Tong Linsu

Study of the emission performance of carbon nanotubes

The carbon nanotube has good field emission properties, so it has been used as the electron source on the field emission display panel. To obtain a high emission current, the electric field at the tip of the nanotube must be large enough. This article studies the variation of electric field with different types of nanotubes. The emission current of the nanotube is also calculated for various geometrical parameters of nanotubes. From the simulation results, the influence of the geometrical parameters on the emission performance of nanotubes is studied.

Calculation of aberration of electron gun in color picture tubes

Abstract In a color picture tube, aberration is an important factor influencing the electron beam spot on the screen. This paper discusses a new method which is used to calculate the aberration of an electron gun in a CPT. In this method, electron trajectories are simulated directly in the cathode and the pre-focus lens. In the main lens, the asymptotic aberration is calculated to decide the size of the image. Some results of the calculation are shown in this paper.

Optimization of a particle optical system in a mutilprocessor environment

In the design of a charged particle optical system, many geometrical and electric parameters have to be optimized to improve the performance characteristics. In every optimization cycle, the electromagnetic field and particle trajectories have to be calculated. Therefore, the optimization of a charged particle optical system is limited by the computer resources seriously. Apart from this, numerical errors of calculation may also influence the convergence of merit function. This article studies how to improve the optimization of charged particle optical systems. A new method is used to determine the gradient matrix. With this method, the accuracy of the Jacobian matrix can be improved. In this paper, the charged particle optical system is optimized with a Message Passing Interface (MPI). The electromagnetic field, particle trajectories and gradients of optimization variables are calculated on networks of workstations. Therefore, the speed of optimization has been increased largely. It is possible to design a complicated charged particle optical system with optimum quality on a MPI environment. Finally, an electron gun for a cathode ray tube has been optimized on a MPI environment to verify the method proposed in this paper.

Fuzzy optimization of an electron optical lens

Abstract In ordinary optimum methods, the geometric parameters and electric parameters are constrained in some closed intervals. From the view of engineering, the physical variables which give some definite boundaries are not strictly constrained, so this paper proposes the fuzzy optimization of an electron optical lens. In this method, the constraints of the structure parameters and the electric parameters are considered as fuzzy intervals in a real field. A fuzzy optimum set has also been obtained. A four electrodes extended field lens (4EFL) is taken as an example to be fuzzy optimized, and the curve of optimal points in the 4EFL is plotted in this paper. Because this method has taken account of the fuzzy factors, its result will fit with the practical condition properly.

A boundary integral method for calculating the field in liquid metal ion sources

Abstract A boundary integral method has been developed to calculate the space charge field in liquid metal ion sources. Some new methods are suggested in order to save computer time and memory. The numerical results have been compared with the analytical solutions of a spherical capacitor, which show a satisfactory accuracy.

A new type of combined bipole deflector for a rf glow discharge ion source

Abstract In order to reduce the disturbances produced by photo-radiation and neutral particles in a rf glow discharge ion source which is used in a sputtered neutral mass spectrometer, a new type of combined bipole deflector has been developed, which consists of half-cylindrical electrodes and diaphragms with eccentric apertures. A theoretical analysis and experiments have been carried out. It has been shown that the background of photo-radiation can be reduced by six orders of magnitude with the eccentric structure. The ion beam is extracted with double deflection and focused laterally by the half-cylindrical bipoles, which results in a high ion transmission up to 20%. This deflector is suitable for coupling a plasma type of ion source with a quadrupole mass spectrometer and has extremely high ratio of signal to noise.

Some improvements on the calculation of emission current in liquid metal ion sources

Abstract In order to improve the accuracy of the calculation of emission current in liquid metal ion sources, an iteration is introduced into the Constant Total Current method developed by Kang and Kingham, which well satisfies the self-consistency of emission current, surface field strength and space-charge effect. The calculation of current-voltage characteristic of liquid metal ion source shows a better agreement with the experiments than do previous theoretical results.