Application of PIC method for z-code and t-code simulation in RFQ accelerators

The 2D PIC (Particle in cell) method, widely used in the calculation of space charge effect for particle dynamic simulations is described. The difference between t-code (Using time as independent variable) and z-code (Using longitudinal position as independent variable) is illuminated. For single beam acceleration and positive-negative ion beams acceleration, simulation results of the transmission rate using t-code and z-code are provided, respectively, with the structure parameters of the RFQ (Radio frequency quadrupole) accelerator in the Clean Nuclear Power Project of Major State Basic Research Development Program. The results show that when the phase spread or energy spread of the bunch is large, relatively large errors could be introduced in z-code during the calculation of space charge effect. Therefore t-code should be adopted instead in the dynamic simulations for more accurate results. (authors)