| The effect of magnetic field on the characteristics of high-intensity pulsed ion source is investigated on the magnetically insulated mode of external-magnetic field magnetically insulated ion diode (MID) in a TEMP-6 type high-intensity pulsed ion beam (HIPIB) apparatus. Without magnetic field, the parameter of magnetically insulation, perveance P, increases rapidly after the plasma production in the ion diode, indicating the short of the diode and no output of HIPIB caused by the plasma fast moving in the diode. As the magnetic field increases from 1.1 Bcrit to 1.7 Bcrit , the perveance P increases slowly, and the diode current decreases with increasing ion current density, extracted ion current and production efficiency of ion beam due to the efficiently suppressed plasma flow in the diode. The perveance P increases more slowly with the magnetic field increasing to 2 Bcrit and the ion current density falls with the decreased diode current and the decreased extracted ion current, whereas the production efficiency of ion beam is similar to that of 1.7 Bcrit caused by excessively inhibited flow of the plasma in the diode. The magnetic field of 1.7 Bcrit of the external-magnetic field MID in the TEMP-6 type HIPIB apparatus leads to the most efficient output of HIPIB with ion current density of about 350 A/cm2, diode cunent of 37 kA, extracted ion current of 11 kA, and the production efficiency of ion beam of about 30% at a peak pulse voltage of 420 kV and an accelerating voltage of 350 kV with a pulse width of 70 ns (full width at half maximum) for surface modification of materials.Thermal barrier coatings (TBCs) consist of an electron-beam physical-vapor deposited (EB-PVD) NiCoCrAlY bond coat and 7 wt.% yttria partially stabilized zirconia (YPSZ) top coat with a tetragonal phase. The YPSZ top coat shows a columnar grains forming dense clusters with gaps among grain clusters. The roughness of the as-deposited ceramic top coat is relatively low, but some spots of prominent growth defects can be observed. Such defect is a bundle of zirconia columns. After the TBCs irradiated by high-intensity pulsed ion beam, the typical remelted layer surface of the TBCs with smoothing surface appear and at the same time the characteristics of the columnar grainsdisappear with no phase change. The gaps on the top coat is filled with remelted layer, sealing top coat with the thickness of micrometer. Less severe inner oxidation of the bond coat of the irradiated TBCs is observed in many locations, where less oxidation products extended into the bond coat, and about 12 wt.% less oxygen in the thermal growth oxide (TGO) than that of the as-deposited TBCs after cyclic oxidation at 1050 °C X1 h. The observation results are consistent with the result that the oxidation rate of the irradiated TBCs is lower than that of the as-deposited TBCs from the cyclic oxidation curves at 1050 °C X1 h. It is found that the oxygen can difficultly diffuse through the sealing top coat irradiated by HIPIB, causing that the oxidation resistance of the irradiated TBCs is better than that of the as-deposited TBCs due to the decrease of oxygen activity near the interface between the top coat and the bond coat.
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