EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH CERN-SL-Note-2002-017 (AP) Accelerator Physics Studies for KEKB: Electron Trapping, Electron Cloud in the HER, Closed-Orbit Drift, Horizontal Instability and Tune Shift

In this report, I address 4 different items: (1) the trapping of electrons in a quadrupole field, (2) the electron-cloud build up inside an HER dipole magnet, (3) the closed orbit drift with SVD correction, and (4) the transverse tune shifts and horizontal instability in the HER. The appendix presents preliminary electron-cloud simulations for the two JKJ rings. Geneva, Switzerland May 13, 2002 1 Electron Trapping Simulations by L. Wang [1] indicate that a large number of cloud electrons remain trapped inside a quadrupole field, thereby surviving for an arbitrarily long gap between bunch trains. We here examine whether this result can be reproduced by the code ECLOUD [2]. Ignoring the local field variation (over a cyclotron radius), the trapping condition is [3, 4] (1) where denotes the total electron velocity ! "$# (2) For simplicity, we only consider the case of a uniform quadrupole field and round beam pipe. Then, the square of the transverse velocity (i.e., transverse to the field) is