Narrow Results

Plate shape TA2 alloys were joined by vacuum electron beam welding(EBW) method. The microstructures of the joint shown that a few agglomerate β phase appear in seam zone beside dominating α phase, the heat affect and the seam zone had coarse texture compared with the base metal. Distribution of abnormal phase in the seam zone increased the local mechanical property and resulted bad corrosion resistance, because homogenous α phase has higher electric potential than abnormal phase. The tensile property of the joint shown that the joint broke at the base metal instead of the fusion zone, the fracture type shown ductile dimple fracture pattern, and the elongation of the sample is over 24% as that of the bulk titanium alloys.

The electrostatic electron Bernstein wave (EBW) can provide localised on- and off-axis heating and current drive in typically overdense (high-β) spherical tori (ST) where the usual electromagnetic EC modes are cut-off. Hence, the EBW is a candidate for plasma control and stabilisation in such devices. We present here a modelling of EBW heating and current drive in realistic ST conditions, particularly in typical NSTX equilibria and in model equilibria for NHTX [1] and MAST Upgrade [2,3]. The EBW injection parameters are varied in order to find optimized scenarios and possible ways to control the deposition location and the driven current. It is shown that EBWs can be deposited and efficiently drive current at any radial location.

The prototype phased-array antenna system has been developed to control the incident angle and polarization to conduct the Electron Bernstein Wave Heating and Current Drive (EBWH/CD) experiments on the QUEST. The two orthogonal fields measured at the low power level were in excellent agreement with those evaluated by a developed Kirchhoff code. The elliptical polarization in two orthogonal fields can be controlled to excite pure O-mode in the oblique injection. The non-inductive plasma current of 10 kA was ramped up and sustained for 0.7 s. The phased-array antenna system for the reflectometry and the EBW radiometry has been also develoloped concerning the EBWH/CD experiments, and was confirmed to work well in the low power tests.

The power deposition profiles were analyzed with a multiple ray tracing code for the Electron Bernstein Wave Heating and Current Drive (EBWH/CD) experiments in the QUEST. In the EBWH/CD experiments in the QUEST, the O-X-B mode conversion scenario was selected for the plasma current sustainment in the rather low-density case. The algorithm for the wave penetration through evanescent layer beyond a O-mode cutoff position was developed for the multiple-ray analysis. The launching antenna positions were considered to obtain the significant wave absorption in the specific propagating direction using the developed ray-tracing code.