An interactive beam line simulator module for RHIC

This paper describes the interactive simulation engine, BL, designed for the RHIC project. The program tracks as output to shared memory the central orbit, Twiss and dispersion functions, as well as the 6×6 beam hyperellipsoid. Transfer matrices between elements are available via interactive requests. Using a 6D model, optical elements are modeled with a linear transfer matrix and a vector. The vector allows simulation of misalignments, shifts in field strengths, and beam rigidity. Currently only a linear model is used for elements. In addition to the usual magnets, a foil element is included which can shift the beam´s rigidity (resulting from a change of charge and energy loss), as well as increase the momentum spread and emittance. Running as a Glish client, BL can be interfaced to other programs, such as an orbit plotter and a power supply application to give a quick prediction of the beam orbit from actual operating currents in the accelerator. Various strengths and offsets may be changed by sending Glish events to BL