The time-resolved electron beam envelope parameters, including cross sectional distribution and beam centroid position, are very important for the study of beam transmission characteristics in a magnetic field and for...The time-resolved electron beam envelope parameters, including cross sectional distribution and beam centroid position, are very important for the study of beam transmission characteristics in a magnetic field and for verifying the rationality of the magnetic field parameters employed. One kind of high time-resolved beam envelope measurement system has recently been developed, constituted of a high-speed framing camera and a streak camera. It can obtain three panoramic images of the beam and time continuous information along the given beam profile simultaneously. Recently obtained data has proved that several fast vibrations of the beam envelope along the diameter direction occur during the front and the tail parts of the electron beam. The vibration period is several nanoseconds. The effect of magnetic field on the electron beam is also observed and verified. Beam debugging experiments have proved that the existing beam transmission design is reasonable and viable. This beam envelope measurement system will establish a good foundation for beam physics research.展开更多
We study an intense beam propagating through the double periodic focusing channel by the particle-coremodel,and obtain the beam envelope equation.According to the Poincare-Lyapunov theorem,we analyze the stabilityof b...We study an intense beam propagating through the double periodic focusing channel by the particle-coremodel,and obtain the beam envelope equation.According to the Poincare-Lyapunov theorem,we analyze the stabilityof beam envelope equation and find the beam halo.The soliton control method for controlling the beam halo-chaos isput forward based on mechanism of halo formation and strategy of controlling beam halo-chaos,and we also prove thevalidity of the control method,and furthermore,the feasible experimental project is given.We perform multiparticlesimulation to control the halo by using the soliton controller.It is shown that our control method is effective.We alsofind the radial ion density changes when the ion beam is in the channel,not only the halo-chaos and its regeneration canbe eliminated by using the nonlinear control method,but also the density uniformity can be found at beam's centre aslong as an appropriate control method is chosen.展开更多
We revisit finite element method of modeling multi-scale photonic/electromagnetic devices via the proposed beam basis function,in combination with domain decompositions.Our approach ensures mathematical and physical c...We revisit finite element method of modeling multi-scale photonic/electromagnetic devices via the proposed beam basis function,in combination with domain decompositions.Our approach ensures mathematical and physical consistency,can also handle multi-scale computational tasks efficiently with the assistance of the damping block-Jacobi iterative solver.By implementing the first-order Robin transmission condition at the interfaces between neighboring subdomains and introducing the dual“current”vari-ables,we can significantly reduce the computational burden and communication data volume during the iterative solving process.The theoretical foundation and detailed implementation procedures are presented,accompanied with two representative examples.The first example is a refractive-diffractive hybrid optical system with feature size contrast up to 104,while the second example is the free surface optical system wherein the geometric ray tracing algorithm is inadequate.The obtained results for the two examples show excellent agreement with the standard finite element method(standard FEM)with significantly reducing the number of meshes required for computation and memory usages to nearly one-fifth.Since the computational time is inversely proportional to the num-ber of decomposed subdomains(N)under the parallel computing configuration,the computational time in our work is approximately 1/3Nreduced to of that using standard FEM for the two examples.展开更多
Further studies on beam emittance measurement have been made to improve the emittance measurement precision at BEPCⅡ linac.Some problems in the measurement are solved and a code for beam emittance calculation is deve...Further studies on beam emittance measurement have been made to improve the emittance measurement precision at BEPCⅡ linac.Some problems in the measurement are solved and a code for beam emittance calculation is developed.With these improvements,the emittance measurement precision was upgraded.展开更多
The design of CSNS MEBT has two objectives：（1） to match the beam both in the transversal direction and the longitudinal direction from RFQ into DTL;（2） to further chop the beam into the required time structure as...The design of CSNS MEBT has two objectives：（1） to match the beam both in the transversal direction and the longitudinal direction from RFQ into DTL;（2） to further chop the beam into the required time structure asked by RCS. It is very diffcult and critical to control well the emittance growth and in the meantime to match and chop the beam. Firstly,the optical design is done and optimized,and the multi-particle simulations show that the maximum emittance growth is successfully controlled within 14%. Secondly,based on the different beam envelopes obtained by TRACE-3D and PARMELA,the least deflecting angle of the chopper is determined by TRACE-3D. At last,the field of steering magnet is determined through simulations.展开更多
基金Supported by National Natural Science Foundation of China(10675104,11375162)
文摘The time-resolved electron beam envelope parameters, including cross sectional distribution and beam centroid position, are very important for the study of beam transmission characteristics in a magnetic field and for verifying the rationality of the magnetic field parameters employed. One kind of high time-resolved beam envelope measurement system has recently been developed, constituted of a high-speed framing camera and a streak camera. It can obtain three panoramic images of the beam and time continuous information along the given beam profile simultaneously. Recently obtained data has proved that several fast vibrations of the beam envelope along the diameter direction occur during the front and the tail parts of the electron beam. The vibration period is several nanoseconds. The effect of magnetic field on the electron beam is also observed and verified. Beam debugging experiments have proved that the existing beam transmission design is reasonable and viable. This beam envelope measurement system will establish a good foundation for beam physics research.
