A new theoretical model for ozone generation from air is proposed. This model considers the dependency of the ozone dissociation rate by electron impact on the electric field strength, in addition to ozone decomposition processes through the reactions with nitrogen oxides. Assuming a stationary and uniform discharge in time and space, ozone concentrations obtained experimentally under various discharge gap widths and gas pressures are in good agreement with the analytical results. It is concluded that the discharge condition of a narrow gap and accordingly an optimized high gas pressure is one of the most effective means of efficient ozone generation for an air-fed ozone generator.

Experimental and theoretical investigations have been carried out on the ozone generation characteristics of oxygen-fed ozone generators with various discharge gap lengths. In this paper, a new theoretical model considering the dependence of ozone dissociation rate by electron impact on the electric field strength is suggested. Assuming a stationary and uniform discharge in time and space, ozone concentrations obtained experimentally under various discharge power densities and gas pressures are well explained by this model. It is concluded that the operation under a high electric field has a potential advantage in producing high-concentration ozone efficiently because of the reduction in the population density of low-energy electrons which decompose generated ozone.

Abstract:We demonstrate for the first time a 10-user, truly-asynchronous, gigabit OCDMA experiment over 50 km transmission using 511-chip SSFBG encoder/decoder and supercontinuum -based optical thresholder. Suppression of both beat noise and MAI are keys to the success. Introduction The passive optical network (PON) is promising for FTTH systems. Optical code division multiple access (OCDMA) is one promising candidate for next-generation broadband multiple access technique attributing to full asynchronous transmission, low latency access as well as soft capacity on demand [1][2][3][4][5][6][7]. There are several different OCDMA implementations that could be roughly classified according to operation principle as incoherent and coherent OCDMA [1]. Recently, coherent OCDMA using ultra-short optical pulse is receiving increasing attention with the progress of reliable and compact encoder/decoder devices, such as spatial light phase modulator (SLPM), planar lightwave circuit (PLC) and superstructured fiber Bragg grating (SSFBG). In coherent OCDMA, encoding and decoding are based on optical field amplitude instead of power intensity. The coding can be either direct time-spreading the ultra-short optical pulse using PLC [2] and SSFBG [7][8] or spectral phase-encoded timespreading using SLPM [3][4][5][6].In a common multi-user OCDMA network, multiple access interference (MAI) noise is the main issue [1][2][3][4][5][6][7]. The MAI could be suppressed effectively by employing time gating [2] or optical thresholding techniques [3][4][5][6]. Recently, multi-user coherent OCDMA experiments have been demonstrated by utilizing optical thresholding based on second harmonic generation (SHG) in periodically-poled lithium niobate (PPLN) [3,4] and nonlinear effect in high nonlinear fiber (HNLF) [5,6] to significantly suppress the MAI noise.However, coherent OCDMA could suffer from severe signal-interference (SI) beat noise if the signal and interferences overlap each other. The SI beat noise, which dominates over the MAI noise in such system, eventually limits the maximum number of active users that can be supported in the network [1]. Unfortunately, the SI beat noise could not be suppressed effectively by optical thresholding as it accompanies with the recovered signal pulse. Therefore, either slot-level [3,[6][7] or chip-level [4-6] timing coordination has been applied in previous experiments to enable multi-user transmission. Slot-level coordination is a rough synchronous approach that the signal and interferences are intentionally separated in time, therefore no beat noise will arise. Chip-level coordination is a precise synchronous approach that the signal and each interference have to be precisely aligned on a chip-level with zero interference to mitigate the beat noise. Both of them are synchronous approaches that sacrifice the most desired characteristic of OCDMA: "asynchronism". Besides, the former one significantly lowers the frequency efficiency of the system, while the latter one requires very strict network synchroniza...

30-cm-class long plasmas were generated using 2.45-GHz microwave slot antennas on a rectangular waveguide with a T-shaped ridge for the development of high performance ion sources or for plasma reactors for large-area material processing. The microwave coupling efficiencies above 85% were achieved for Ar, N2, and O2 over large flow rate ranges. From the electric fields on the inner wall E side of the waveguide, standing waves with the maximum electric field strength of about 30 kV/m were expected to be excited in the waveguide, depending on the location of the T-shaped ridge. The plasma density for Ar was in the order of 1017 m−3 and for N2 and O2 1016 m−3 in a discharge chamber in front of the slot antennas. The electron temperature for Ar ranged from 3 to 4 eV and for N2 and O2 from 3 to 8 eV. The spatial profiles of the ion saturation current for Ar were almost flat in the discharge chamber although the profiles for N2 and O2, with large flow rates or near the antennas, were slightly rough.

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