Overview of KSTAR initial operation

Abstract

Since the successful first plasma generation in the middle of 2008, three experimental campaigns were successfully made for the KSTAR device, accompanied with a necessary upgrade in the power supply, heating, wall-conditioning and diagnostic systems. KSTAR was operated with the toroidal magnetic field up to 3.6 T and the circular and shaped plasmas with current up to 700 kA and pulse length of 7 s, have been achieved with limited capacity of PF magnet power supplies. The mission of the KSTAR experimental program is to achieve steady-state operations with high performance plasmas relevant to ITER and future reactors. The first phase (2008–2012) of operation of KSTAR is dedicated to the development of operational capabilities for a super-conducting device with relatively short pulse. Development of start-up scenario for a super-conducting tokamak and the understanding of magnetic field errors on start-up are one of the important issues to be resolved. Some specific operation techniques for a super-conducting device are also developed and tested. The second harmonic pre-ionization with 84 and 110 GHz gyrotrons is an example. Various parameters have been scanned to optimize the pre-ionization. Another example is the ICRF wall conditioning (ICWC), which was routinely applied during the shot to shot interval. The plasma operation window has been extended in terms of plasma beta and stability boundary. The achievement of high confinement mode was made in the last campaign with the first neutral beam injector and good wall conditioning. Plasma control has been applied in shape and position control and now a preliminary kinetic control scheme is being applied including plasma current and density. Advanced control schemes will be developed and tested in future operations including active profiles, heating and current drives and control coil-driven magnetic perturbation.

E×Bshear suppression of turbulence in diverted H-mode plasmas: role of edge magnetic shear

“…That work [4] also acknowledges an importance of enhanced edge magnetic shear produced by the current ramp down. KSTAR tokamak has achieved H-mode plasmas well ahead of its original schedule [5]. An interesting feature of KSTAR plasmas at the H-mode transition is an abrupt increase in its edge q value and elongation [6].…”

Implementation of a Novel Real-Time Controller for the Detection and Tracking of Magneto-Hydrodynamic Instabilities on the JET Tokamak

“…The very different magnetic geometry and the different spectral boundary conditions, namely the presence of an additional quantum number for the mode (radial mode number) to the two in tokamaks (toroidal, poloidal), and the absence of a generalized toroidal symmetry, make the efficient application of a Sparse Representation method, such as the SparSpec code, a very challenging problem. Newer tokamak devices such as KSTAR [32] and HL-2A [33] could also benefit in their next phase of operations from active suppression of multi-harmonics MHD modes with reliable actuators as simulations may not be able to provide on their own all the required control answers. The experience acquired at JET with the AELM and the SparSpec code may then be used to prepare and test offline dedicated control systems.…”

Plasma density measurements using THz pulses from laser-plasmas

“…In the experiment, the Ti:Sapphire regenerative amplifier laser system (Spectra-Physics Spitfire Pro) in our laboratory was used, which can provide p-polarized laser pulses with a central wavelength of 795 nm, an energy of 1 mJ/pulse, 40 fs pulse duration, and 1 kHz repetition rate. For this experiment, the ICP chamber was specially designed to yield electron densities similar to that of fusion reactors such as KSTAR (Korea Superconducting Tokamak Advanced Reactor) [13]. The ICP was operated using the 13.56 MHz radiofrequency (RF) power source with an impedance matching network (RFPT Co. Ltd.).…”