The burn characteristics are examined of an inertially confined advanced fuel pellet ignited by D-T burn, i.e. a D-T ignitor/D-D fuel and a D-T ignitor/D-3 He fuel pellet. With the help of numerical simulations of a bare target model, conditions are derived for the pellet compression needed in an advanced fuel fusion reactor. It is found that a D-T/D-D pellet having a total pR value of ~ 13 g-cm" 2 and an ignitor with a pR of ~ 5 g-cm" 2 is required for a reactor operating without tritium breeding blanket. A scaling chart of the fuel burnup and the internal tritium breeding ratio is given, and a condition to be imposed on the ignitor for efficient burn is discussed.

The suppression behaviour of magnetic island growth using electron cyclotron heating and lower hybrid current drive is analysed. A quasi-linear model is developed for island suppression, including the local peaking effect of the resistivity and the RF-driven current within the island. Pulsed launching of lower hybrid waves synchronized with the plasma diamagnetic rotation frequency can strongly suppress the magnetic island.

Emphases in recent JT-60 experiments are placed on 1)lower-hybrid (LH) current drive characteristics with a multi-junction type launcher and 2 ) the confinement study with combination of neutral beam injection, LH current drive and pellet injection. The new multi-junction LH launcher provides a 2 . 7 x 1 0 1 9 m -3 and Ip=1-1.7 MA.Volt-sec saving of -2volt-sec was demonstrated by 2 sec long, 1.6MW LHCD during the plasma current ramp of 0.4MA/s.A broad radial distribution of high energy electron current and -30% reduction in sawtooth inversion radius were obtained by high N I I (-2.5) LH injection. In order to fully suppress the sawtooth activity, low NII (-1.3) injection was found to be more effective, in which up to 1.8 sec sawtooth-free phase was obtained by 2MW LHCD for lOMW NB heating of Ip=I.SMA discharge, Improved energy confinement has been obtained with hydrogen pellet injection. Energy confinement time was enhanced up to 40% relative to usual gas fuelled discharges. The discharge has a strongly peaked electron density profile with ne(O)/-5 and n e ( 0 ) -2 . 0 ~ 1020,-3,The improved discharges are characterized by a strongly peaked pressure profile within the q=l magnetic surface, and degrades when a large sawtooth recovers or the pressure gradient may reach a critical value. When large (3mm,4mm) and fast (2.2km/s) pellets were injected, 30% energy confinement improvement was obtained even during the NB heating of 14MW. Further investigations of IDC characteristics have been made.The oxygen impurity lines from the main plasma and the main radiative loss drop first. Then the plasma stored energy starts to rise. The particle recycling is reduced around the main plasma, and is localized in the neighborhood of the X-point with a time lag of -0.2 sec. Eventually the discharge shows a significant remote radiative cooling power at the divertor region. Most of the IDC characteristics is totally different from that of H-mode, although there are some similarities i.e., gas puff degrades the confinement, both have the same favorable BT direction.

From June to October 1987, JT-60 achieved fusion product(ne(0) .r~*.Ti(Oj ) of 6 ~1 0 ' ~ m 3 . k e V . s with hydrogen plasma at plasma current of 2.8 to 3.1 MA with neutral beam power of -20 MW. The central electron density of 1 . 3 ~1 0 2 0 m-3 was obtained at plasma current of 3 MA with 13-20 MW neutral beam power and the confinement time reached 0.14-0.18 s. It is found that an offset linear scaling law like the Shimomura-Odajima scaling on confinement time will be able to reproduce experimental data better than that of the Goldston type scaling. With low beam energy injection, -40 keV, confinement degradation was found. Many short periods (0.05-0.1 s) of H-mode phase were found in outside X-point divertor discharges with NB or NB+RF(LH or IC) heating power above 16 MW. However, improvement in energy confinement time was limited to 10 %. The ballooning/interchange stability analysis were JT-60 TEAM also made for the outside X-point divertor equilibrium in connection with H-phase capability. Heating power of 9.5 MW and 1.9 MW was obtained by LHRF, ICRF injection, respectively. In combined LHRF and NB heating, the incremental energy confinement time of 0.064 s was obtained, which is the same level of that of NB heating only. In combined NB and on-axis ICRF heating of low ne discharge, an incremental energy confinement time of 0.21 s was obtained, which is three times as long as those of NB or ICRF heating only. It was also observed that high energy beam ions were accelerated by ICRF in the central region of the plasma.

Recent lower hybrid current drive(LHCD), and heating(LHH) experiments on JT-60 are reported. The current drive product of KeRpI~p -12.5~10~~m-*MA was achieved at the LH power of -4.5MW, and the CD efficiency, the energy confinement, the global power balance and the heat load on divertor plates were investigated in high power LHCD plasmas. Nearly steady state H-mode discharges were found during LHCD with two different frequency injections. Sawtooth suppression in NB heated plasmas by LHCD have shown an improvement in confinement near the plasma center. Parametric instabilities in LH heating experiments were significantly reduced by increasing the plasma current, and the stored energy increased linearly with heating power of up to -9MW at iTe -7 ~1 0 ? ~m -~ and Ip = 2.75MA. Parametric instabilities near the plasma edge in the ion heating regime were also reduced in peaked density plasmas produced by pellet injection, and LH waves increased the central plasma pressure at n,(O) > 1.4 x 1020m-3.