The Space Charge Computer Program SCHAR

The space charge computer program SCHAR uses macrofilaments or macroparticles to model the effects of space charge in ion transport. The program calculates the transport properties of beams of non-relativistic charged particles using two alternative macroparticle formulations. The line mode formulation considers the beam to be composed of a manageable number of infinitely long charged filaments. The paths of these filaments are fixed in time but their positions as a function of distance along the line are determined by a fourth-order Runge-Kutta time step integration. The point mode formulation considers the beam to be composed of a manageable number of charged macroparticles. These macroparticles have the same charge-to-mass ratio as the actual particles. In this mode the space charge effects are modeled solely by the Coulomb repulsion of the macroparticles. In space charge cases, while the calculation steps from SCHAR are identical, the line mode will run by a factor of two or three times faster than the point mode; if beam bunching occurs, however, use of the line mode becomes inappropriate. Both modes are described by SCHAR in a left-handed Cartesian coordinate system. Among the optional methods for spreading out the filaments or particles in phase space are: four-volumemore » distribution, designed for line mode operation; KV distribution, a specialized four-dimensional input assumed also by TRACE; six-volume distribution, meant for point mode but also applicable to line mode operation; and ''observed'' distribution, designed for point mode operation.« less