The computation is clarified for the electron beam density modulation in optical klystron on storage ring free electron laser with three different methods,and the effects of electron beam parameters on density modulation are also studied.The numerical results show that the three dimensional simulation is necessary.

The generation of pulsed high-energy-density plasma by electromagnetic implosion of cylindrical gas shell (i.e.,hollow Z pinches)has been investigated theoretically using a one-dimensional code proposed here.The main mechanism of EM implosion process involves hydrodynamics,radiation in the collapsing plasma,and equation of LR circuit.The discrepancy between the numerically computed results and the experementally measured results is found to be less than 10%.It is shown that this code can be used as a tool to design new EM implosion device.

The theoretical analyses of the beam emittance on SG-1 FEL device have been presented in this paper. The measured beam emittance is about (0.4-0.5) rad·cm. From the experimental beam quantity and numerical simulation resalt, it appears that the quantity of beam current is good enough to abandom the 9-m-long beam modulated system, while substituting with 2-m-long drifting focusing regiou.

In this paper, the equations of FEL amplifier with aplanar wiggler are derived. FBC code based on equations is designed by H.P.Freund. WAGFEL code based on KMR theory are designed by us. Although there are obvious differences between WAGFEL and FBC code, in dealing with practical problems such as magnetic field and length of the entry wiggler, initial distribution of electron beam, fashon of the downstream tapered wiggler etc, a set of c-oupled nonlinear differential equations used in two codes is based on single-particle theory. Meanwhile, under the certain conditions, the computational results of both WAGFEL and FBC code coincide with those of the experiment well. Then the computional results used by WAGFEL and FBC code are compared.The results of TE₀₁ mode calculated with WAGFEL and FBC code are compared and analyzed under the condition of the constant and varyable amplitude of wiggler magnetic field B_w, respectively. The analyzed results show that regard the conditions and results of experiment as criterion, WAGFEL code is more useful in comparing similation results with experiment than FBC code. As a result, not only data of 4MeV amplifier which are computed by WAGFEL code are valuable, but WAGFEL code is feasible to design amplifier and study problems of FEL.

In this paper, the analytical solutions of equations of electron betatron motion are derived by W·K·B method for parameters of varyable B_wand γ. with the formula, the reasons that electrons run out of the waveguide are analyzed. Meanwhile, we have compared the analytical results with those which are simulated by WAGFEL code Under certain conditions, analytical results coincide with simulation results well.

A 3-dimensional numerical simulation code for microwave FEL in which space-charge force have been in eluded approxi matelv is worked out. The code constitutes of the electrons' energies and pandermotive phases according to the averaged single-particle equations derived by KMR, and the fields according to the paraxial wave equation. The particle motion is fully three-dimensional. The field solver is accurately three-dimensional for microwave simulation. The simulated results show that longitudinal space-charge force reduce the gain and saturation power about 15%,and increase the synchrotron period of the electrons.

From Single Particle theory, we derived Simulant equations with rectangular waveguide and obtained calculating formulas of TEmn and TMmn mode.Under the same conditions of calculation, it was shown that the results of the reduced one dimension is the same as those of one dimension.Our results are relatively near to LLNL's when only TE₀₁ mode is considered.With the two dimension code FEL-2-A on the basis of investigating its reliability,we analysed the effect on total output power by wtggler field of different linearly polarized,optical field and electron beam parameters under the conditions of constant wig-gler and different linearly polarized wiggler.These preliminary results will be of some reference value to design and experiment of low energy FEL amplifier.