Theoretical Studies Of Dielectric Particle Accelerating Structure

The great demands of high-energy physics, LASER, medicine and material science have spurred research into developing a new generation of compact low-cost tabletop particle accelerators with widespread applications in various fields. Particle acceleration by stimulated emission of radiation (PASER) is one of the most promising ways to achieve this goal. In PASER, energy stored in an active medium is transferred directly to the electrons traversing the medium, and therefore, accelerating the former. PASER does not need high power beam driver, and thus neither phase matching nor compensating for phase slippage is required.Based on the basic theory study made by Levi Schachter and coworkers, in this dissertation we theoretically analyzed and evaluated the accelerating field, energy gain and distribution of the bunch moving in the active medium in PASER.Firstly, we analyzed the PASER concept and derived the wake generated by a bunch of electrons moving in an active medium, and then the PASER processin CO2mixture active medium and ArF gas active mediumwas calculated respectively. Our results show that the accelerating gradient can reach1GV/m and even higher when ionization occurs.In the PASER, efficient interaction occurs when a train of micro-bunch whose periodicity being identical to the resonance frequency of the medium,so the bunched electrons will be enhanced the process. The previous theoretical calculations based on the simplified model considering only the energy exchange in the boundless condition, for the experimental condition, however, the gas active medium must be guided by the metal waveguide. In this work, we made detailed analysis on the beam wave interaction in waveguide boundary for the first time. The results show that the energy density could be optimized to a certain value to get the maximum energy exchange. In order to modulate the electron bunch to make enhanced interaction between the electrons and the active medium, Levi Schachter and coworkers suggested a novel paradigm that relies on the possibility that non-relativistic electrons confined by a penning trap will experience collisions of the second kind, leading to bunching of part of the electrons at the resonant frequency of the active medium. Based on the1D solid model made by Levi Schachter and considering the difference between the solid and gas active medium, we modified the formula and simulated the process when the gas mixture active medium is incorporated in the panning trap, and the results show that the electrons can be bunched in thegas mixture active medium in incorporated in the panning trap, and the gas active medium need lower population inversion to bunch the electronsthan the solid active medium, which could facilitate the experimental condition.Moreover, in thisdissertation, anew type accelerating structure was analyzed and calculated, which stands for a composite accelerating cavity utilizing a resonant, periodic structure with a dielectric sphere located at a spherical conducting cavity center. The resonator design is of the whispering gallery type to take advantage of the excellent electromagnetic field confinement offered by this geometry.We made optimization design with the present9.37GHz power source and made calculations with the low loss sapphire dielectric, the results show that all field components at the metallic wall are either zero or very small in this proposed spherical cavity, so one can expect the cavity to be less prone to electrical breakdowns than the traditional cavity. And moreover, it’s quality factor is much larger than that of the traditional accelerators.The work in this dissertation may provide a theoretical reference for the future study in the PASER experiment and resonantspherical cavity.