Key Physical Issue Study And3Dimensional Numerical Simulation Algorithms Research On Linear Induction Accelerator

Linear induction accelerators (LIA) are constructed to produce relativistic intenseelectron beams with high energy and high qualities. Researching on linear inductionaccelerator by numerical method has been widely used abroad. However, best PICsoftware is embargo for us. University of Electronic Science and Technology of Chinacooperated with Institute of Fluid Physics, China Academy of Engineering Physics toresearch on linear induction accelerator about key physical issue and numericalsimulation algorithms.1. To research photoemission injector, photoemission module is researched anddeveloped firstly. In the photoemission module, photocathode material and laser sourceare taken into account. A relationship between photocathode and macro particle initialcondition is established. Then a photoemission injector is modeled to simulatephotoemission process. Some of the simulation result is coincident with experiment.The deviation of current density between experiment and simulation is less than7%.And the emittance of photoemission injector beams is smaller than cold emission;Multi-function emission module is researched and developed, which could set beamparameter not only energy, charge, but also emittance, energy spread and beam off-axis;2. Steering magnetic field matching with solenoid magnetic field is researched. Toresearch this physical issue, solenoid magnetic field and steering magnetic field moduleare developed firstly. When research solenoid magnetic field, solenoid axis tilt anduniform ring are taken into account. Then researching shows how to adjust and matchthem together. This research could guide researchers how to adjust steering coil currentin experiments. Steering magnetic field has another function, which could adjust beamcentroid. This physical process is researched also. In the research, multi-functionemission module is used for emit tilt beam, and try to adjust steering coil current toadjust beam centroid. The beam centroid adjusted at last;3. To research wakefield and beam transmission, two kinds accelerator cell moduleare developed. The difference between two kinds accelerator cell module is the shape ofthe accelerator gap. The accelerator gap is the most important place on researchwakefield, which could excite certain frequency wakefield. The wakefield aroundaccelerator gap are integrated and analyzed. The simulation result shows that the current gap boundary condition isn’t suitable for research wakefield. If the gap boundarycondition set as electric boundary, that would be perfect for research wakefield. In thenext study, the method of input accelerator field must choose other option. Under thissituation, electric boundary condition could be set at accelerator gap;4. Beam transmission process in the main accelerator system is researched. Andthis is the very first time researched main accelerator by numerical method in domestic.The main accelerator system is about40meters long. Based on the platform of theMPICH2message passing system, a proper method for parallel computing of moreaccelerate sections is provided and solved LIA’s great scale problems. It cost6personalcomputers,3days to simulate beam transmission in main accelerator. The simulationgot two important result are coincident with experiment:1. The waveform of beam atcertain position is fixed, which wouldn’t change vary time;2. After transmission mainaccelerator, beam energy reached20.2MeV. By the way, the simulation got a group ofmatch fields under certain condition;5. Beam transmission in downstream is researched also. Magnetic lens areresearched by magnetic scalar and vector method firstly. Each method has its advantageand disadvantage. The algorithm of magnetic scalar method is simpler than vectormethod. That when set parameters, vector method is much more complicate. But ifpermeability of magnetic lens is smaller than4000, vector method is more proper forsimulation magnetic field. When researching beam transmission in downstream,magnetic vector method is applied. Then build downstream module and set magneticfield to simulate and research beam transmission. The beam focused to a3.9mm spot inthe simulation. For future research, quadrupole lens module are researched anddeveloped also.