The H mode was achieved in limiter discharges of a tokamak with lower-hybrid current drive for the first time. Simultaneous application of rf powers at two different frequencies such as 1.74 and 2.23 GHz or 1.74 and 2.0 GHz appeared to be effective in the attainment of the H mode. The threshold lowerhybrid power was as low as the Ohmic-heating power with hydrogen plasmas. A nearly steady-state edge-localized-mode-free H mode with a duration up to 3.3 sec was established without significant impurity accumulation.PACS numbers: 52.55.Fa, 52.35.Hr, 52.55.Pi Since the discovery of a phase of improved confinement during neutral-beam-injection (NBI) heating, known as the H mode, in the poloidal divertor configuration of ASDEX, x the H mode has been obtained with several heating schemes such as ioncyclotron-resonance heating (ICRH), 2 " 4 a combination of NBI and electron-cyclotron heating (ECH), 5 ECH, 6 7 and Ohmic heating alone. 8 The H mode has also been realized in limiter discharges. 3,9,10 This Letter reports the first observation of the H mode in limiter discharges with lower-hybrid current drive (LHCD). We observed sharp L-to-H and H-to-L transitions in distinction from the particle-confinement improvement during LHCD in Versator II. 11 The threshold LH power of the //-mode transition was about 1.2 MW with hydrogen plasmas.In JT-60, the H mode was obtained in the outer or lower divertor configuration with NBI heating and combined heating with NBI and ICRH or NBI and LH. 12 The threshold heating power was about 16 MW. In contrast to the beam-heated H mode with frequent edge localized modes (ELM) in the divertor configuration, the limiter H mode with LHCD produced ELM-free H phases longer than 3 sec.Typical plasmas of the present experiments had R =3.04 m, a =0.89 m, and nearly circular cross section which contacted inner bumper-type limiters. The gap between the outermost flux surface and the outside limiters was about 5 cm. Graphite first walls were conditioned by Taylor-type discharge cleaning. The plasma was developed from hydrogen gas at B t =4.5 T, and the plasma current was 1.5 MA resulting in ^Sur~4.7. The LH power was applied from two launchers; a conventional grill of 8 (torroidal) x 4 (poloidal) and a multijunction type of 24x4 phased-array wave guides. ,3,14 The launchers were located at the outer (low field) side of the torus at an upward angle of 40° from the midplane. Most of the experiments were conducted with LH waves at two different frequencies of 1.74 and 2.23 GHz from the multijunction and conventional launchers, respectively. The phase differences between adjacent wave guides were 180° and 90°, the phasing of which provides high directivity for current drive. The peaks of the refractive index parallel to the magnetic field were about 2.1 and 1.5, respectively.Typical traces of an //-mode discharge with LHCD are shown in Fig. 1. The LH power of about 1.4 MW was launched for 3 sec. The gas feed was turned off just E11295 4 5 6 7 8 9 t (sec)FIG. 1. Time evolution of plasma stored energy eva...