Synthesizing a four-dimensional beam particle distribution frommultiple two-dimensional views

Friedman, A. ; Grote, D. P. ; Celata, C. M. ; Staples, J. W.

Lawrence Berkeley National Laboratory

关键词: Phase Space;    Longitudinal Momentum;    Particle Beams;    32 Energy Conservation, Consumption, And Utilization;    Monte Carlo Method;   

DOI  :  10.2172/881378
RP-ID  :  LBNL--49647
RP-ID  :  DE-AC02-05CH11231
RP-ID  :  881378

美国|英语

来源: UNT Digital Library

【 摘 要 】

The transverse dynamics of a nearly-monoenergetic particle beam are described by the evolution of the 4D distribution f(x,y,x',y'), where x and y are the transverse spatial coordinates and x' {triple_bond} p{sub x}/p{sub z} and y' {triple_bond} p{sub y}/p{sub z} are the corresponding momentum components divided by the longitudinal momentum component. In present-day experimental practice, such beams are often diagnosed by passing them through an axially-separated pair of slits parallel to the y axis. This selects for x and x' and integrates over y and y'. A sequence of pulses (with the slits at various x positions) yields a 2D projection of the beam phase space, f(x,x'). Another scanner might yield f(y,y') or, using crossed slits, f(x,y). The challenge is that a small set of such 2D scans does not uniquely specify f(x,y,x',y'); correlations in planes other than those measured are unknown. We have developed Monte-Carlo methods and formulated physically-motivated constraints to synthesize a ''reasonable'' set of particles having 2D projectional densities consistent with the experimental data. Such a set may be used to initialize simulations of the downstream beam. The methods and their performance on model problems are described.