ICAP 2002 Abstracts and Posters

A Parallel Code for Lifetime Calculations in P/P- Storage Rings in the Presence of Parasitic Beam-Beam Crossings

Abstract

When two beams of charged particles share the same beampipe, traveling in opposite directions, nonlinear forces are introduced due to the presence of beam-beam forces. These forces may excite incoherent resonances, eventually leading to particle loss and thus to a finite beam lifetime. Beam-beam interaction will occur as head-on collisions in the designated interaction points of the machine as well as as parasitic crossings along the circumference of the machine. In the case of protons, damping mechanisms are absent; this can lead to very long time scales for the dynamics of this system.

We developed a code which models a proton/anti proton storage ring as a sequence of symplectic transformations due to the lattice and momentum kicks due to weak-strong beam-beam interaction. The relevant information for the setup is extracted from a MAD description file of the machine and translated to speed-optimized C++ code. By distributing test particles onto computers running in parallel, we are able to track them for a relatively long time: On a 64-processor cluster, and for a storage ring with ~100 parasitic crossings, we are able to calculate beam lifetimes in the range of several hours. We present typical results and discuss possible applications.

Y. Cai, A. Kabel, SLAC

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