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BEAM POSITION MONITOR SYSTEM FOR THE ORBIT FEEDBACK AT THE INTERACTION REGION OF KEKB

To maintain the optimum collision condition of the two rings, two special BPMs with 8-button electrodes, called OCTPOS, were installed inside the super-conducting quadrupole magnets (QCSs) at the interaction region (IR) of KEKB. Four normal BPMs with 4-button electrodes were incorporated outside the QCSs. We have commissioned the OCTPOS BPMs for simultaneous measurements of both the electron and positron beam positions from their composite signal. We have verified the separation of both beams by the finite orbit separation method. The beam positions of OCTPOS and four normal BPMs were consistent. This report describes the performance of the system as a result of operation.