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The paper summarizes the main results ob'ahed during the f i r s t six mnths of experimental work on TEXMR w i t h ohnically heated plasmas. The machine(R = 175 cm; a = 45-50 an) was operated a t wall temperatures up t o 303 ' %2 w i t h hydrcgen gas, a toroidal field of 2 T and a maximm plasma current of 503 kA, yielding central electron temperatures of 1.2 keV, mximm line-averaged densities of 4 x 1013 an-3 and discharqe durations of up t o 2 . 7 sec (for Ip$ 340 kA). Besides providing long-lasting reproducible plasmas for forthcoming plasmawall interaction research, the following tasks were acccanplished: (1) control of low Z impsrities by effective wall cleaning and conditioninq; (2) accurate plasma positioninq for extended pulse durations;(3) determination of the current density distribution by way of Faraday rotation masurments; (4) investigation of plasma limiter interaction including spectroscopic d e t m i n a t i o n of released neutral particle fluxes and measaement of the power density distribution in the scrape-off layer by infrared-thermography.

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Experimental investigation of the transparent cathode used in a relativistic magnetron with axial radiation is reported in this paper. The transparent cathode is composed of six separate stalks with the diameter of 6 mm. Under the working condition of 549 kV and ∼0.38 T, the relativistic magnetron with the transparent cathode experimentally produces a 550 MW microwave. The radiation mode is TE(11) at the frequency of 2.35 GHz. The total efficiency is 16.7%. The variations of the relative positions between the separate stalks and the anode blocks can perform the maximum difference of 4 ns in microwave duration. Compared with the conventional solid cathode, the transparent cathode provides faster startup time of 12 ns, relatively wider pulse duration of 35% and relatively higher efficiency of 10.6%.

Effects of edge radial electric field Er and Er × B flow shear on edge turbulence and turbulent transport, in particular, on large-scale blobs and blobby transport have been investigated in the positive and negative biasing discharges in the J-TEXT tokamak. The results show that under certain conditions, the positive electrode biasing induces better plasma confinement than the negative biasing. Further studies reveal that in addition to flow shear effects on blob dynamics, the local radial electric field at the edge region plays a significant role in repulsion of the blobs and associated transport, leading to improvement of particle confinement when the outward motion of the blobs is blocked. The results are in accordance with theoretical predictions.