Gas puff imaging (GPI) offers a direct and effective diagnostic to measure the edge turbulence structure and velocity in the edge plasma, which closely relates to edge transport and instability in tokamaks. A dual GPI diagnostic system has been installed on the low field side on experimental advanced superconducting tokamak (EAST). The two views are up-down symmetric about the midplane and separated by a toroidal angle of 66.6°. A linear manifold with 16 holes apart by 10 mm is used to form helium gas cloud at the 130×130 mm (radial versus poloidal) objective plane. A fast camera is used to capture the light emission from the image plane with a speed up to 390,804 frames/s with 64×64 pixels and an exposure time of 2.156 μs. The spatial resolution of the system is 2 mm at the objective plane. A total amount of 200 Pa.L helium gas is puffed into the plasma edge for each GPI viewing region for about 250 ms. The new GPI diagnostic has been applied on EAST for the first time during the recent experimental campaign under various plasma conditions, including ohmic, L-mode, and type-I, and type-III ELMy H-modes. Some of these initial experimental results are also presented.
A novel optical frequency-hopping system based on distributed feedback laser integrated with an electroabsorption modulator is proposed and demonstrated. In the proposed system, a user's data are split into segments and modulated onto multiple optical frequency shift keying carries, therefore, a single wavelength of optical carrier only carries partial user's data. By this way, the security of optical communication system is improved. In this paper, we demonstrate an error free transmission through 32-km single mode fiber and 8-km dispersion compensation fiber with 2.5 Gb/s hopping rate and 10 Gb/s data rate. Meanwhile, we also compare and analyze the performance of the proposed system with different hopping rate and data rate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.