High power ICRF heating experiments on the JIPP T-IIU tokamak

Abstract

In the JIPP T-IIU tokamak, a high power ICRF heating experiment has been conducted, up to an extremely high power density (∼2 MW·m−3), with a total RF power of PRF = 2 MW. Great attention has initially been paid to the problem of impurities, and it has been found that (a) the adoption of low Z materials for the limiter, (b) in situ carbon coating (i.e. carbonization) and (c) adequate gas puffing synchronized to the RF pulse are very effective in suppressing radiation loss. With these methods, a remarkable reduction in metal impurities (especially in iron impurity) has been achieved; the total radiation loss has been reduced to less than 30-40% of the input power. In these reduced radiation loss plasmas, the characteristics of ICRF heated plasmas have been studied intensively. With an increase in the ICRF heating power, a deterioration of the energy confinement time has been observed, indicating quantitative agreement with the Kaye-Goldston L-mode scaling. It is shown that the so-called profile consistency, which is the leading feature in neutral beam heated plasmas, also holds in ICRF heated plasma. It has been observed that the electron temperature profile only responds to the safety factor q(a) and does not change when the deposition profile is controlled by tailoring the k1 spectrum.

Perpendicular Ferromagnetic-Resonance Equations Derived by Effective Demagnetizing Factors

“…Two high field side launch antennas, located in adjacent ports, with power handling capabilities of about 400 kW each, were used to inject RF power at 40 MHz. Electron heating in the ion-ion hybrid regime (or mode conversion regime) on JIPP T-IIU using the 40 MHz system has been documented in previous publications [13][14][15][16]. The 40 MHz system was used in the present experiments for comparison.…”

Limiter H-mode and other improved confinement regimes with ICRF and NBI heating in JIPP T-IIU

“…Figure 2 shows a typical H-mode shot obtained with ICRF heating, with a toroidal magnetic field B, of -2 . 8 6 T, a plasma current I p of -2 2 3 kA and Hg -5 x 10 13 cm" 3 . Figure 3 shows these data on an expanded time-scale.…”

“…High power heating experiments in the ion cyclotron range of frequencies (ICRF) conducted up to 1986 on JIPP T-IIU were reported previously [1][2][3][4][5]. In worldwide attempts to establish ICRF heating as a reliable heating method, major efforts were directed towards solving the impurity problems [1,3,4]. It was also attempted to improve the heating efficiency by means of tailoring k B , the wave number parallel to the magnetic field [5].…”

“…It was also attempted to improve the heating efficiency by means of tailoring k B , the wave number parallel to the magnetic field [5]. An ICRF power of 2 MW was injected in JIPP T-IIU and a heating power density of 2 MW-m' 3 was achieved [1]. Severe degradation of the energy confinement was found to be the main feature of such intensely heated plasmas [2], as it is in plasmas heated by neutral beam injection (NBI) [6] (L-mode).…”

“…Severe degradation of the energy confinement was found to be the main feature of such intensely heated plasmas [2], as it is in plasmas heated by neutral beam injection (NBI) [6] (L-mode). The main subject of research in 1986 was a detailed study of confinement scaling and of the related profile consistency; analyses of these data were reported in 1987 [2,3].…”