The Mechanical Design Of The Beam Position Monitor In Accelerator And The Study On Its Controlling System

This master’s thesis is based on the requirement of the project, the design of the mechanical system of target lifting mechanism and adjustable slit mechanism, of IHEP of CAS. In order to obtain the practical need of electron beam for the accelerator system so as to enter the target chamber to make bombardment experiments, it is necessary to use several adjustable slits to filter the focused electron beam and reduce the impulse strength of the electron beam. Finally, we get the needed quasi individual electron. Because of the extremely weak current electron linear accelerator e-gun outlet’s electron beam intensity is in microamp level, at this time the number of electrons in each of the pulse beam current is still relatively numerous.To reduce the impulse strength of the electron beam, several adjustable slits should be used to control the number of electrons which flow through the acceleration section. Each adjustable slit’s controllability is different, but the ultimate goal is to reduce the number of electrons to quasi individual electron. In order to adjust the width of the slit accurately, it is required that adjustable slit mechanism ’s each step of the adjustment of step length is 5μm,by the selection of a high performance stepper motor to achieve this requirement. And whether the electron beam that through the adjustable slit is quasi individual electron, which needs to be tested by target lifting mechanism. When measuring beam current intensity and electron number, the target lifting mechanism is a vacuum in-out mechanism with measuring probe, which can make probe realize the reciprocating motion under the driving of stepper motor. In order to achieve a higher repeatability, the reset accuracy of the target lifting mechanism must reach 0.02 mm.According to the project requirements, in this paper, a mechanical system of beam position monitor(BPM) in accelerator is designed by using the modern design method, and at the same time, its control system is studied.First of all, in this paper the application of the finite element analysis method in the design of the mechanical system is introduced, and emphatically the key bearing parts of the target lifting mechanism in BPM are carried out by the strength analysis and verification, and the Inventor’s own ANSYS module provides a theoretical basis for the mechanical design and improvement of the BPM.Secondly, in order to make the system can perform the function of the three-dimensional regulation of±15mm, in this paper the author respectively carries on the modeling and optimization design for the mechanical system of the a djustable slit mechanism and the target lifting mechanism by using the Inventor software’s special advantage in the solid modeling and the high efficiency of engineering drawing generation, etc. And after repeated optimization design, a set of three-dimensional adjustment mechanism is finally designed. When in the design of the modeling and optimization, the material utilization, the manufacturing costs, the process and assembly technique and other important factors are all taken into account, which makes the design of BPM more reasonable.In addition, the driving device hardware system of the BPM is emphatically designed in this paper. Completed the driving device model, and combined with the actual working conditions, the stepper motor as driving element u sed in the linear mobile mechanism of mechanical system is made a detailed analysis of calculation and selection of the confirmation. And according to the project requirements, a reasonable selection of the stepper motor driver is made, at the same time completed the selection to confirm the position feedback device components.Finally, in this paper, theoretical research is studied on the control system of the mechanical system. And on the basis of all the above work, control tasks of the control system are determined. According to the control tasks, the control system is built, the working principle of the realization for the control tasks is explained. Finally, the step of adjustable slit mechanism reaches 5μm, the target of the lifting mechanism repeat positioning accuracy reaches 0.02 mm.