• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.317-317
• /
• 2011

Enhanced ICRF (Ion Cyclotron Range of Frequency) ion heating of H-mode D(H) plasma will be tried in 2011 KSTAR experimental campaign. Minority heating is a main ion heating scheme in the ICRF. Its efficiency increases as the hydrogen minority ratio increases in deuterium plasmas. And it should be sustained at a lower level than the critical minority ratio. Consequently, it is important to elevate the critical ratio to maximize ion heating and it is possible by increasing the ion temperature or parallel wave number (k${\parallel}$) of the antenna. Increasing the k${\parallel}$ is not a good approach since the coupling efficiency decreases exponentially with regard to k${\parallel}$ as well. So the remaining method is to increase ion temperature by using NB (Neutral Beam). Ion heating fraction of NB increases as the electron temperature increases. Therefore, we will try to heat electron by using ECH together with NB ion heating before ICRF power injection. The ICRF heating efficiency will be compared with respect to several NB+ECH+ICRF heating combinations through several diagnostics such as XICS (Xray Imaging Crystal Spectroscopy), CES (Charge Exchange Spectroscopy) and neutron measurement. The theoretical background and the experimental results will be presented in more detail in the conference.

• Nuclear Engineering and Technology
• /
• v.41 no.6
• /
• pp.807-812
• /
• 2009

An ICRF discharge cleaning and a fast wave electron heating experiment were performed. For automated operation and providing the diagnostics of the ICRF system, the ICRF local network was designed and implemented. This internal network provides monitoring, RF protection, remote control, and RF diagnostics. All the functions of the control system were realized by customized DSP units. The DSP units were tied by a local network in parallel. Owing to the distributed feature of the control system, the ICRF local control system is quite flexible to maintain. Developing the subsystem is a more effective approach compared to developing a large controller that governs the entire system. During the first experimental campaign of the KSTAR tokamak, the control system operated as expected without any major problems that would affect the tokamak operation. The transmitter was protected from harmful over-voltage events through reliable operation of the system.

• Nuclear Engineering and Technology
• /
• v.56 no.1
• /
• pp.216-221
• /
• 2024

Ion cyclotron range of frequency (ICRF) heating system is an important auxiliary heating method in the experimental Advanced Superconducting Tokamak (EAST). In EAST, several megawatts of power are transmitted with coaxial transmission lines and coupled to the plasma. For the long pulse and high power operation of the ICRF waves heating system, it is very important to effectively control the power and initial phase of the ICRF signals. In this paper, a power and phase feedback control system is described based on field programmable gate array (FPGA) devices, which can realize complicated algorithms with the advantages of fast running and high reliability. The transmitted power and antenna phase are measured by a power and phase detector and digitized. The power and phase feedback control algorithms is designed to achieve the target power and antenna phase. The power feedback control system was tested on a dummy load and during plasma experiments. Test results confirm that the feedback control system can precisely control ICRF power and antenna phase and is robust during plasma variations.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.05b
• /
• pp.583-588
• /
• 1997

For the efficient current drive, the structure of ICRF wave propagation and absorption in a tokamak plasma should be first investigated. In this paper, two dimensional study on FWCD as well as ICRF minority ion heating for the KSTAR [Korea Superconducting Tok Amak Research] [1] plasma was performed using the full wave code of TORIC [2]. The ICRF wave propagation and absorption structures, the competitive power absorption between electrons and ions and the coupling of antenna/plasma are investigated.

• Proceedings of the Korean Nuclear Society Conference
• /
• 2003.10a
• /
• pp.243.1-243.1
• /
• 2003

• Nuclear Engineering and Technology
• /
• v.54 no.1
• /
• pp.207-219
• /
• 2022

The suppression of high-intensity blob structures in the scrape-off layer (SOL) by ion-cyclotron range of frequencies (ICRF) power, leading to a decrease in the turbulent fluctuation level, is observed first in the Experimental Advanced Superconducting Tokamak (EAST) experiment. This suppression effect from ICRF power injection is global in the whole SOL at EAST, i.e. blob structures both in the regions that are magnetically connected to the active ICRF launcher and in the regions that are not connected to the active ICRF launcher could be suppressed by ICRF power. However, more ICRF power is required to reach the full blob structure suppression effect in the regions that are magnetically unconnected to the active launcher than in the regions that are magnetically connected to the active launcher. Studies show that a possible reason for the blob suppression could be the enhanced E_r × B shear flow in the SOL, which is supported by the shaper radial gradient in the floating potential profiles sensed by the divertor probe arrays with increasing ICRF power. The local RF wave power unabsorbed by the core plasma is responsible for the modification of potential profiles in the SOL regions.

• Nuclear Engineering and Technology
• /
• v.54 no.10
• /
• pp.3724-3731
• /
• 2022

It is important for an ICRF full wave code to simulate the SOL (Scrape Off Layer) plasma as well as the core inside of the LCFS (Last Closed Flux Surface) for the precise prediction of the coupling between the antenna and the core plasma in tokamaks. To this end, a two dimensional full wave code based on a Fourier spectral algorithm has been developed. The spectral algorithm and procedures are described and the simulation results for the minority heating in KSTAR are reported including electric field, power absorption and power flux.

• Nuclear Engineering and Technology
• /
• v.55 no.2
• /
• pp.595-602
• /
• 2023

The EAST ICRF system operating space has been extended in power and phase control with a low-level RF system for the new double-strap antenna. Then the multi-step power and periodic phase scanning experiment were conducted in L-mode plasma, respectively. In the power scanning experiment, the stored energy, radiation power, plasma impedance and the antenna's temperature all have positive responses during the short ramp-ups of P_L;ICRF. The core ion temperature increased from 1 keV to 1.5 keV and the core heating area expanded from |Z| ≤ 5 cm to |Z| ≤ 10 cm during the injection of ICRF waves. In the phasing scanning experiment, in addition to the same conclusions as the previous relatively phasing scanning experiment, the superposition effect of the fluctuation of stored energy, radiation power and neutron yield caused by phasing change with dual antenna, resulting in the amplitude and phase shift, was also observed. The active control of RF output facilitates the precise control of plasma profiles and greatly benefits future experimental exploration.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05b
• /
• pp.935-940
• /
• 1998

The Korea Superconducting Tokamak Research (KSTAR) tokamak will have 6 MW of radio-frequency (rf) heating in the ion cyclotron range of frequencies (ICRF). The response of the antenna to the heat loads is analyzed and the resulting stresses in the Faraday shield during the normal operation is calculated. Various heat loading conditions including in the analyzes are the heat loads from the plasma, the ripple-trapped beam particles and the rf loss.

• Nuclear Engineering and Technology
• /
• v.33 no.2
• /
• pp.201-208
• /
• 2001

The high power RF transmission line components are required for transmitting MW level RF power continuously in RF heating and current drive system which heat the plasma and produce plasma current in fusion reactor The liquid stub and phase shifter is proposed as the superior to the conventional stub and phase shifter. Experimental results show that they are reliable and easy to operate compared to the conventional stub and phase shifter. There is no distortion of reflected power during the raising of the liquid level. RF breakdown voltage is over 40kV. Temperature increment of the liquid is expected not to be severe. These results verify that the liquid stub and phase shifter can be used reliably in the high power continuous RF facilities.