Previous work in the translation, confinement, and sustainment upgrade ͑TCSU͒ device ͓H. Y. Guo et al., Phys. Plasmas 15, 056101 ͑2008͔͒ demonstrated improved plasma parameters; higher temperature, higher poloidal magnetic field, increased current drive, and increased energy confinement, for rotating magnetic field ͑RMF͒ driven field reversed configurations ͑FRC͒ relative to the earlier TCS device. This was accomplished by improving vacuum conditions and using moderate wall heating ͑ϳ100°C͒ and glow discharge cleaning for wall conditioning. Two new wall conditioning techniques, siliconization and titanium gettering, have been employed to further reduce impurities and control recycling. Both techniques reduced oxygen line radiation by an order of magnitude, and total radiated power by 50%, but led to little change in overall FRC performance, reinforcing the earlier conclusion that TCSU FRCs are not radiation dominated. Titanium gettering substantially reduced deuterium recycling, requiring a new method of fueling to be developed. This is the first time a FRC has been operated without using wall recycling as the primary method of fueling. The low-recycling FRCs, maintained by enhanced puff fueling, performed similarly to standard recycling fueled FRCs in terms of a key current drive parameter B e / B , the ratio of maximum sustained poloidal field to applied RMF field, but better density control allowed for higher temperatures.
Aluminum-induced crystallization (AIC) experiments were carried out in order to investigate the influence of vacuum annealing of the Al layer at 500 8C prior to deposition of e-beam evaporated amorphous silicon (a-Si). A control sample set using the identical deposition sequences but without the Al vacuum anneal was also produced as reference. Analysis revealed that after vacuum annealing, the Al grain size increases significantly. The surface Aloxide layer thickness is reduced, however, the Al-oxide to metallic Al ratio is increased in this layer. Following a-Si deposition, the a-Si/Al/SiN x /glass stacked samples were annealed in N 2 atmosphere at temperatures between 420 and 450 8C. It was seen that the crystal growth rate in the samples with vacuum-annealed Al is significantly reduced compared to the control samples, due to the reduction of Al grain boundary density.
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