Fast Transverse Beam Instability Caused by Electron Cloud Trapped in Combined Function Magnets

LIST OF FIGURES ......................................................................................................................................... iii LIST OF TABLES ........................................................................................................................................... vi ACKNOWLEDGEMENTS ......................................................................................................................... vii ABSTRACT ....................................................................................................................................................... ix 1 ELECTRON CLOUD IN PARTICLE ACCELERATORS ................................................................. 1 1.1 Electron cloud build-up .......................................................................................................................... 3 1.2 Electron cloud instabilities ................................................................................................................... 12 1.3 Electron cloud tune shift ...................................................................................................................... 15 1.4 Beampipe conditioning ......................................................................................................................... 17 2 BEAM DYNAMICS MEASUREMENTS OF THE FAST INSTABILITY ................................... 20 2.1 Beam manipulation and diagnostics ................................................................................................... 20 2.2 Dynamics of the unstable beam .......................................................................................................... 26 2.3 Beam stabilization by a clearing bunch .............................................................................................. 35 3 MICROWAVE MEASUREMENT OF THE CLOUD DENSITY .................................................. 43 3.1 Experimental setup ............................................................................................................................... 44 3.2 Schottky noise ........................................................................................................................................ 50 3.3 Measured electron cloud density ......................................................................................................... 56 4 NUMERICAL SIMULATION ................................................................................................................. 59 4.1 Electron cloud trapping in a combined function magnet ............................................................... 60 4.2 Numerical model ................................................................................................................................... 65 4.3 Electron cloud build-up ........................................................................................................................ 68 4.4 Electron cloud instability ...................................................................................................................... 81 5 ANALYTICAL MODEL OF THE ELECTRON CLOUD INSTABILITY .................................. 87 5.1 Model of the beam-cloud interaction ................................................................................................. 87 5.2 Fast instability in Recycler .................................................................................................................... 92 5.3 Instability at higher intensities ............................................................................................................. 96 5.4 Landau damping of the fast instability using octupoles ................................................................... 97 6 CONCLUSION ......................................................................................................................................... 102 REFERENCES............................. Mehr