Author: Zhang, L.H.
Paper Title Page
THPAB202 Problem and Solution with the Longitudinal Tracking of the ORBIT Code 4176
 
  • L.H. Zhang, J.Y. Tang
    IHEP, Beijing, People’s Republic of China
  • Y.K. Chen
    IHEP CSNS, Guangdong Province, People’s Republic of China
  • L.H. Zhang
    University of Chinese Academy of Sciences, Beijing, People’s Republic of China
 
  The ORBIT code has been widely used for beam dy­nam­ics sim­u­la­tions in­clud­ing in­jec­tion and ac­cel­er­a­tion in high-in­ten­sity hadron syn­chro­trons. When the ORBIT’s 1D lon­gi­tu­di­nal track­ing was em­ployed for the ac­cel­er­a­tion process in CSNS/RCS, the lon­gi­tu­di­nal emit­tance in eV-s was found de­creas­ing sub­stan­tially dur­ing ac­cel­er­a­tion, though the adi­a­batic con­di­tion is still met dur­ing this process. This is against the Li­ou­ville the­o­rem that pre­dicts the preser­va­tion of the emit­tance dur­ing ac­cel­er­a­tion. The re­cent ma­chine study in the ac­cel­er­a­tor and the sim­u­la­tions with a self-made code demon­strate that the lon­gi­tu­di­nal emit­tance is al­most in­vari­ant, which fur­ther in­di­cates that the ORBIT lon­gi­tu­di­nal track­ing might be in­cor­rect. A de­tailed check-over in the ORBIT code source finds that the lon­gi­tu­di­nal fi­nite dif­fer­ence equa­tion used in the code is er­ro­neous when ap­plied to an ac­cel­er­a­tion process. The new code for­mat Py­OR­BIT has the same prob­lem. After the small sec­ondary fac­tor is in­cluded in the code, ORBIT can pro­duce re­sults keep­ing the lon­gi­tu­di­nal emit­tance in­vari­ant. This paper pre­sents some de­tails about the study.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB202  
About • paper received ※ 14 May 2021       paper accepted ※ 01 July 2021       issue date ※ 21 August 2021  
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