基金National Natural Science Foundation of China under Grant Nos.10247005 and 70071047the Scientific Research Foundation of China University of Mining and Technology for the Young Teachers under Grant No.OK060119
文摘We study an intense beam propagating through the double periodic focusing channel by the particle-coremodel,and obtain the beam envelope equation.According to the Poincare-Lyapunov theorem,we analyze the stabilityof beam envelope equation and find the beam halo.The soliton control method for controlling the beam halo-chaos isput forward based on mechanism of halo formation and strategy of controlling beam halo-chaos,and we also prove thevalidity of the control method,and furthermore,the feasible experimental project is given.We perform multiparticlesimulation to control the halo by using the soliton controller.It is shown that our control method is effective.We alsofind the radial ion density changes when the ion beam is in the channel,not only the halo-chaos and its regeneration canbe eliminated by using the nonlinear control method,but also the density uniformity can be found at beam's centre aslong as an appropriate control method is chosen.
文摘We revisit finite element method of modeling multi-scale photonic/electromagnetic devices via the proposed beam basis function,in combination with domain decompositions.Our approach ensures mathematical and physical consistency,can also handle multi-scale computational tasks efficiently with the assistance of the damping block-Jacobi iterative solver.By implementing the first-order Robin transmission condition at the interfaces between neighboring subdomains and introducing the dual“current”vari-ables,we can significantly reduce the computational burden and communication data volume during the iterative solving process.The theoretical foundation and detailed implementation procedures are presented,accompanied with two representative examples.The first example is a refractive-diffractive hybrid optical system with feature size contrast up to 104,while the second example is the free surface optical system wherein the geometric ray tracing algorithm is inadequate.The obtained results for the two examples show excellent agreement with the standard finite element method(standard FEM)with significantly reducing the number of meshes required for computation and memory usages to nearly one-fifth.Since the computational time is inversely proportional to the num-ber of decomposed subdomains(N)under the parallel computing configuration,the computational time in our work is approximately 1/3Nreduced to of that using standard FEM for the two examples.
文摘Further studies on beam emittance measurement have been made to improve the emittance measurement precision at BEPCⅡ linac.Some problems in the measurement are solved and a code for beam emittance calculation is developed.With these improvements,the emittance measurement precision was upgraded.
文摘The design of CSNS MEBT has two objectives：（1） to match the beam both in the transversal direction and the longitudinal direction from RFQ into DTL;（2） to further chop the beam into the required time structure asked by RCS. It is very diffcult and critical to control well the emittance growth and in the meantime to match and chop the beam. Firstly,the optical design is done and optimized,and the multi-particle simulations show that the maximum emittance growth is successfully controlled within 14%. Secondly,based on the different beam envelopes obtained by TRACE-3D and PARMELA,the least deflecting angle of the chopper is determined by TRACE-3D. At last,the field of steering magnet is determined through simulations.
