Computer simulation of the space charge dominated beam dynamics for external injection into the JINR Phasotron
A project of increasing the beam intensity of the 660 MeV JINR proton Phasotron up to 50 µA by an external injection of the H − beam with energy of 5 MeV is now under design. Computer simulation of the space charge dominated beam dynamics in Phasotron is reported. As follows from the simulation, the capture efficiency does not change too much when the beam space charge is taken into account.
EXTERNAL INJECTION INTO PHASOTRON ( COMPUTER SIMULATION )
The paper summarizes the computer simulation data of the beam capture in acceleration at the external injection into the JINR Phasotron (Fig.1) for the injection energies 1.5, 3.0 and 5.0 MeV. The simulation takes into account the particle starting phase and injection time, the horizontal and axial beam emittances and the influence of the particle scattering by foil on the increase in the axial emittance. Simulation is fullfilled for the experimental magnetic field and RF program. Calculation shows the 15% capture efficiency for the injection energy 1.5 MeV and 24% for 5.0 MeV (the particle injection time of 80 µs).
Analysis of Cyclotron-Type Electric Lenses and the Effects of Posts
The focusing properties of cyclotron-type electric lenses with time-varying potentials were investigated by analytical and numerical methods. First-order focusing formulas were derived which include the effects of "liner" and of focusing grids. The main emphasis of the numerical studies was on the aspects of lens effects which had not been previously investigated: (a) The behavior of the lenses at large transit times or rf frequencies for which the approximations of analytical theory are not valid. (b) The effects of posts (or grids) placed at one or both sides of the gap. The lens parameters, i.e. focal lengths and location of principal planes, were computed numerically for several geometries using electric field data obtained by computer with relaxation method. Computations were carried out for several two-dimensional and three-dimensional gap geometries at three different frequencies of the gap voltage as a function of kinetic energy and rf phase of the particles at the center of the gap. A criterion for the validity of first-order theory was established. The application to cyclotrons is discussed briefly.