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Electron cyclotron emission (ECE) diagnostics have been developed in the Large Helical Device (LHD). The ECE is transmitted from the antenna to the spectrometer for 80 m by means of a corrugated waveguide system, which has a small transmission loss (~30%) in LHD. Although the field angle changes from-40 to +30 degrees on the sight-line of the ECE antenna, it has been observed that the polarization of ECE, which is determined at the plasma edge in LHD, is identical for all frequencies. Thus, the electron temperature profile can be measured using the second harmonic X-mode of ECE. The ECE measured by the Michelson is calibrated with a hot source in order to reduce noise. The ECE temperature measurement agrees well with the Thomson scattering measurement over a wide range of electron densities. The radiometer is cross-calibrated to the Michelson, and is employed for the study of fast phenomena such as internal transport barrier (ITB) formation. Tangentially emitted ECE, in addition to the normal ECE, is investigated in LHD in order to explore the potential of ECE diagnostics.

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Significant extensions in the TFTR plasma operating regimes have been achieved with additional heating-system capability, installation of a multishot pellet injector, and the development of an enhanced confinement regime. In ohmi^ally heated pelletfueled discharges characterized by highly peaked density profiles, enhancements in tp have resulted in n e (0)x E (a)-values of 1.5 x 10 m"^s. In neutral-beam-h.ated discharges, an operating regime has been developed in which substantial improvements in energy confinement time and neutron source strength ?re observed. Ion temperatures of -20 keV and n^OHgfajTjJoj-values of 2' x 10 20 m"^s keV have been achieved. This enhanced confinement regime is characterized by high values of 3 and low values of collisionality. The observed surface voltage, which is negative during beam injection, is compared with models including beamdriven and bootstrap currents. I.