In this paper, the coma of the fifth-order aberration at a large deflection angle has been analyzed by using multipole field theory. The dilemma effect exists in the comas of fifth-order aberration. The dilemma effect, whose value D3 is constant and independent of the 10-pole field, is the linear combination of coma aberrations. The coma of the fifth-order aberration is corrected by adjusting the 10-pole field distribution when Dr is zero or small. The factors that influence the dilemma effect have been calculated and analyzed.

In the normal gate CNT-FED, the gate electrode is used to modulate and address the electron beam. Some electrons may bombard on the gate electrode, thus the luminant efficiency of CNT-FED decreases. This paper proposes a new gate structure, which is the metal mesh with cone funnels. MgO film and MgF2 film are vaporized on the surface of the mesh and the funnels. When the primary electrons bombard on the gate electrode with initial energy, the secondary electrons and backscatters are generated. As results, more electrons can pass through the gate electrode and land on the anode. Consequently, the brightness of the novel triode structure CNT-FED can increase obviously. In the paper, we show the results of numerical simulation of the secondary electron emission process with Monte Carlo method. Some CNT-FED devices with the new type of gate structure are fabricated. The surface of the gate electrode is coated with MgO, MgF2 and SiO2 film, respectively. The results of emission experiments are also shown in this paper.

Charge accumulations on the wall of the chunnels in field emission devices are analyzed with the Monte Carlo method. The chunnel's wall is dielectric, and secondary electrons are generated when electrons hit the chunnel's wall. Under the electron bombardment, the secondary emission induces charging on the wall. It is implied that in the field emission process, the upper part of the chunnel's inside wall is positively charged, while the lower part of the chunnel's inside wall and the chunnel's underside wall are negatively charged. Four models with different forms of chunnels are studied. We analyze the effect of charge accumulation in different models by comparing the potential distributions near the cathode and the current density distributions of the cathode, respectively. The results show that increasing the slope of the chunnels will reduce charge accumulations at the chunnel's underside wall. Also, the energy distributions of electrons arriving at the anode are analyzed, and it suggests that the chunnel's slope may decrease the ratio of primary electrons directly on the anode to all the electrons on the anode.

In the design of devices containing beams of charged particles, it is helpful to know how the particle's trajectories will be modified by small displacement of electrodes. This paper describes a method to predict the perturbation of particle trajectories. In this methodology, the derivative of the potential is deduced from the results of finite element computation. The equation of motion is solved to calculate the perturbation of particle trajectories separately. An example of a perturbation trajectory in an electrostatic lens is presented.

In the application of field emitter arrays, it is useful to understand its emission performance. This paper calculates the electric field of a diode emitter array in three-dimensional space. From this calculation, the emission uniformity of a diode array is studied. The dependance of the tip-to-tip spacing and of the cathode-anode distance on the uniformity of the array is also analyzed. The pressure sensor based on the diode model is simulated. From the dependence of the emission current for different tip densities, the influence of the emission uniformity can be obtained. (1999 Published by Elsevier Science B.V. All rights reserved.