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Jia Qika

Publications and source records attributed to Jia Qika.

3 recordsLinked to original sources

Particle acceleration by stimulated emission of radiation in cylinder waveguide

In the particle acceleration by stimulated emission of radiation (PASER), the efficient interaction occurs when a train of micro-bunches whose periodicity being identical to the resonance frequency of the medium. The previous theoretical calculations based on the simplified model consider only the energy exchange in the boundless condition, under the experimental condition, however, the gas active medium must be guided by the metal waveguide. In this paper, we have developed the model of energy exchange between a train of micro-bunches and gas mixture active medium in waveguide boundary for the first time based on the Theory of Electromagnetic Fields, and made detailed analysis and calculations with MathCAD. The results show that the energy density could be optimized to a certain value to get the maximum energy exchange.

physics.acc-ph

Optimization of single-step tapering amplitude and energy detuning for high-gain FELs

We put forward a method to optimize the step-tapering amplitude of undulator strength and initial energy detuning of electron beam with the goal of maximizing the saturation power of high-gain FELs, based on the physics of longitudinal electron beam phase space. Using the FEL simulation code GENESIS, we numerically demonstrate the accuracy of the estimation for parameters corresponding to the linac coherent light source and the Tesla test facility.

physics.acc-ph

An analysis on optimization of undulator in self-seeding free electron laser

A simple analysis is given for optimum length of undulator in self-seeding free electron laser (FEL). The obtained relations show the correlation between the undulator length and the system parameters. The power required for the seeding in the second part undulator and overall efficiency to monochromatizating the seeding settle on the length of the first part undulator; the magnitude of seeding power dominates the length of the second part undulator; the whole length of the undulators in self-seeding FEL is determined by the overall efficiency to get coherent seed, it is about half as long again as that of SASE, not including the dispersion section. The requirement of the dispersion section strength is also analyzed.

physics.acc-ph