Monte-Carlo simulation module for Lidos.RFQ.designer code

Abstract

New criteria arise when high-current CW linacs are considered. The main requirements for such linacs are maximal RF intensity reduction, very small beam losses.Minimization of CW beam losses in RFQ linac places more stringent requirements upon beam perturbations. Instrumental errors in vane manufacturing, installation and adjustment are sources of such perturbations. Even with very small cell parameter deviations the potential of such perturbations is high enough both for beam transmission reduction and beam quality degradation. A reason enough to such statement is provided by the fact that trajectories even for "ideal" (without perturbations) RFQ channel are spaced in the immediate vicinity of vane surfaces.Hence to choose RFQ channel optimal parameters random perturbation influence have to be taken into account and estimation of tolerances must be given. The goal of the LIDOS.RFQ.Designer package [1-5] development is to help user to solve this problem. It will be recalled that the package contains codes with three levels of mathematical model complexity.The first-level codes make only a preliminary choice of the main parameter arrays on the basis of a simplified physical model. These codes are richly supplied with visual information that helps to find the best linac version quickly. Separate algorithm branch allows using output parameter table obtained by PARMTEQ codes as initial informationThe second-level codes are used for channel data calculations with the real shape of the RFQ vanes and real RF fields. Information from the first level codes is used here as input data.The third-level codes are based on information from the first and second level codes and on complex PICmodels that are needed for a correct beam simulation in the chosen channel version.New version of the package contains the fourth level -"Statistics". Random realizations of channel taking into account deviations of vanes from their ideal positions are generated. From cell to cell the random deviations are statistically independent. To compute the position of vane surface we base on the parameters: r -the distance from axis to cell beginning, m -vane modulation and L -cell length. With perturbations the parameter r is changed over a random value ∆. For cell numbered k we use k k k r r = +∆ %