak, three lower-hybrid launchers are installed at the outer-midplane, top and outer-off-midplane to explore efficient start-up scenarios. Plasma current ramp-up up to 26 kA has been achieved so far, which is about a quarter of...

21. Observation of non-thermal RF radiations excited during external heating

The external heating methods such as ECRH, ICRF heating, and NBI can achieve the velocity population inversion at least for a short time. With the existence of the velocity population inversion, non-thermal radiations are generated as the results of kinetic instabilities. With using of high speed digitizers, various types of precise frequency spectrograms of non-thermal radiations have been...

4. Oscillation of negative ion beamlet and effect on beam focusing for negative-NBI

Direct effect of RF electric field was identified with RF perturbation experiment on FA negative ion source. We found (1) the beamlet width and beamlet axis position oscillate with RF frequency, (2) the amplitude of beamlet width is proportional to RF electric field and to the gradient of the perveance curve d<wx>/dPerv. We also discuss about how to suppress the oscillation of the beamlet in...

1. Recent activity in dual frequency (142/208 GHz) gyrotron development and transmission line system

A dual-frequency gyrotron is currently under development at UNIST to support future DEMO-relevant and innovative fusion reactors. The target frequencies, 142 GHz and 208 GHz, have been selected based on conceptual design requirements and the availability of existing laboratory resources. The conceptual design study of the gyrotron has been completed, and experimental activities to validate the...

14. Report on the helicon current drive in KSTAR and the expected performance in Korean DEMO reactor

The plasma current drive has been an essential for the recent achievement of high performance KSTAR discharges. For the effective plasma current drive, near-parallel P-NB and EC has been routine auxiliaries in KSTAR. In addition to these conventional technologies, helicon current drive [1] has been developed to supply efficient off-axis current to the KSTAR plasmas for the development of...

20. Result of ECRH operation in the integrated commissioning phase and upgrade toward the initial research phase on JT-60SA

During the integrated commissioning phase of JT-60SA, two ECRH systems were operated at 110 GHz with a small-diameter waveguide of 31.75 mm (Unit1) and 82/110/138 GHz with a large-diameter waveguide of 60.3 mm (Unit2) [1,2]. Although the large-diameter waveguide contributes to reduce transmission loss, it potentially has a larger mode conversion loss due to misalignment compared to the...

3. Simultaneous Estimation of Edge Plasma Density Profiles and Heating Beam Properties via Bayesian Inference and Gaussian Process Regression in the KSTAR H-BES System

In this study, we develop a method for estimating edge plasma density profiles and analyzing beam attenuation using the KSTAR hydrogen beam emission spectroscopy (H-BES) system. The system, comprising 16 radial and 4 poloidal channels with approximately 1 cm spatial resolution, measures Doppler-shifted D-alpha emissions that serve as indicators of local plasma conditions. A collisional...

11. Status and recent experimental results of KSTAR NBI system

SeulChan Hong (KFE), Dr J.H. Jeong (KFE)

The KSTAR Neutral Beam Injection (NBI) system plays a crucial role in achieving high-performance, long-pulse plasma operation by providing substantial plasma heating and current drive. It consists of two beamlines, NBI-1 and NBI-2, each equipped with three positive-ion-based ion sources, designed to deliver 2.0 MW of deuterium beam power at an energy of 100 keV. In the 2024 KSTAR campaign,...

7. Status of LHD ECH system for next campaign and related topics

Electron cyclotron resonance heating (ECRH) plasmas have been crucial in various aspects of plasma physics research and fusion reactor development. They have been widely utilized for plasma start-up, allowing efficient initiation of confined plasmas and for extending plasma operation durations by maintaining stable plasma conditions. Furthermore, ECRH is essential for plasma transport studies,...

13. Study of Beam Trajectory in KSTAR Neutral Beam Injector using Beamlet-Based Model

The KSTAR Neutral Beam Injection (NBI) system utilized to achieve high-performance, long-pulse plasma operation by providing substantial plasma heating and current drive. During the beam transmission, the high-energetic NB generates thermal loads due to collisions with transmission line components and is influenced by external conditions such as magnetic field. To study the impact of external...

5. Study of Microwave Transmission Mode Content in KSTAR ECH transmission line from Measured Field Intensity

Dr Ajay Kumar Pandey (KSTAR Research Centre, KFE, Daejeon, Korea)

The study of transmission modes of electron cyclotron heating (ECH) transmission lines are very important for the long pulse operation as the gyrotron is located far away from the plasma device [1]. This mode is studied by using phase retrieval method based on intensity pattern. The pattern was measured by taking temperature profile on a paper screen which is placed at different locations and...