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ABSTRACT: Helicon plasma source is known as efficient generator of uniform and high density plasma. A helicon plasma source was developed for investigation of plasma neutralization and plasma lens in the Institute of Modern Physics in China. In this paper, the characteristics of helicon plasma have been studied by using Langmuir four-probe and a high argon plasma density up to 3.9x10(13) cm(-3) have been achieved with the Nagoya type III antenna at the conditions of the magnetic intensity of 200 G, working gas pressure of 2.8x10(-3) Pa, and rf power of 1200 W with a frequency of 27.12 MHz. In the experiment, the important phenomena have been found: for a given magnetic induction intensity, the plasma density became greater with the increase in rf power and tended to saturation, and the helicon mode appeared at the rf power between 200 and 400 W.
The Review of scientific instruments 02/2010; 81(2):02B105. · 1.52 Impact Factor
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ABSTRACT: The optical emission process of atomic hydrogen (Halpha, Hbeta, Hgamma), atomic carbon C(2p3s2p2 : lambda = 165.7 nm) and radical CH(A2delta --> X2II: lambda = 420-440 nm) in diamond film growth by electron-assisted chemical vapor deposition (EACVD) from a gas mixture of CH4 and H2 was studied by using Monte-Carlo simulation. The variation of the emission lines with gas pressure (0.1-12.5 kPa) of different substrate temperatures (573-1 173 K) was investigated. And the results show that at different substrate temperatures the intensity of all the emission lines increase with increasing gas pressure at first, whereas decreased afterward. Furthermore, the emission lines intensity decreases with increasing substrate temperature at a relative low gas pressure, while increases with increasing substrate temperature at the higher gas pressure.
Guang pu xue yu guang pu fen xi = Guang pu 04/2008; 28(4):763-5. · 0.84 Impact Factor
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ABSTRACT: The optical emission process of atomic hydrogen (Halpha, Hbeta, Hgamma), atomic carbon C(2p3s-->2p2: gamma= 165. 7 nm) and radical CH( A(2)delta--> X(2) II:gamma=420-440 nm) in diamond film growth by electron-assisted chemical vapor deposition (EACVD) from a gas mixture of CH4 and H2 was studied using Monte-Carlo simulation. Spatial distributions of the emission lines were investigated. The spatial distributions of intensity of all these emission lines were the same on the whole, which increases with the distance from the filament and decreases near the substrate. The intensity of atomic hydrogen lines decreases with increasing CH4 concentration, while that of CH and atomic C lines increases with increasing CH4 concentration.
Guang pu xue yu guang pu fen xi = Guang pu 02/2007; 27(1):15-7. · 0.84 Impact Factor
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ABSTRACT: The process of atomic hydrogen emission in the CH4/H2 gas mixture in EACVD was simulated by Monte Carlo method. In the simulation the collision between electron and H2 molecule has two basic types: elastic collision and inelastic collision. Four types of inelastic processes have been considered, namely vibrational excitation, dissociation, electron excitations and ionization. For e-CH4 collision, elastic momentum transfer, vibrational excitation, dissociation, ionization, and dissociation ionization were considered. The relationship between the numbers of H, and CH3, and the atomic hydrogen emission line intensity under different experimental conditions was investigated. A method of extrapolating the optimum experimental condition for diamond deposition by the atomic hydrogen emission line is given. The result is of great importance to depositing high quality diamond films by controlling the conditions of technology efficiently.
Guang pu xue yu guang pu fen xi = Guang pu 11/2005; 25(10):1545-7. · 0.84 Impact Factor
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ABSTRACT: The process of atomic hydrogen emission in CH4/H2 gas mixture in EACVD is simulated by Monte Carlo method. In the simulation two basic types of collision between electron and H2 molecule are considered: elastic collision and inelastic collision. Four types of inelastic processes have been considered, namely vibrational excitation, dissociation, electron excitation (contains Halpha, Hbeta and Hgamma) and ionization. For e-CH4 collision, elastic momentum transfer, vibrational excitation, dissociation, dissociative excitation (contains Halpha, Hbeta and Hgamma), ionization and dissociative ionization are considered. The relationship between the number of H, CH3 and the ratio of atomic hydrogen emission line intensity under different experimental conditions is investigated. A method to obtain the optimum experimental condition for diamond deposition by the atomic hydrogen emission line is given. The result is of great importance to depositing high quality diamond films by controlling the conditions of technology efficiently.
Guang pu xue yu guang pu fen xi = Guang pu 07/2005; 25(6):801-3. · 0.84 Impact Factor
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ABSTRACT: The process of atomic hydrogen emission in CH4/H2 gas mixture in EACVD is simulated by Monte Carlo method. In the simulation the collision between electron and H2 molecule has two basic types: elastic collision and inelastic collision. Four types of inelastic processes have been considered, namely vibrational excitation, dissociation, electron excitation and ionization. For e-CH4 collision, elastic momentum transfer, vibrational excitation, dissociation, ionization and dissociation ionization are considered. The relationship between the ratio of atomic hydrogen emission line intensity and mean temperature of electron under different CH4 concentration in the gas mixture is investigated. A method of determining the mean temperature of electron in situ in the process of diamond film deposited by EACVD is given. The result is of great importance to depositing high quality diamond films by controlling the conditions of technology efficiently.
Guang pu xue yu guang pu fen xi = Guang pu 05/2005; 25(4):494-6. · 0.84 Impact Factor
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ABSTRACT: Gibbs sampler, a typical Markov chain Monte Carlo (MCMC) method that approximately solves the Bayesian problem by simple numerical computation in a completely different paradigm was previously employed for the Bayesian detection in synchronous CDMA system. To perform the Bayesian detection for the asynchronous uplink CDMA system with unknown multiuser interference and multipath fading, the Gibbs sampler combined with the linear group-blind decorrelator is proposed as a novel Bayesian multiuser detection technique in this paper. Furthermore, in the study of the effect of channel estimation error on the performance of the proposed detector, we also present an iterative Bayesian multiuser detector where more accurate parameter estimation is achieved to improve the detection performance. Simulation results verify the effectiveness of the proposed detectors. The proposed detection techniques have the advantages of low complexity, high performance and wide applications.
Communications, 2003. ICC '03. IEEE International Conference on; 06/2003
